Category: forest pathogens

Eight Hawaiian birds: gone forever

large Kaua’i thrush; specimen photographed by Huub Veldhuizen van Zanten / Naturalis Biodiversity Center; via Wikimedia commons

I usually blog about tree pests but the bioinvasion disasters in Hawai`i and Guam also attract my attention. I have blogged in the past about insect or pathogen threats to Hawaiʻi’s ‘ōhi‘a trees and other native plants of Hawaiʻi and Guam.

Some of the most difficult and tragic of the invasive species threats in Hawaiʻi are avian diseases vectored by introduced mosquitos. Avian pox and especially avian malaria have already caused extinction of numerous bird species, and continue to threaten many of the remaining endemic species.

I regret that it takes extinction to bring overdue attention to the threats to Hawaiian birds. The USFWS has proposed to remove eight species of Hawaiian birds and one from Guam from the list of endangered species because they are extinct.  

[If you prefer to see living birds, visit here.]

Distressing as is the current determination of extinctions, it is just the tip of iceberg. Since people colonized the Hawaiian Islands 1,500 years ago, 71 bird species have become extinct, 48 before the arrival of Europeans and 23 since Captain James Cook’s arrival in 1778. Historically, more than 50 different honeycreepers lived in Hawaiʻi; today, only 17 species remain. Eight of these have been federally listed as endangered or threatened under the Endangered Species Act. A ninth bird species – a flycatcher – also has been listed. Another honeycreeper, i`iwi (Drepanis (Vestiaria) coccinea) is listed as threatened on Kauaʻi. As noted, the USFWS now says eight of these species (six honeycreepers, an ʻĀkepa, and one thrush) are actually extinct.

FWS will accept comments received or postmarked on or before November 29, 2021. To have an impact, comments must be substantive, not just a statement of support or opposition. The USFWS action includes 14 other species, among them the ivory-billed woodpecker, Bachman’s warbler, a bat, fish, and freshwater mussels.

Maui nakupu’u specimen photographed by Huub Veldhuizen van Zanten / Naturalis Biodiversity Center; via Wikimedia Commons

In describing the threats to the Pacific Island birds, the USFWS proposal focuses on non-native diseases, specifically avian pox and avian malaria. USFWS also mentions introduced vertebrates – especially predators such as cats, rats, and mongoose; and invasive plants. Because it does not deal with those bird species that continue to exist, the notice does not mention prospective threats. For example, constant vigilance is needed against possible introduction (from Guam) of the brown tree snake. Also needed is a strategy to counter rapid ‘ōhi‘a death, which threatens widespread mortality of the ‘ōhi‘a lehua tree (Metrosideros polymorpha).

I`iwi feeding on ohi’a in Hakalau Forest NWR, Hawai’i; photo by Daniel J. Lebbin, American Bird Conservancy

The USFWS proposal describes significant efforts over the past 50 years to restore bird species, including implementation of two recovery plans and numerous surveys trying to find remnant populations. However, none of these projects could counter the effects of the mosquito-vectored pox virus (Avipoxvirus) and avian malaria (Plasmodium relictum). The primary vector, Culex quinquefasciatus, was introduced to the islands in 1826. It has already reached the 6000 feet elevation level. Two other mosquitoes, Aedes albopictus and A. aegypti, may also spread avian pox.  The former has been present in Hawai`i since 1896. The Aedes mosquitoes are – so far – at elevations of ~4,000 feet. However, they are expected to spread higher as the climate warms. The Hawaiian honeycreepers (subfamily Drepanidinae) are highly susceptible to these diseases. As a result, many of these bird species have disappeared from areas below ~ 4,500 feet (1,372 meters) over the last century.

One result of climate change is that mosquitoes are now able to penetrate even higher, up to 6000 feet. Only the islands of Hawai`i (the Big Island) and Maui have forests above this higher elevation.

The descriptions of the eight species purported to be extinct demonstrates the impact of many threats, but especially the diseases. Of the eight species, four are found on the island of Kauaʻi. Three were listed as endangered in 1967, when the U.S.’ first endangered species law came into force. The fourth was listed just a few years later, in 1970. The highest elevation on Kauaiʻ is 5,100 feet.

  • Kauaʻi ʻakialoa (Akialoa stejnegeri) listed (as Hemignathus stejnegeri) in 1967, about the time of the last confirmed observations. The species used to be widespread on Kauaʻi and occupied all forest types above 656 feet (200 meters).
  • Kauaʻi nukupuʻu (Hemignathus hanapepe) listed as endangered in 1967. At the time of listing, only two individuals had been reported during the 20th Century. The original extent of its geographic range is unknown.
  • Kauaʻi ‘o‘o (Moho braccatus) listed as endangered in 1967. At the time of listing, the population size was estimated at 36 individuals. The last plausible record was a vocal response to a recording in 1987. Its last known habitat was the dense ‘ōhi‘a lehua forest in the valleys of Alakaʻi Wilderness Preserve. It reportedly fed on various invertebrates and the fruits and nectar from ‘ōhi‘a lehua, lobelia, and other flowering plants. The original extent of its geographic range is unknown. 
  • Large Kauaʻi thrush (Myadestes myadestinus) listed as endangered in 1970. At the time of listing, the population size was estimated at 337 individuals. The last unconfirmed and confirmed sightings occurred in the late 1980s.

Three of the putatively extinct species are found on the island of Maui. Maui’s highest point, Haleakalā, reaches 10,000 feet. Two of these species were listed in 1970. The third was discovered in 1973! This demonstrates how difficult it is to survey dense forests on steep, highly uneven volcanic slopes – especially when the substrate is a’a lava!

  • Maui ʻĀkepa (Loxops coccineus ochraceus) listed (as Loxops ochraceus) in 1970. At the time of listing, its population was estimated at 230 individuals. The Maui ʻĀkepa preys on various insects and drinks the nectar of ‘ōhi‘a lehua flowers and uses the tree for nesting. The original extent of the geographical range is unknown, but thought probably to include Molokai and Lānaʻi. By the late 19th century all reports were from mid- to high-elevation forests; possibly the birds had already succumbed to the mosquito-vectored diseases. However, even recent surveys have been at too low intensity to definitively demonstrate that the species is extinct.
  • Maui Nukupuʻu (Hemignathus lucidus affinis) listed (as Hemignathus affinis) in 1970. It probably formerly inhabited Molokai. Even in the late 19th century observers noted the restricted distribution and low population density of Maui nukupuʻu. The species was rediscovered in 1967 in the upper reaches of Kīpahulu Valley in Haleakalā National Park, East Maui. The last confirmed sighting was in 1996, from the nearby Hanawī Natural Area Reserve
  • Po‘ouli (Melamprosops phaeosoma) listed as endangered in 1975, two years after its discovery. At the time of listing, its population was estimated at 140. Fossil evidence indicated it once had a much broader geographic and habitat range. It foraged on tree branches, preferring several native shrubs and trees, including ‘ōhi‘a lehua. Attempts were made to breed the species in captivity in the early 2000s, but these failed. The last two birds known to exist were last seen in December 2003 and January 2004.
Kipahulu Valley on Maui; photo by Kim and Forrest Starr

The eighth species is from Molokai, which has no elevation higher than 4900 feet.

  • Molokai Creeper (Paroeomyza flammea) listed in 1970.  At the time of listing, the Molokai creeper was considered extremely rare. It gleaned insects from vegetation and bark in wet ‘ōhi‘a lehua, forests. Molokai creeper was common in 1907, but by the 1930s, it was considered in danger of extinction. It was last detected in 1963.

Time is running out for Hawaiʻi’s native birds. In 2016 the USFWS listed yet another Hawaiian honeycreeper, the formerly ubiquitous ʻiʻiwi. (Drepanis (Vestiaria) coccinea), as threatened on Kauaʻi. Conservationists recognize the need to combat the mosquitoes.

While I mourn the recent extinction of several Hawaiian forest birds, I celebrate the decision by Hawaiian-based conservation entities to adopt innovative strategies to counter the invasive species threat.

An Innovative and Bold Initiative

The delisting proposal mentions a hopeful development: creation of a multi-agency consortium called “Birds, Not Mosquitoes”. Participating agencies include the Hawaiʻi Department of Land and Natural Resources, Hawaiʻi Department of Health, U.S. Fish and Wildlife Service, University of Hawaiʻi, U.S. Geological Survey, National Park Service, American Bird Conservancy, The Nature Conservancy of Hawaiʻi, Coordinating Group on Alien Pest Species, Island Conservation, and Pacific Rim Conservation. Also involved are the Kauaʻi Forest Bird Recovery Project, Maui Forest Bird Recovery Project, University of Kentucky, and Michigan State University.

Culex quinquefasciatus PIXNIO

The partnership is exploring methods to suppress the mosquito populations. The current focus is on using a common, naturally-occurring bacteria as a “mosquito birth control”. Many insects, including some mosquitoes, carry a naturally-occurring bacterium, Wolbachia. If male and female mosquitoes of the same species carry different, “incompatible” strains of Wolbachia, the eggs wonʻt hatch. The Incompatible Insect Technique (IIT) currently under consideration would intentionally infect male mosquitoes with a specific strain of Wolbachia. These males would then be released to mate with the wild females – and produce infertile eggs. Male mosquitoes donʻt bite humans or birds; the female needs the blood meal to produce eggs.

This method has been successfully used around the globe to reduce populations of mosquitoes that carry human diseases such as dengue fever and malaria. Because of the conservation crisis, the “Birds, Not Mosquitoes” program is seeking permits to moves the project forward as quickly as possible while also ensuring full compliance with all state and federal requirements. Small trial releases would need to happen first to validate success in the field, with larger landscape-scale releases to follow.

Research in Hawaiʻi that is not part of the multi-agency “Birds not Mosquitoes” project is exploring genetic techniques to control mosquitoes. Any such strategy must meet careful safety standards and be registered with federal agencies and within Hawai‘i before use. Because any genetic technique to control mosquitoes is assumed to be more than a decade away and could face considerable public opposition, it likely would not be available in time to prevent additional extinctions of Hawaiʻi’s endemic forest birds.

The “Birds, Not Mosquitoes program” is a multi-year effort to develop the tool, establish the best approach for deploying the tool, and then sustain the effort to keep invasive mosquito populations suppressed. Success can save at least 12 bird species in Hawai`i from extinction, and benefit many more. Funding needs over the next five years are:

* FY2022 – $3 Million

* FY2023 – $5 Million

* FY2024 – 2026 – $7 Million per year

Please contact your Representative and Senators and urge them to support funding for this effort in the Interior Appropriations bills for the coming years.

SOURCE

DEPARTMENT OF THE INTERIOR Fish and Wildlife Service Endangered and Threatened Wildlife and Plants; Removal of 23 Extinct Species From the Lists of Endangered and Threatened Wildlife and Plants ACTION: Proposed rule. 50 CFR Part 17 Federal Register / Vol. 86, No. 187 / Thursday, September 30, 2021

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

Updates on 4 major invaders + APHIS annual report

As of September 2021, a number of new publications or presentations focus on four major forest pests: the Asian longhorned beetle, emerald ash borer, sudden oak death, and the Asian gypsy moth. Here’s a summary.

Asian longhorned beetle (ALB)  

In many ways, the ALB is the poster child for wood-borers introduced in wood packaging (SWPM). ALB has been transported multiple times in the 30 or more years since the world opened to goods from China. Outbreaks have been detected in ~50 locations in North America, Europe, the Middle East (Trotter 2021, full citation at end of the blog), even in Asia – it was detected in Japan in 2002 (eradicated) and 2020 (Shoda-Kagaya 2021). Put another way, 33 countries recorded outbreaks as of July 2021 (Porth 2021). About half of the 50 outbreaks have been eradicated; the remaining are under active management, including four of the largest populations in the U.S. (Trotter 2021)

A Canadian genetic study (Porth 2021) of five U.S. outbreaks (New York/New Jersey, Massachusetts, Illinois, and Ohio) and the two outbreaks in Toronto indicated two major sources of ALB: the North China plain and Korea (source of the Massachusetts populations). The second Toronto outbreak probably began with survivors of the first that escaped eradication. I note that shortly after the New York and Chicago outbreaks were detected, scientists said the most likely source was the northern plains of China, where China had planted large stands of poplars which quickly were attacked by ALB. These trees were made into crates and pallets to support to booming exports.

In Japan, ALB attacks elms, birches, and willows, not maples. Longer study will provide additional information about hosts (Shoda-Kagaya 2021).

A Swiss study (Augustinus 2021) confirms others’ finding that imports of stone are particularly likely to be associated with ALB-infested SWPM.

As I noted in an earlier blog, the latest U.S. outbreak in South Carolina presents several challenges. There are indications that the beetle completes its life cycle much faster in the subtropical climate – possibly within eight months (compared to two years in Massachusetts and Ohio). Also, APHIS is exploring new methods to destroy infested or vulnerable trees because workers can’t use heavy chipping equipment in swamps (Trotter 2021)

swamp in South Carolina where ALB is established; blue arrows indicate red maples photo by David Coyle

Emerald ash borer (EAB)

The EAB has been transported much less frequently in SWPM but once introduced it has proved much more difficult to eradicate or even contain. As a result it has caused much greater destruction. In North America, EAB is established in 35 states and five provinces. In the U.S. alone, an estimated 8.7 billion ash trees are under threat; this represents 2.5% of all U.S. aboveground biomass (de Andrade 2021).

In Europe, EAB is currently established in one province of Ukraine and 18 provinces of Russia. These include areas in St. Petersburg and in the Lower Volga basin that are separated from the core invasion range (Moscow) by 470 and 370 km, respectively. In Moscow EAB has caused mass mortality of European ash (F. excelsior); initial damage had been to the introduced North American species, green ash (Fraxinus pennsylvanica) (Volkovitsh, Bienkowski and Orlova-Bienkowskaja 2021).

In January 2021, USDA APHIS ended its 19-year domestic quarantine and regulation of movement of EAB-infested wood (e.g., firewood). Blogs objecting to this APHIS is now focused on applying classical biocontrol. As of September 2020, PPQ and its partners had released ~ 8 million parasitoid wasps in 350 counties in 30 states and Washington, DC (APHIS report; Duan 2021). APHIS reports successful recovery of wasp offspring in 22 states. The agency claims those recoveries demonstrate that the wasps are reproducing, becoming established in the areas where they were released, and most important, attacking and killing the beetles.

Duan (2021) says long-term study sites in Maryland, Michigan, Connecticut, Massachusetts and New York indicate that two of the four introduced biocontrol agents, the larval parasitoids Testrastichus planipennisi and Spathius galinae, have established co-existing populations via niche partitioning on different ash tree size classes. T. planipennis dominates on saplings and small ash trees while S. galinae predominates in pole- and sawtimber-sized trees. Duan says both parasitoids appear to have played a significant role in suppressing EAB populations, although he admits that it is too early to tell if we will see significant improvement in ash recovery and regeneration.

De Andrade (2021) has begun what he hopes will be a range-wide analysis of the impact of the biocontrol effort. He notes that Spathius galinae – although first releases began as recently as 2015 – is showing the best results, possibly because it does attack EAB larvae in larger trees. It will be some years before the efficacy of the program can be determined.

Sudden oak death (SOD)

In its FY2020 annual report (citation at end of blog), APHIS notes that the disease sudden oak death was confirmed as present in a 16th California county (Del Norte) that year. This detection thus connects quarantined areas from south of San Francisco to the one county in southwest Oregon (Curry County) where the disease is wreaking havoc.

The report notes that the causal pathogen, Phytophthora ramorum, can be moved through nursery stock. APHIS took its most important recent action regarding nursery transmission in FY2019, when it relaxed regulatory requirements. In May 2019 – during FY 2020 — a large “spill” of the pathogen on nursery stock from West Coast nurseries resulted in possibly infected plants being shipped to 18 states. The FY2020 report says nothing about this event. Instead, APHIS reports that in FY 2020, 25 nurseries participated in the interstate regulatory program and the agency released two from strict post-infection regulation. PPQ also supports annual surveys, with 23 states participating.

rhododendron seized in 2019 because it was infected by SOD; photo by Indiana Department of Natural Resources

In 2021 there was an even larger incident of infected plants being shipped to nurseries. We’ll see if APHIS includes this failure in next year’s Annual Report.

Asian gypsy moth (AGM)

The several species of Lymatria native to Asia are considered to pose a serious threat to North American forests. Tussock moths in East Asia have a much wider host range than the European Lymantria dispar dispar established in eastern North America. In many cases, the females fly – a behavior which would undermine the control measures applied in the East. Finally, beginning in the early 1990s, new trade patterns created opportunities for these moths to reach North America.

Several leaders of the U.S. and Canadian efforts to prevent their establishment have just published a fascinating history of how the prevention program targetting East Asian tussock moths was adopted (Mastro et al. 2021). The history notes that the first detections of AGM in the Pacific Northwest and British Columbia in the early 1990s posed several challenges to the phytosanitary agencies. These challenges were:

  1. how to justify under international trade rules regulating insects belonging to what was then thought  to be the broad species Lymatria dispar. That species had been established (ever more widely) in eastern North America since 1869. While this crisis arose before adoption of the World Trade Organization, its Agreement on the Application of Sanitary and Phytosanitary Standards, and the new language of the International Plant Protection Organization, the U.S. negotiating position was that it should be “against the rules” to regulate new introductions of established pests. For a thorough discussion of these issues, go to Fading Forests II.
  2. how to manage introductions via ships rather than the plant-origin commodities that they usually regulate.

The threat prodded the agencies to overcome these obstacles – a welcome exercise of initiative! Within a few years, APHIS and its Canadian counterpart (Canadian Food Inspection Service) developed a multi-layered monitoring and inspection program that was applied first to Russia and later to Japan, Korea, and China. Adoption of regulations was assisted by a simultaneous determination by scientists that the tussock moths of Asia actually belong to several species, including but not limited to L. dispar asiatica and L. dispar japonica. I blogged about recent successes and failures of this program and about a recent analysis of additional related species that also should probably be regulated.

Asian gypsy moths on a ship in Nakhodka harbor; USDA photo

Mastro et al. (2021) report that AGM incursions in the U.S. have been discovered on 62 occasions between 1991 and 2019. These have resulted in expensive projects which have – so far – prevented establishment of AGM. These efforts are expensive for both APHIS and the states. APHIS has also funded intensive surveillance efforts, including under the Plant Pest and Disease Management and Disaster Prevention Program (Section 7721). In Fiscal Years 2018 through 2020, APHIS funded surveillance of “Asian defoliators” at more than $1 million each year.

APHIS ANNUAL REPORT FOR FY2020

In its most recent annual report (Helping U.S. Agriculture Thrive— Across the Country and Around the World Plant Protection and Quarantine: Fiscal Year 2020), APHIS provides some of the data on pests cited above. In addition, it reports the number of inspections conducted; pests intercepted and identified; and other agency activities.

Notably, APHIS claims credit for negotiating the agricultural components of the U.S.-China Phase One Economic and Trade Agreement (adopted in May 2020). APHIS says this agreement was the culmination of 20 years effort — and helped open the Chinese market to almost $1 billion annually in sales of U.S. agricultural commodities. When the agreement was announced, I blogged about my frustration that APHIS did not use take this opportunity to press the Chinese to ensure that their wood packaging is pest-free. Chinese wood packaging violates U.S. import rules more often than any other country and U.S. forests need not pay the price. [or something like that.]

As I noted above, the APHIS report makes no mention of the huge “spill” of the sudden oak death pathogen through the nursery trade in 2019 (FY2020). How can APHIS justify this omission? 

SOURCES

Augustinus, B. Optimizing surveillance for priority and other quarantine forest pests in Switzerland. IUFRO Prague September 20 – 24, 2021

De Andrade, R. Emerald Ash Borer biocontrol in US IUFRO Prague September 20 – 24, 2021/

Duan, J. USDA Agriculture Research Service, Newark, DE in USDA document substituting for the 2022 USDA Forest Pest conference (“Annapolis”)”

Mastro, V.C., A.S. Munson, B. Wang, T. Freyman, & L.M. Humble. 2021. History of the Asian Lymantria species Program: A Unique Pathway Risk Mitigation Strategy. Journal of Integrated Pest Management, (2021) 12(1): 31; 1–10

Porth, Ilga. Universite Laval. Next-generation-sequencing-based biosurveillance for Anoplophora glabripennis IUFRO Prague September 20 – 24, 2021

Shoda-Kagaya, E. Current status of three invasive cerambycid pests in Japan. IUFRO Prague September 20 – 24, 2021

Trotter, R.T. USDA Forest Service, Hamden, CT in USDA document substituting for the 2022 USDA Forest Pest conference (“Annapolis”)

USDA APHIS PPQ Annual Report FY2020 Helping U.S. Ag Thrive— Across the Country and Around the World. Plant Protection and Quarantine: Fiscal Year 2020

Volkovitsh, M.G.; Bienkowski, A.O.; Orlova-Bienkowskaja, M.J. 2021. Emerald Ash Borer Approaches the Borders of the European Union and Kazakhstan and Is Confirmed to Infest European Ash. Forests

2021, 12, 691. https:// doi.org/10.3390/f12060691

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

“Global Tree Assessment”: #s at Risk, Threats, & Carbon Sequestration Planting

Kew Gardens U.K., home to Botanic Gardens Conservation International; Wikipedia

A massive international effort has completed a “Global Tree Assessment: State of Earth’s Trees”. This is the result of five years’ effort; it aims at a comprehensive assessment of the conservation status of all the Earth’s trees. As a result of their work, the authors issue a call to action and include specific recommendations. 

The leads were the Botanic Gardens Conservation International (BGCI) and International Union for Conservation of Nature’s (IUCN) Species Survival Commission (SSC) Global Tree Specialist Group. They were assisted by about 60 cooperating institutions and more than 500 individual experts. The Morton Arboretum was a major U.S. contributor. Here, my focus is on the global assessment. An accompanying blog contains my analysis of reports on the Morton Arboretum report for the U.S.

The Global Tree Assessment is the largest initiative in the history of the IUCN Red List process.  (This process is described in Box 3 of the report, on p. 12; and on p. 40.) As of the end of 2020, IUCN Red List assessments evaluated 28,463 tree species, representing half of all known tree species. Organizers hope to complete comprehensive conservation assessments of all tree species for inclusion on the IUCN Red List by 2023. Other sources utilized included draft Red List profiles and national-level assessments of those species that are found in only one country.

SUMMARY OF FINDINGS

Using these sources, the Global Tree Assessment evaluated 58,497 tree species worldwide. The study determined that 30% are threatened with extinction. This number could change significantly if a large proportion of the 7,700 species (13.2%) recorded as “Data Deficient” turn out to be at risk. At least 142 species are recorded as already extinct in the wild. Two-fifths (41.5%) are considered to be not at risk. Detailed species’ evaluations are provided at GlobalTreeSearch or GlobalTree Portal.

Brazilian forest converted to cattle pasture

The principal threats to trees globally are forest clearance and other forms of habitat loss (at least 65% of species) and direct exploitation for timber and other products (27% or more). The spread of non-native pests is said to affect 5% of the species. Climate change is having a measurable impact on 4% of the species and is expected to increase. (The situation in the United States differs significantly. Overexploitation plays almost no role and on-going habitat loss is important for only a few of the at-risk species.)

The authors decry the lack of attention, historically, to tree endangerment given trees’ ecological, cultural and economic importance. They hope that increased attention to the biodiversity crisis — an estimated 1 million animal and plant species threatened with extinction — and trees’ importance as carbon sinks will lead to increased conservation of trees and forests.  They warn, however, that tree-planting programs must put the right species in the right place, including utilizing species that are under threat. In other words, tree planting practices need to change. They note that a community of botanists and conservationists is ready to assist.

Centers of tree species diversity – and of species under threat – are in Central and South America, followed by the other tropical regions of Southeast Asia and Africa. Fifty-eight percent of tree species are single country endemics. The highest proportion of endemism is found in New Zealand, Madagascar and New Caledonia. The region with the highest proportion of native tree species under threat is tropical Africa, especially Madagascar. The highest numbers of species “Not Evaluated” or “Data Deficient” are in IndoMalaya (tropical Asia) and Oceania. In those regions, about a third of species fall in one of those categories.

forest in Central America

The assessment authors fear ecosystem collapse caused by major, large-scale disturbance events. Examples are recent unprecedented fires in California, southern Australia, Indonesia, and the Amazon (although they don’t mention Siberia). They also note mass mortality events over large areas of forest caused by other factors, including drought and heat stress and the increased incidence of pests. These events have led to a worrying decline of dominant tree species currently evaluated as “Least Concern.” Citing a 2010 report, they list as examples spruce in Alaska, lodgepole pine in British Columbia, aspen in Saskatchewan and Alberta, and Colorado pinon pine (Pinus edulis) in the American southwest.

The authors emphasize the importance of preventing extinction of monotypic tree families. Such events would represent a disproportionate loss of unique evolutionary history, biological diversity, and potential for future evolution. Of the 257 plant families that include trees, 12 are monotypic. They are scattered around the tropics and former Gondwanaland; none is found in the Neo- or Paleoarctic regions. While extinctions to date have rarely affected plants above the rank of genus, the global assessment authors worry that the on-going sixth extinction wave might result in extinctions at the genus or family level.

In this context, the assessment made a particular effort to evaluate the status of species representing the survival of Gondwanian Rainforest lineages. They found that 29% of these tree species are threatened with extinction. Two case studies focus on Australia. They mention habitat conversion but not two non-native pathogens widespread in Australia, Phytophthora cinnamomi and Austropuccinia psidii.  

formerly common, now endangered, Australian tree Rhodamnia rubescens, infected by Austropuccinia psidii; photo courtesy of Flickr

The proportion of total tree diversity designated as threatened is highest on island nations, e.g., 69% of the trees on St. Helena, 59% of the trees on Madagascar, 57% of the trees on Mauritius. Hawai`i is not treated separately from the United States as a whole. According to Megan Barstow of BGCI (pers. comm.), the just updated IUCN Red List includes 214 threatened tree species in Hawai`i.

[For the U.S. overall, the IUCN reports 1,424 tree species, of which 342 (24%) are considered threatened. In the companion U.S. assessment, the Morton Arboretum and collaborators found that 11% of 841 continental U.S. tree species are threatened.]

MAIN THREATS TO TREES

Habitat loss

Over the past 300 years, global forest area has decreased by about 40%. Conversion of land for crops and pasture continues to threaten more tree species than any other known threat. Additional losses are caused by conversion for urban and industrial development and transport corridors, and by changes in fire regimes. In total, these factors cumulatively threaten 78% of all tree species, 84% if one includes conversion to wood plantations.

Caribbean mahogany (Swietenia mahogani); photo by Miguel Vieria

Forest Exploitation

Exploitation, especially for timber, is the second greatest threat globally, affecting 27% of tree species (more than 7,400 tree species). The report focuses on centuries of harvest of valuable tropical timbers and exploitation for fuelwood, with an emphasis on Madagascar, where nearly half of all tree species (117 out of 244 tree species) are threatened.

Pests and diseases

Tree species are impacted by a wide range of pests and diseases that are spread by natural and artificial causes. Invasive and other problematic species are recorded as threats for 1,356 tree species (5%) recorded on the IUCN Red List. This figure might be low because some of the information is outdated (see my discussion of American beech in the companion blog about the North American report, here.)  Also, climate change is altering the survival opportunities for many pests and diseases in new environments. The example given is the ash genus (Fraxinus), under attack by not only the emerald ash borer in North America and now Russia and Eastern Europe but also the disease Ash Dieback across Europe.  The report refers readers to the International Plant Sentinel Network for early warning system of new and emerging pest and pathogen risks, as well as help in coordinating responses.

black ash (Fraxinus nigra) swamp; Flickr

Climate Change

Climate change is impacting all forest ecosystems and is emerging as a significant recorded threat to individual tree species. In the IUCN Red List assessments, climate change and severe weather is recorded as a threat in 1,080 (4%) cases. Trees of coastal, boreal and montane ecosystems are disproportionately impacted. The authors note that the actual impact of climate change is probably more widespread, as it is also impacting fire regimes and the survival, spread, and virulence of pests.

CURRENT CONSERVATION EFFORTS

In Protected areas

Currently, 15.4% of the global terrestrial surface has formal protection status. The IUCN study authors recognize in situ conservation of trees through protection of existing natural habitats as the best method for conserving tree diversity. It is therefore encouraging that at least 64% of all tree species are included in at least one protected area. However, representation is higher for species that are not threatened – 85% are represented in a conservation area while only 56% of threatened trees species are. Nor does the report assess the effectiveness of protection afforded by the various in situ sites. The authors express hope that the parallel IUCN Red List of Ecosystems will contribute to understanding of the efficacy of conservation efforts targetting forests.

The Global Trees Campaign is a joint initiative of Fauna & Flora International (FFI) and BGCI. Since 1999 the campaign has worked to conserve more than 400 threatened tree species in more than 50 countries. The current focus is on six priority taxa = Acer, Dipterocarps, Magnolia, Nothofagus, Oak, and Rhododendron.

Rhododendron in Cook Forest State Park, PA; photo by F.T. Campbell

In Botanic gardens and seed banks

Especially for species under threat, conservation outside their native habitat – ex situ conservation – is an essential additional component. Currently 30% of tree species are recorded as present in at least one botanic garden or seed bank. Again, representation is higher for species that are not threatened – 45% are represented compared to only 21% of threatened tree species. For 41 species, ex situ conservation provides the only hope of survival, since they are extinct in the wild.

AN URGENT CALL FOR ACTION

The authors and collaborators who prepared the Global Tree Assessment hope that this report will help prompt action and better coordination of priorities and resources to better ensure that all tree species are supported by in situ conservation sites and by appropriate management plans. They state several times the importance of restoration plantings relying on native species. The purpose of plantings needs to include conservation of biological diversity, not just accumulation of carbon credits. The Ecological Restoration Alliance of Botanic Gardens (https://www.erabg.org/) is demonstrating that forest restoration can benefit biodiversity conservation. In many cases, propagation methods need to be developed. Also, projects must include aftercare and monitoring to ensure the survival of planted seedlings.

The IUCN assessment notes that ex situ conservation is an important backup. Education, capacity-building and awareness-raising are needed to equip, support, and empower local communities and other partners with the knowledge and skills to help conserve threatened trees.

Policy

The report say it does not address policy and legislation – a gap that fortunately is not quite true. The report both summarizes pertinent international agreements but also provides specific recommendations.

The international agreements that pertain to tree and forest conservation include:

  • Convention on Biological Diversity (CBD) and several specific programs: the Forestry Programme, Protected Area Programme and Sustainable Use Programme.
  • Global Strategy for Plant Conservation (GSPC), which is now developing post-2020 targets.
  • United Nations Framework Convention on Climate Change (UNFCCC) and countries’ implementing pledges to conserve carbon sinks, e.g., REDD+ (Reducing Emissions from Deforestation and Forest Degradation)
  • United Nations Strategic Plan for Forests 2017-2030
  • Global Plan of Action for the Conservation and Sustainable Use of Forest Genetic Resources
  • Convention on International Trade in Endangered Species, which currently protects 560 tree species, including 308 of the most threatened timbers

The report also mentions the voluntary New York Declaration on Forests, under which more than 200 entities – including governments, businesses, and Indigenous communities — have committed to eliminating deforestation from their supply chains. The supply chains touched on include those for major agricultural commodities, production of which is one of the greatest threat to trees.

SPECIFIC RECOMMENDATIONS

1. Strengthen tree conservation action globally through the formation of a new coalition that brings together existing resources and expertise, and applies lessons from the Global Trees Campaign to radically scale up tree conservation.

2. Use information in the GlobalTree Portal on the conservation status of individual tree species and current conservation action to plan additional action at local, national, and international levels, and for priority taxonomic groups. Build on the Portal by strengthening research on “Data Deficient” tree species, and collating additional information threatened species to avoid duplication of efforts and ensure conservation action is directed where it is needed most.

3. Ensure effective conservation of threatened trees within the protected area network by strengthening local knowledge, monitoring populations of threatened species and, where necessary, increasing enforcement of controls on illegal or non-sustainable harvesting of valuable species. Extend protected area coverage for threatened tree species and species assemblages that are currently not well-represented in protected areas.

4. Ensure that all globally threatened tree species are conserved in well-managed and genetically representative ex situ living and seed bank collections, with associated education and restoration programs.

5. Align work with the UN Decade on Ecosystem Restoration 2021–2030, engaging local communities, government forestry agencies, the business community, and other interested parties to ensure that the most appropriate tree species, including those that are threatened, are used in tree planting and restoration programs.

6. Improve data collection for national inventory and monitoring systems and use this information to reduce deforestation in areas of high tree diversity in association with REDD+ and Nationally Determined Contributions (NDCs).

7. Increase the availability of government, private and corporate funding for threatened tree species, and ensure that funding is directed to species and sites that are in greatest need of conservation.

SOURCE

Global Tree Assessment State of Earth’s Trees September 2021 Botanic Gardens Conservation International available here

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

The Morton Arboretum Assesses U.S. Tree Genera at Risk

 

habitat of the Florida torreya tree; photo via Creative Commons

In August, the Morton Arboretum announced completion of a series of reports on the conservation status of major tree genera native to the continental United States. It is available here.  The series of reports provides individual studies on Carya, Fagus, Gymnocladus, Juglans, Pinus, Taxus, and selected Lauraceae (Lindera, Persea, Sassafras). (Links to the individual reports are provided at the principal link above.)  

The project was funded by the USDA Forest Service and the Institute of Museum and Library Services, The Morton Arboretum and Botanic Gardens Conservation International U.S.

Each report provides a summary of the ecology, distribution, and threats to species in the genus, plus levels of ex situ conservation efforts. The authors hope that the data in these reports will aid in setting conservation priorities and coordinating activities among stakeholders. The aim is to further conservation of U.S. keystone trees.

These reports are part of the overall “Global Tree Assessment: State of Earth’s Trees”  compiled under the auspices of Botanic Gardens Conservation International (BGCI) and IUCN SSC Global Tree Specialist Group. I discuss the global assessment in a separate blog to which I will link. The global report evaluates species’ status according to both the International Union of Conservation of Nature’s (IUCN) Red List and NatureServe. The process used is explained in each both the international and U.S. reports. For the U.S. overall, the global assessment identifies 1,424 species of tree, of which 342 (24%) are considered threatened. Hawai`i specifically is home to 241 endangered tree species (Megan Barstow, BGCI Conservation Officer, pers. comm.). See my blogs about threats to Hawaiian trees.

Quercus lobata (valley oak) at Jack London State Park, California

Like the global assessment, these individual studies of nine genera–carried out by the Morton Arboretum–are a monumental accomplishment. They vary in size and format. The report on oaks was completed first and is the most comprehensive. It is 220 pages, incorporating individual reports on 28 species of concern. The report on pines is 40 pages. It contains summary information and tables on all 37 pine species native to the United States, but lacks write-ups on individual species. The report on Lauracae is 25 pages; it evaluates the threat to five species in three genera from laurel wilt disease. The report on walnuts is 23 pages. It includes brief descriptions of six individual species, including butternut. The report on hickories (Carya spp.) is 20 pages.  It provides brief description of 11 species. The report on yews is 18 pages. It covers three species. The report on Fagus addresses the single species in the genus, American beech. It is 17 pages. The shortest report is on another single species, Kentucky coffeetree; it is 15 pages.

Coverage of Threats from Non-Native Insects and Diseases in the Morton Arboretum Reports

In keeping with my focus, I concentrated my review of these nine reports on their handling of threats from non-native insects and pathogens. Six of the reports make some reference to pests – although the discussion is not always adequate, in my view. There are puzzling failures to mention some pathogens.

Genera subject to minimal threats from pests (native or non-native) include the monotypic Kentucky coffeetree (Gymnocladus dioicus), whichis considered by the IUCN to be Vulnerable due habitat fragmentation, rarity on the landscape, and population decline.

A second such genus is Carya spp., the hickories. The entire genus is assessed by the IUCN as of Least Concern. The Morton study ranked two species, C. floridana and C. myristiciformis, as of conservation concern. 

Three evaluators – the IUCN, the Morton Arboretum, and Potter et al. (2019) – agree that one of the three U.S. yew species, Florida torreya (Taxus floridana or Torreya taxifolia), is Critically Endangered because of its extremely small range, low population, and deer predation. Indeed, Potter et al. (2019) ranked Florida torreya as first priority of all forest trees in the continental United States for conservation efforts. However, the Morton Arboretum analysis makes no mention of the canker disease reported by, among others, the U.S. Forest Service.

A third of the 28 oak (Quercus spp.) species considered to be of conservation concern per the Morton study criteria are reported to be threatened by non-native pests. Pest threats to oak species not considered to be of conservation concerned were not evaluated in the report.

The Morton report records 37 pine species (Pinus spp.) as native to the U.S. Native and introduced insects and pathogens are a threat to many, especially in the West.

Two reports – those on the Lauraceae and beech – focus almost exclusively on threats from non-native pests. The report on walnuts (Juglans spp.) divides its attention between non-native pests and habitat conversion issues. This approach comes into some question as a result of the recent decision by state plant health officials to that thousand cankers disease does not threaten black walnut (J. nigra) in its native range.

black walnut (J. nigra) photo by F.T. Campbell

Here I examine five of the individual genus reports in greater detail.

Oaks

The Morton report says that more than 200 oak species are known across North America, of which 91 are native in the United States. The study concludes that 28 of these native oaks are of conservation concern based on extinction risk, vulnerability to climate change, and low representation in ex situ collections. [The IUCN Red List recognizes 16 U.S. oak species as globally threatened with extinction.] Nearly all of the Morton’s report 28 species are confined to small ranges. In the U.S., regional conservation hotspots are in coastal southern California, including the Channel Islands; southwest Texas; and the southeastern states.

The summary opening section of the Morton report says 10 (36%) of the threatened oaks face a threat by a non-native pathogen. It admits that lack of information probably results in an underestimation of the pest risk. I found it difficult to confirm this overall figure by studying the detailed species reports because in some cases the threatening pathogen is not currently extant near the specific tree species’ habitat. I appreciate the evaluators’ concern about the potential for the pathogen, e.g., Phytophthora ramorum or oak wilt, to spread from its current range to vulnerable species growing on the other side of the continent. However, I wish the overview summary at the beginning of the report were clearer as to which species are currently being infected, which face a potential threat.

The report emphasizes the sudden oak death pathogen (SOD; Phytophthora ramorum), stating that it which currently poses a significant risk to wild populations of Q. parvula. However, the situation is more complex. As I note in my blog on threats to oaks, Q. parvula is divided into two subspecies. In the view of California officials, one, Q. p. var. shrevei, is currently threatened by SOD but the other, Q. p. var. parvula, (Santa Cruz Island oak) is currently outside the area infested by the pathogen. Perhaps the Morton Arboretum evaluators consider the potential risk to the second subspecies to be sufficient to justify stating that the pathogen poses a significant threat to the entire species; but I would appreciate greater clarity on this matter.

The report also mentions the potential threat to several rare oak species in the Southeast if SOD spreads there. While the Morton report rarely discusses species that have not been assessed as under threat, it does note that two species ranked as being of Least concern – coast live oak (Q. agrifolia) and California black oak (Q. kelloggii) – have been highly affected by SOD. 

The Fusarium disease vectored by the polyphagous and Kuroshio shot hole borers is mentioned as a threat to Engelmann (Q. engelmannii)and valley (Q. lobata) oaks. The latter, in particular, is considered by the Morton Arboretum assessors to be already much diminished by habitat conversion. 

In the East, hydrological changes have facilitated serious damage to Ogelthorpe oak (Q. oglethorpensis) by the fungus that causes chestnut blight–Cryphonectria parasitica. 

The Morton study mentions oak wilt (Ceratocystis or Bretziella fagacearum) as an actual or potential factor in decline of oaks in the red oak clade (Sect. Lobatae). Only one of the oak species discussed – Q. arkansana – is in the East, were oak wilt is established. The rest are red oaks in California, where oak wilt is not yet established. Again, there is no discussion of the impact of oak wilt on widespread species not now considered to be of conservation concern.

In the individual species profiles making up the bulk of the Morton report on oaks, but not in the summary, the Morton report also mentions the goldspotted oak borer (Agrilus auroguttatus) as an actual or potential factor in decline of the same oaks in the red oak group. The following species – Q. engelmanni, Q. agrifolia, Q. parvula, Q. pumila — are in California and at most immediate threat.

The Morton study also mentions several native insects that are attacking oaks, and oak decline. It calls for further research to determine their impacts on oak species of concern.

For analyses of the various pests’ impacts on oaks broadly, not focused on at-risk tree species, see my recent blog updating threats to oaks, posted here, and the pest profiles posted at www.dontmovefirewood.org

Pines

The Morton report lists 12 pine species as priorities out of the total of 37 species native to the United States. The report notes that the majority of the at-risk species in the West are threatened primarily by high mortality from one or more pests, in particular native bark beetles.

 Six of the 12 priority species are five-needle pines affected by white pine blister rust (WPBR; Cronartium ribicola). The report contains maps showing the distribution of WPBR. In some cases, the native mountain pine beetle (Dendroctonus ponderosae) contributes to immediate mortality. Presentation of recommendations is scattered and sometimes seems contradictory. Thus, P. longaeva (bristlecone pine) is said by the IUCN to be stable and is not listed among the 12 threatened species, but the Morton Arboretum assessors called for its receiving high conservation priority. P. albicaulis (whitebark pine) is a candidate for listing as Threatened under the Endangered Species Act, but the Morton Arboretum authors did not single it out for priority action beyond listing it among the dozen at-risk species.

P. albicaulis (whitebark pine) at Crater Lake National Park; photo courtesy of Richard Sniezko, USFS

The report also notes impacts by Phytopthora cinnamomi on pines; a maps shows the distribution of this non-native pathogen. A third non-native pathogen — pitch canker (Fusarium circinatum) — is mentioned as affecting Monterrey pine (P. radiata). Torrey pine (Pinus torreyana) is also affected by pitch canker, but this pathogen is ranked by the Morton study as causing only moderate mortality in association with other factors. Torrey pine is ranked as critically endangered and decreasing in populations.

The report also publishes the rankings developed by Potter et al. (2019).  P. torreyana was the top-ranked pine, ranked at 18 (less urgent than, eastern hemlock).

The Morton study authors concluded that native U.S. pines are under serious threat. However, their economic, ecological, and cultural importance makes them obvious targets for continued conservation priority.

For my analysis of the various pests’ impacts on pines broadly, see the pest profiles posted at www.dontmovefirewood.org

Lauraecae

The Morton group analyzed five of the 13 species native to the United States, chosen based on three factors – tree-like habit, susceptibility to laurel wilt disease, and distribution in areas currently affected by the disease. They note the importance of Sassafras as a monotypic genus.

Horton House before death of the redbay trees; photo by F.T. Campbell

The Morton study notes the conservation status of several species needs changing due to the rapid spread of laurel wilt disease. I applaud this willingness to adjust, although I would be inclined to assign a higher ranking based on the most recent data from Olatinwo et al. (2021), cited here.

  • Redbay (Persea borbonia) was assessed in 2018 as IUCN Least Concern; it is now being re-assessed, with a probable upgrade to Vulnerable. The Morton study says that recent evidence points towards the ecological extinction of P. borbonia from coastal forest ecosystems. Potter et al. (2019) ranked redbay as fifth most deserving of conservation effort overall.
  • Silk bay (Persea humilis), endemic to Florida, is currently being assessed for the IUCN; it is recommended that it be designated as Near Threatened.
  • Swamp bay (Persea palustris) is widespread. It is being assessed for the IUCN; it is recommended for the Vulnerable category.
  • Sassafras (Sassafras albidum) is widely distributed. Sassafras had been assessed as of Least Concern as recently as the 2020 edition of the IUCN Red List. The Morton study notes that the current distribution of laurel wilt disease spans only a small percent of its range, so it does not pose an imminent threat to sassafras. However, cold-tolerance tests for the disease’s vector indicate the possibility of northward spread into more of the sassafras’ distribution. I note that laurel wilt is currently present in northern Kentucky and Tennessee.  

American Beech  

The Morton report notes that beech (Fagus grandifolia) is very widespread and a dominant tree in forests throughout the Northeastern United States and Canada. It is the only species in the genus native to North America, so presumably of high conservation interest. The report also notes its ecological importance (see also Lovett et al. 2006).

Beech bark disease is reported by the Morton Arboretum to have devastated Northeastern populations. The disease is well established in all beech-dominated forests in the United States, though it occurs on less than 30% of American beech’s full distribution. After mature beech die, thickets of young, shade-tolerant root sprouts and seedlings grow up, preventing regeneration of other tree species. Nevertheless, American beech was listed as of Least Concern by the IUCN in 2017.

The report makes no mention of beech leaf disease, which came to attention after the Morton assessment project had been almost completed. I think this is a serious gap that undermines the assessment not just of the species’ status in the wild but also of the efficacy of conservation efforts.

healthy American beech; photo by F.T. Campbell

Walnuts

The Morton team evaluated five species of walnut (Juglans californica, J. hindsii, J. major, J. microcarpa, and J. nigra); and butternut (J. cinerea). Thousand cankers disease – caused by the fungus Geosmithia morbida, which is vectored by the walnut twig beetle (Pityophthorus juglandis) – is reported by the Morton team as second in importance to butternut canker. However, as I noted in a recent blog, the states that formerly considered the disease to pose a serious threat no longer think so and are terminating their quarantine regulations. This decision too recent for consideration by the Morton team.

One of the walnuts — Juglans californica (Southern Calif walnut) — is considered threatened by habitat loss. The rest of the walnuts are categorized by the IUCN as of Least Concern.

cankered butternut in New England; photo by F.T. Campbell

Butternut (Juglans cinerea), however, is considered by the IUCN to be Endangered. Although present across much of the Eastern deciduous forest, it is uncommon. It has suffered an estimated 80% population decline as a result of the disease caused by the butternut canker fungus Ophiognomonia clavigignenti-juglandacearum. 

SOURCES

Beckman, E., Meyer, A., Pivorunas, D., Hoban, S., & Westwood, M. (2021). Conservation Gap Analysis of Am beech. Lisle, IL: The Morton Arboretum. August 2021

Beckman, E., Meyer, A., Pivorunas, D., Hoban, S., & Westwood, M. (2021). Conservation Gap Analysis of Native U.S. Hickories. Lisle, IL: The Morton Arboretum.

Beckman, E., Meyer, A., Pivorunas, D., Hoban, S., & Westwood, M. (2021). Conservation Gap Analysis of Kentucky Coffeetree. Lisle, IL: The Morton Arboretum.

Beckman, E., Meyer, A., Denvir, A., Gill, D., Man, G., Pivorunas, D., Shaw, K., & Westwood, M. (2019). Conservation Gap Analysis of Native U.S. Oaks. Lisle, IL: The Morton Arboretum.

Beckman, E., Meyer, A., Pivorunas, D., Hoban, S., & Westwood, M. (2021). Conservation Gap Analysis of Native U.S. Pines. Lisle, IL: The Morton Arboretum.

Beckman, E., Meyer, A., Pivorunas, D., Hoban, S., & Westwood, M. (2021). Conservation Gap Analysis of Native U.S. Laurels. Lisle, IL: The Morton Arboretum. August 2021

Beckman, E., Meyer, A., Pivorunas, D., Hoban, S., & Westwood, M. (2021). Conservation Gap Analysis of Native U.S. Walnuts. Lisle, IL: The Morton Arboretum. August 2021

Beckman, E., Meyer, A., Pivorunas, D., Hoban, S., & Westwood, M. (2021). Conservation Gap Analysis of Native U.S. Yews. Lisle, IL: The Morton Arboretum.

Lovett, G.M., C.D. Canham, M.A. Arthur, K.C., Weathers, and R.D. Fitzhugh. 2006. Forest Ecosystem Responses to Exotic Pests and Pathogens in Eastern North America. BioScience Vol. 56 No. 5 May 2006)

Olatinwo, R.O., S.W. Fraedrich & A.E. Mayfield III. 2021. Laurel Wilt: Current and Potential Impacts and Possibilities for Prevention and Management. Forests 2021, 12, 181. 

Potter, K.M., M.E. Escanferla, R.M. Jetton, G. Man, B.S. Crane.  2019. Prioritizing the conservation needs of United States tree species: Evaluating vulnerability to forest insect and disease threats. Global Ecology and Conservation (2019), doi: https://doi.org/10.1016/

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

New report: Forest Disturbances in the West and their implications for sustainability

whitebark pine killed by white pine blister rust; Crater Lake National Park; photo by F.T. Campbell

Increasing frequency and severity of forest disturbances pose significant challenges to the sustainable management of forests in the West and to the goods and services they provide. A recent study (Barrett and Robertson 2021; full citation at end of blog) found that natural and human-caused disturbances affected 22.3% of forest land in the West over a 5-year period.  The study analyzed fire, drought, insects, disease, invasive plants, their interactions, and their socioeconomic impacts. Climate change was found to affect most disturbance processes now and is expected to continue to do so in the future.

The impacts of these disturbances varied; most disturbances did not result in stand-replacing mortality.

Overarching Findings on Disturbance Agents in Western Forests

  • Insect and disease outbreaks were the most extensive disturbance types. Each was estimated to affect 6.1 million hectares. Insect and disease outbreaks also caused the highest levels of tree mortality. This finding resulted from what was described as a relatively “low” threshold for “disturbance.” The authors set this threshold at disturbances that cause damage or mortality to 25% of trees in a stand or 50% of an individual tree species.

The overwhelmingly important causal agent was the mountain pine beetle (MPB; Dendroctonus ponderosae). Even after an approximately 50% drop in mortality after its peak years in the 2000s, MPB caused almost half the total area affected by all bark beetles combined  2000-2016.

The great majority of “pest” organisms causing disturbance in the West are native. Some non-native pests are important, though, and they are expected to become more important in the future. The most damaging non-native agent is white pine blister rust (WPBR; Cronaritum ribicola). Despite the largest control effort (in the 1930s), WPBR has caused drastic declines in white pines in the West. Currently attention focuses on high-elevation pines, especially whitebark pine (Pinus albicaulis), which is suffering extensive mortality from a combination of drought, MPB, and WPBR.

tanoak mortality in Big Sur, California; photo by Matteo Garbelotto

Other non-native pests discussed in the report are balsam woolly adelgid, larch casebearer, spruce aphid, and sudden oak death (SOD). The report notes the presence of a second strain of the causal agent of SOD (Phytophthora ramorum). In June 2021, a third strain was detected in Oregon forests (COMTF newsletter). There are mere mentions of goldspotted oak borer and polyphagous shot hole borer. The California fivespined ips (Ips paraconfusus) is reported to vector the fungus Fusarium circinatum which causes pitch canker disease in Monterey pine (Pinus radiata).

  • The second most extensive disturbance agent in the West is human activity – silvicultural management and conversion to non-forest land uses. These activities affected 4.4 million ha.
  • The third most extensive disturbance agent is grazing (primarily livestock). This affected 3.9 million ha.
  • Fire thus ranks fourth as a disturbance agent – as measured by extent. During a five-year period ending in 2017 or 2018, fire affected 3.7 million ha. (I don’t know whether this ranking will change in response to the fire cataclysms of the most recent years; apparently the latest year included in the data was 2017.) The area affected by fire during this period was double that of the period 1960 to 2000. However, fire frequency and extent were still considerably lower than in the 1920s through1940s, before the advent of fire suppression, especially in the drier forests of the interior West.
  • Other disturbance events – including those caused by weather and vegetation (presumably invasive plants) – affected far smaller areas: a total of 2.3 million ha.

Furthermore, drought and invasive plants – while increasing in extent & intensity – are often considered contributing factors rather than as proximate causes.

Data on past disturbance extents are poor for all these causes except fire. Analysis is further complicated by the high variability of disturbance events – year to year and across space. It is also often difficult to determine the ultimate causes. This makes the implications of these recent increases difficult to ascertain.

As the report points out, forest conditions are inherently dynamic, not stable. They note particularly human manipulation of fire – originally setting fires and then, more recently, suppressing them, has shaped the region’s forests for centuries. Fire suppression has significantly altered forest structure throughout the region, resulting in increasing fuel loads, decreasing resilience to fire and other disturbances.

Impacts of Climate Change

Fire suppression has also increased rates of carbon sequestration (see below).

The report notes that while past timber harvest, land clearing, insect outbreaks, and fires have reduced carbon stocks in forests across the United States to about half their maximum storage potential, recent vegetation and forest cover dynamics have resulted in net increases in carbon stocks in the West – despite CO2 emissions from trees killed by fire and insect damage since 2000.

In the future, climate change is expected to increase tree mortality substantially. In drier forests, mortality would result from increased fire incidence facilitated by a combination of longer fire season and decreased snowpack, reduced summer precipitation, and higher temperatures. In high-elevation and mesic forests, mortality would result from reduced snowpack, precipitation, and temperature.

About half of the West is likely to experience unprecedented climates by the end of this century. This change in climate could trigger changes in vegetation types and extent, net primary productivity, wildfire frequency, and expansion of the range of tree-damaging pests. Grasslands, chaparral, and montane forests are expected to expand; subalpine forests, tundra, and Great Basin woodlands are expected to contract. 

Except in Arizona, California, and New Mexico, bark beetles are having a larger impact on forest CO2 emissions than is fire. Future impacts are unclear. Under moderate climate conditions forests would grow faster than under more severe scenarios, but they would thereby generate more fuel for the fires likely to occur during dry years. These fires might ultimately lead to lower carbon stocks.

I have addressed the invasive plant data in a separate blog.

Reducing Impacts via Management

Barrett and Robertson (2021) suggest management actions that could reduce the impact of these disturbances. First, they mention actions aimed at reducing invasions by non-native insects, pathogens, and plants. Also, they name actions to ameliorate climate change, such as reducing greenhouse gas emissions or increasing carbon sequestration and storage to mitigate expected future damage from wildfire, drought, and beetles.

They recommended a series of on-the-ground management actions: fuel reduction treatments; thinning to reduce tree mortality from drought; favoring species that do not host specific pests; and planting genetically resistant varieties. They call for caution to prevent transport of pathogens to new areas during restoration planting of nursery stock or in “assisted migration” projects. Economic impacts of disturbance events on recreation could be mitigated by altering the timing and duration of recreational site visits. The authors also note that the best choices will differ both by site-specific factors and by management goals. They call for community education programs, cooperative stewardship across multiple agencies and landowners, and local and regional planning.

Details on Pest Impacts

Disease dominated in the high elevations of interior mountain ranges and in the precipitation-heavy regions of Oregon and Washington. Even in these locations, mortality levels are often low, resulting in multi-aged stands with complex structure. Patterns of disturbance are expected to change as pathogens and their hosts adapt to climate change. The microbes might evolve more rapidly than the host trees.

test planting of rust-resistant seedlings of whitebark pine at Crater Lake NP; photo by Richard Sniezko

Sudden oak death (SOD) is now the leading biotic cause of tree mortality in coastal forests of California [and possibly Oregon?]. In heavily infested areas SOD has caused conversion of previously tanoak-dominated stands. The report provides a summary of Oregon’s attempts to eradicate SOD from 2001 to 2012.

I am surprised by the failure to mention non-native pest impacts on two narrowly endemic species: Port-Orford cedar root disease and pitch canker disease in Monterrey pines – other than to mention the vector (above).

test planting of disease-resistant Port-Orford cedar; photo by Richard Sniezko

Insect outbreaks were most common in pine forests. Decades of fire suppression, and now climate change, have substantially altered forest conditions over millions of hectares, primarily increasing the density of shade-tolerant and fire-intolerant trees (e.g., true firs, Abies spp.). Balsam woolly adelgid (BWA; Adelges piceae) is now threatening subalpine fir stands in British Columbia, Oregon, Washington, Idaho, Montana, and Utah. BWA is ranked as the 10th most damaging forest insect, first among non-native species over the next few decades (2013-2027). The spruce aphid (Elatobium abietinum) is having its most significant impact in coastal Southeast Alaska on Sitka spruce and in Arizona on Engelmann spruce. Projected increases in temperature and the frequency of droughts in the West will likely make spruce aphid a more significant disturbance agent in coming decades.

risk map for goldspotted oak borer

In discussing the goldspotted oak borer (GSOB; Agrilus coxalis sic) in California and emerald ash borer (EAB; Agrilus planipennis) in Colorado, Barrett and Robertson (2021) say that the heterogeneity of western landscapes provides some buffer against invasion.  However, I note that GSOB threatens oaks throughout California (see the map at left). EAB threatens riparian areas of the Pacific states (see map below). These riparian areas are admittedly small in geographic extent but ecologically vital.

Barrett and Robertson (2021) expect seven tree species to suffer substantial levels of tree mortality in the near future.  Six are pines threatened in large part by mountain pine beetle, led by the two high-elevation five-needle pines, whitebark pine (58% of total basal area) and limber pine (44%). These are followed by lodgepole pine (39%), ponderosa pine (28%), pinyon pine (27%), Jeffrey pine (26%). The seventh is grand fir (25% of total basal area); the report does not specify which agents are responsible.

Data Issues

The report notes that insects and pathogens are only partially covered by existing monitoring programs. Pathogens are particularly hard to detect and to make conclusive attributions of causality.

SOURCE

Barrett, T.M. and G.C. Robertson, Editors. 2021. Disturbance and Sustainability in Forests of the Western United States. USDA Forest Service Pacific Northwest Research Station. General Technical Report PNW-GTR-992. March 2021

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

Tuning in to the News – Mostly Depressing

In late July I participated in the annual meeting of the National Plant Board (NPB) – the organization representing the states’ phytosanitary agencies. USDA’s APHIS, DHS’ Bureau of Customs and Border Protection (CBP), and various industry associations also participated in the meeting. As usual, I learned lots of depressing developments.

A. Old problems continue to vex:

rhododendron plant infested by P. ramorum; photo by Jennifer Parke, Oregon State University

1) Sudden Oak Death in the Nursery Trade – Again!!!

As you might remember, spring 2019 saw an alarming number of plants infested by the sudden oak death pathogen (Phytophthora ramorum) shipped from west coast nurseries to nurseries in 18 states. Another major incident occurred in 2021. The California Oak Mortality Task Force (COMTF) newsletter for June 2021 reports that one nursery in Oregon shipped plants exposed to P. ramorum to big-box stores in 36 states — twice the number of states that received pathogen-exposed plants in 2019.

The first such incident was in 2004 – 17 years ago! Officials of the states that receive these infested plants are angry that every few years they must divert their resources from other duties to inspect nurseries in their states that have been exposed to the pathogen. They note that these “trace-forward” projects cost state governments money and prevent their carrying out other duties; they also impose significant costs on the in-state nurseries due to holds on sales. When infested plants are found, all these costs rise substantially.

The plant health official from Alabama noted that a single west coast nursery that had repeatedly been found to have infected plants shipped 29 lots of host plants to her state in spring 2021. As is clear from the COMTF article, other states also received thousands of plants that had been exposed to the pathogen. The Alabama official questioned why APHIS tilts so far toward a regulatory system that makes it possible for the “exporting” nurseries to ship. The result – too often – is that an infection at one small business can (repeatedly) impose high costs on hundreds of receiving nurseries and states. [I wonder whether anyone has considered a lawsuit against the source nurseries claiming damages? Would that be successful if the regulatory agencies approved the shipments because – at that time – their inspections had failed to detect the problem?]

Officials from the three west coast states, however, want to support their own nurseries’ efforts to relax regulations and maintain or open markets in the central and eastern states. They point to their own considerable efforts to inspect and certify the pest-free status of nurseries in their states.

Because of the different points of view among the states, the National Plant Board per se has never taken a position on the issue.

However, many states – and even APHIS Deputy Administrator El-Lissy – agree that something is not working. So APHIS is in the midst of reviewing its program, with input from NPB members. Such program reviews have been undertaken several times over the past 18 years. So far, they have never produced a program that effectively stops sales of pathogen-infested plants.

2) Contaminated Wood Packaging

Kevin Harriger of CBP reported that over the nine-month period October 2020 – June 2021, CBP intercepted 1,563 shipments that were in violation of ISPM#15, the international rule that requires that wood packaging be treated to kill pests. Most, or 1,148 shipments (73%), lacked the required mark certifying treatment. Four hundred fifteen (26%) of the total number of shipments had a live pest present. Nearly three quarters of the non-compliant shipments transported miscellaneous cargo. This is not a surprise: all of these characteristics are in keeping with past experience.

Meanwhile, APHIS Deputy Director El-Lissy said APHIS was working with importers, exporting countries’ departments of agriculture, and others to improve compliance. Apparently there were two high-profile incidents when shipments of car components were rejected because of ISPM#15 issues. I am trying to learn more about these incidents.

I recently blogged about the pest risk associated with incoming shipping containers and dunnage.  

3) Asian Gypsy Moths (Tussock moths) Still Infesting Ships

Harriger also said that the period 2019-2020 saw the largest number of ships infested by Asian tussock moth eggs since the program began in 2012.  [I am aware that the Entomological Society is searching for a new name for this group of insects.] On average, 12 of 100 approaching vessels was infested. CBP is using sophisticated models to identify regions within Asian ports where conditions exacerbate the risk of moth contamination. CBP can match individual ships’ loading records to this information to pinpoint which are most likely to be infested.

Oregon and Washington continue to find both Asian and European tussock moths in traps along the Columbia River. Such detections prompt eradication programs of varying expense and disruption.

[In April, I blogged about a report evaluating the risk posed by several Asian tussock moths; the report was prepared by experts under the auspices of the North American Plant Protection Organization.]

B. In addition to the arrival of new pests, there is an alarming spread of established ones:

1) Beech leaf disease

State phytosanitary officials reported detections of beech leaf disease (BLD) in Maine and Virginia. The devastating impact of BLD on this hard mast tree species is described here. BLD has now spread through much of southern New England (Connecticut, Rhode Island, Massachusetts) and up the coast to Maine. Connecticut reports that trees of all sizes are affected. Maine reports that the disease is widespread in the central coastal region.

beech trees in Prince William Forest Park

Virginia reported that the disease has been detected in Prince William Forest Park, a forested area south of Washington, D.C., managed by the National Park Service. This detection is too recent to say how widespread it is.

2) Laurel wilt

Kentucky’s plant health officer reported that laurel wilt disease has been detected on sassafras trees in Louisville, at the northern tip of the state and across the river from Ohio. He noted that a second host plant, spice bush, is in the nursery trade. While laurel wilt is not regulated, officials are concerned about its impact in natural forests. Neighboring states are concerned.

sassafras in northern Virginia; photo by F.T. Campbell

I learned by looking at the map that laurel wilt has also been detected in Sullivan County, Tennessee, on the Virginia border.

3) Spotted Lanternfly

This pest of grapes, tree fruits, and a wide variety of native trees is spreading in Pennsylvania, Delaware, New Jersey, and Maryland. It has also been found in Ithaca, NY, and in Connecticut. The populations in Virginia and West Virginia also continue to spread; a disjunct outbreak has been detected in Prince William County, VA. (south of D.C.). Most alarming are disjunct populations in Ohio on the West Virginia border and in Indiana on the Ohio River border with northern Kentucky. See map here.

The Indiana population has been present for several years. The affected woodland is close to RV parks and other facilities that make further spread likely.

California has established an external quarantine targetting the spotted lanternfly .

C. Wrestling with Continuing Issues:

1) States try to compensate for APHIS’ end of regulating the emerald ash borer and firewood

The members of the NPB have spent years discussing the pros and cons of continuing to regulate ash wood to contain the emerald ash borer (EAB). As I blogged earlier, APHIS has ended its regulatory program. One state – Minnesota – is seeking to use an APHIS procedure to get APHIS’ continued protection from importation of EAB-infested wood (presumably from Canada). Under the Federally Recognized State Managed Phytosanitary Program (FRSMP), a state petitions APHIS to recognize its program for a specific pest. If APHIS grants that recognition, the agency will support the state by continuing to regulate imports of that pest or commodities that might transport the pest when they are destined for the regulating state.

The states have also tried to formulate a system to maintain regulation of firewood (nearly all states’ firewood regulations were based on the federal regulation of all hardwoods to prevent transport of the EAB). As part of this process, the NPB developed guidelines for adoption of regulations by the individual states (available here).  The NPB members are just beginning to explore whether  states might set up third-party certification system(s). Among the challenges to any harmonization are states’ differing legal authorities and disagreement on what threat levels should be applied, and for how long.

2) New information about the Asian longhorned beetle in South Carolina

ALB in South Carolina; photo by R. Brad Thompson, APHIS

South Carolina authorities reported that dendrological studies indicated Asian longhorned beetle (ALB) had been present near Charleston, S.C. since 2012, and possibly earlier. The population has the same genetic makeup as the outbreak in Ohio. This might be explained by either transport of infested wood from Clermont County, Ohio, or that wood packaging entering Charleston harbor came from the same part of China. (Charleston is an important port.) In South Carolina, ALB attacks primarily red maple – as is true at the other infestation sites. However, maple densities are much lower in the swamps of South Carolina and scientists don’t know whether the ALB will fly farther or intensify attacks on other host species. Other questions raised by differences between South Carolina and other, more northern, outbreak sites include possible changes in the beetle’s life cycle and flight periods.

Authorities noted the extremely difficult conditions, which impede survey and control efforts – which I described in an earlier blog.

One innovation was sharing of resources: staff from the North Carolina and Tennessee departments of agriculture went to South Carolina to help with surveys. The Resource Sharing Initiative was started a few years ago as a collaborative effort of APHIS and the NPB. This was the first time states tried it. There were several issues that had to be worked out. One issue was the long time it takes to train people to recognize ALB symptoms. All three states’ officials said the project was worthwhile.

black walnut in Fairfax County, VA — in an area where thousand cankers disease has been present for more than a decade; photo by FT Campbell

3) Recinding quarantines of thousand cankers disease of walnut

States which adopted quarantines targetting this insect/pathogen complex a decade ago now think that it poses little risk to black walnut (Juglans nigra) growing in its native range (as distinct from trees planted in the West). Several are in the process of rescinding their quarantines. I think these states have considered the science carefully and are taking the appropriate action.

4) Nursery self-certification – System Set Up; Will Nurseries Participate? Will Customers Support the Process?

Craig Regelbrugge of AmericanHort noted that the SANC program has now been officially launched – it has graduated from being a pilot program. [SANC stands for Systems Approach to Nursery Certification] Participants are exploring incentives to recruit wider participation by nurseries that produce plants and how to get support from plant retailers. SANC is conceived as an elite program for the best nurseries and marketplace leaders. It was never intended to be a remedial program to clean up problem issues such as the P. ramorum debacle. To work, it seems to me, SANC will need to find a way to persuade customers to want to pay more for quality plants. Hence the critical importance of getting retailers involved.

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

Resistance Breeding – a Useful Strategy

Port-Orford cedar resistance trials at Dorena Center; photo courtesy of Richard Sniezko, USFS

I have written several times about the importance of the United States adopting a comprehensive program to address all aspects of introduced forest pests including breeding of trees resistant to the introduced pests. See Fading Forests III from seven years ago; an earlier blog; and Bonello et al. 2020 (full citation at end of blog), in which we proposed the creation of a federal Center for Forest Pest Control and Prevention to implement end-to-end integrated responses to forest pest invasions. A similar view is being voiced internationally; see, e.g., Buggs et al. 2020.

I have seen efforts to restore pest-decimated tree species to the forest lagging. I complained in a recent blog link that the recent USDA Forest Service report on invasive species (Poland et al. 2021) gave a misleading impression that significant effort was being made on resistance breeding to address several pests.

The USFS does support breeding trees resistant to pests, but in my view this support has been inadequate – including in the USFS report. Others think so, too — see Sniezko and Koch 2017. This insufficiency only grows, despite USDA claims to recognize that promoting resistance to introduced forest pests is an essential component of achieving its strategic goals of maintaining or enhancing productivity while ensuring responsible stewardship of resilient natural resources (Federman and Zankowski 2019).

Work at the Dorena Genetic Research Center

The principal and most notable and successful resistance breeding effort has been the Dorena Genetic Resource Center. The Center was established by, and is funded through the USFS Region 6 Genetic Resource (part of the National Forest System) and Forest Health Management programs. The Center has a solid foundation in the expertise and facilities needed to carry out breeding efforts. Also, it has a 50-plus-year track record.

Dorena has supported breeding of white (five-needle) pines and Port-Orford cedar. Dorena also now provides expertise and some facilities to partners exploring a) breeding Oregon ash to resist the emerald ash borer and b) two Hawaiian trees (koa and ‘ōhi‘a) to resist introduced pathogens (see below). Dorena staff is assisting low-budget, shoe-leather efforts to explore breeding of other trees at risk to non-native pests. These programs are described briefly in Box 8 of Poland et al. 2021. Despite this valuable effort with proven success funding to continue Dorena’s work is tenuous.

White Pine Blister Rust — Efforts to develop resistance to white pine blister rust (WPBR) DMF in five-needle pine species (nine grow across the country) began more than 50 years ago. Currently Dorena focuses on whitebark pine (Pinus albicaulis), denizen of high elevations in the West, along with western white pine (P. monticola), sugar pine (P. lambertiana) , limber pine (P. flexilis), southwestern white pine (P. strobiformis), and foxtail pine (P. balfouriana). Testing whitebark for resistance to WPBR began in 2002. Seedling families from >1,300 parent trees are in various stages of testing. The discovery that some whitebark populations have much higher levels and frequency of partial resistance has allowed rapid distribution of seed. The first restoration plantings in the Pacific Northwest were in 2009.

3-year old seedlings of whitebark pine at Crater Lake National Park; photo by Richard Sniezko, USFS

There are many collaborators – especially the National Park Service, Washington State’s Department of Natural Resources, several Tribes, the Whitebark Pine Ecosystem Foundation, and American Forests. However, planting has been hampered by the high cost of restoration in these high elevation ecosystems, lack of frequent good seed crops on the resistant parent trees, and lack of approval to plant in designated wilderness areas. In the areas with the highest levels of resistant parents, management activities that encourage natural regeneration might be successful. In late 2020 the U.S. Fish and Wildlife Service proposed to list whitebark pine as a Threatened species

Oregon ash (F. latifolia) has not yet been attacked by the emerald ash borer, but all expect EAB to spread to the West coast. Dorena and cooperators have already collected seed from ash trees in Oregon and obtained funding for additional collections, to include Washington and California. The seeds are being stored at both Dorena and the USDA Agriculture Research Service facility at Ft. Collins, Colorado. Seedlings from two dozen families have also been planted at Dorena and a center operated by Washington State University, plus at a USFS Northern Research Station research center in Ohio, where EAB is established and they can be tested for resistance to the insect’s attack.

Koa and ‘ōhi‘a in Hawaii — Regeneration of the koa tree (Acacia koa) has been undercut by the koa wilt pathogen, Fusarium oxysporum f. sp. koae. Dorena initiated efforts with the Hawaii Agricultural Research Center (HARC) to respond in 2003. There has been rapid progress screening seedlings to identify resistant parent trees establishing seed orchards, delineating seed zones, and releasing seed with confirmed levels of resistance for reforestation and restoration (Sniezko and Koch 2017; see also Dudley et al. 2020).

‘ōhi‘a trees killed by rapid ‘ōhi‘a death; photo courtesy of J.R. Friday

When the threat to Hawaii`s most widespread tree ‘ōhi‘a (Metrosideros polymorpha) from rapid ‘ōhi‘a death (ROD) pathogens became apparent, the Dorena staff provided advice on breeding strategies. Its Center Geneticist is part of an ad hoc resistance team. Scientists have identified surviving trees in stands affected by ROD on the Big Island using a variety of methods. These include aerial surveys by drones and fixed-wing aircraft. They then began collecting seeds and cuttings. As of spring 2021, they have collected cuttings or seeds from more than 300 ‘ōhi‘a trees belonging to five varieties. The effort is low-cost, using Americorps volunteers coordinated by a single full-time person, a USFS employee. The program is still in its infancy. It will have to find funding to expand its scope to an operational resistance program once more information on resistance is has been obtained.

Other Efforts

Most other breeding programs are small and poorly funded. In fact, they have been described by one USFS scientist as “hobby projects” of a few scientists determined to try this strategy. Not only are efforts minimal; but also retirement of those few scientists can bring an end to the individual project.

There were greater efforts in the past. I have a document (of unknown origin) from 2011 that describes breeding efforts funded by both the National Forest System and USFS Research and Development. Table 1 listed 16 projects for western conifers; Table 2 listed 32 projects funded by R&D. During this period, the USFS provided start-up funds for the Healthy Forests Initiative, a consortium that sought to prove the concept that genetic engineering could quickly produce an American chestnut able to live and reproduce in its native range. This support was in addition to support for The American Chestnut Foundation backcross hybridization program link.

Part of the problem is the longstanding decline in funding and staffing of USFS research program. A graph in Chapter 6 of FFIII shows the decline in numbers of forest entomologists and pathologists over the 20-year period 1985–2007. Wheeler et al. 2015 discuss the parallel decline in tree breeders and geneticists (citation at end of this blog).

Cuts continue. Funding for research conducted by the USFS Research stations on ten non-native pests decreased from $10 million in Fiscal Year 2010 to just $2.5 million in Fiscal Year 2020 – a cut of more than 70%. I have lobbied for increased appropriations for decades.

The need for new approaches and increased effort is more widely asserted. One example is the group I am working with that promotes a new Center for Forest Pest Control and Prevention. Link A second example is the University of Florida’s recent conference of forest health researchers, representatives of the forest products industry, non-governmental organizations, and leaders of universities with forest-resource programs. This group suggested forming a united organization to increase capacity to improve forest health research. An article outlining the proposal is available here.

The Role of Biotechnology in Breeding Resistant Trees

what happened? same tree a few years apart — a TACF hybrid chestnut

Part of the discussion on forest research explores the proper role of biotechnology in tree species’ restoration. Purdue University hosted a related workshop in April 2021, in which I took part. (“Society and Policy Influences on Biotechnology Risk Assessment for Restoration of Threatened Forest Tree Species”). I hope participants will soon publish a paper based on our discussions.

Meanwhile, Revive & Restore, a wildlife conservation organization promoting the incorporation of biotechnologies into standard conservation practice, sponsored a workshop in June 2020. The 57 conservationists, wildlife biologists, restoration specialists, conservation geneticists, ethicists, and social scientists who participated agreed on an appropriate structure for using biotechnology. These included:

  • A broader definition of risk and application of new risk assessment tools;
  • Consideration of the risks of not taking action, as well as going ahead with a proposal;
  • Transparency about social and cultural values and engaging stakeholders
  • Monitoring results to ensure actions have been successful, manage uncertainty, and codify lessons learned.

In the literature I read, the workshops I participate in (e.g., National Academy of Sciences 2019; Purdue’s), biotechnology is seen as a potentially helpful set of tools that must be integrated into broader programs, all having research, tree improvement, restoration, and reforestation components. Such programs must have sustained management and resources stemming from public support. (For more complete descriptions of components of a resistance breeding program, see Sniezko and Koch 2017 (full reference below); or Chapter 6 of FFIII). Activities that must be incorporated include:

  • Germplasm collection and storage (applying the varied strategies that are appropriate);
  • Research to detect and test potential resistance or tolerance;
  • Research to identify techniques for producing propagules;
  • Planting sites that will be secure for decades;
  • Site preparation & planting;
  • Post-planting maintenance; and
  • Monitoring to determine success or problems

During the Purdue workshop, and in my writing, I have emphasized the principal hindrance to progress is the lack of resources being allocated to resistance breeding. USFS and academic scientists determined to pursue breeding approach must scrounge for funds. I describe some of their efforts below.

Collaborations on Breeding for Specific Species

(still) healthy hemlocks in Cook Forest State Park, Pennsylania; photo by F.T. Campbell

USFS Hemlock Woolly Adelgid (HWA) Initiative [apparently no website]

This initiative was developed under the leadership and direction of FHP staff. The list of cooperators includes dozens of state, federal, university and private organizations. The annual budget has averaged between $2.5 and $3.5 million. Most resources are apparently allocated to biocontrol, but some funding has been provided for breeding activities, including:

  • Seed collection and storage for both Carolina and eastern hemlocks. Two seed orchards have been established in western North Carolina. I believe they are protected from the hemlock woolly adelgid (HWA) by application of pesticides.
  • Research on these tree species’ silviculture and ecology, including manipulation of sunlight levels to protect seedlings from the adelgid and promote growth

The 2021-2025 Program – currently under review – foresees more integrated pest management applying biocontrol, chemical control, and silviculture. It aims to maintain the health of hemlocks being used in breeding programs and “explore” hemlock replacement options, such as hybrids or HWA-tolerant hemlocks (Mayfield et al. 2021). This effort is encouraging, but I have heard complaints from academics that they can’t get funding to pursue what they regard as promising breeding strategies.

Other small programs to breed resistant hemlocks are under way. The Forest Restoration Alliance (formerly the Alliance to Save Threatened Forests) asks citizens to identify surviving hemlocks and balsam firs. The Alliance has collected and propagated both cuttings and seeds and is testing their resistance.

Ash and Other Trees of the Upper Midwest

To date, few resources have been allocated to resistance breeding of ash. Between 2003 and 2017, only about 7% of research funds allocated to ash and emerald ash borer DMF have been devoted to host resistance. Of the host resistance research, 61% applied to identifying mechanisms, 14% to use of transgenics to develop resistance, only 7% (0.5% of the total research) has supported actual breeding for resistance (Sniezko and Koch 2017).

In May 2021 the USFS announced it was seeking funds from the water-focused Great Lakes Restoration Initiative. The USFS expects to receive up to $5.4 million for reforestation, ecosystem restoration. and forest health improvements on non-federal lands in the Great Lakes basin. (This includes parts of the states of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania and Wisconsin). The announcement doesn’t mention resistance breeding for ash, beech, hemlock, or other trees in the region. I hope some of the new funds will be allocated to this strategy.

“lingering” ash; photos courtesy of Jennifer Koch, USFS

In an encouraging show of entrepreneurship, USFS scientists and others have formed the Great Lakes Basin Forest Health Collaborative – a partnership with Holden Forests and Gardens, American Forests, and USFS (Kappler et al. 2021). The purpose of the Collaborative is to advance resistance breeding for these important tree species. The initial focus is on the five ash species in the region, especially black ash (Fraxinus nigra) link to blog The Collaborative is recruiting a network of partners, and will provide training and technology transfer. The partners will provide volunteers and other resources. Partners do not have to be within the region if their work helps the Great Lakes Basin, but plantings have to be there.

Partners will help identify survivor trees with potential resistance (e.g., “lingering” ash); establish clone banks and/or seed orchards; and manage seed collections. Each partner will operate independently, but in collaboration with the others. The initial focus is on obtaining representative seed collections of ash and hemlock. Then cloning, testing resistance, and crosses can begin. Eventually select lines will be chosen for bulking up and reintroduction.

In future the Collaboration hopes to engage in breeding hemlocks and identifying beech trees that remain healthy in areas heavily impacted by beech leaf disease (BLD).

Other efforts under way include the Monitoring and Managing Ash (MaMA) Program, based in the Ecological Research Institute in New York State.

Beech trees with resistance to beech bark disease (BBD) were identified as early as the 1980s, but a breeding program was begun only in 2002. A collaborative, multi-agency effort has resulted in the establishment of five regional American beech seed orchards with four others in progress as of 2017. Partners provide a cost-effective process for identifying resistant parent trees. State and National Forest personnel surveyed natural forests for candidate trees and then tested each tree and identified markers associated with resistance (Sniezko and Koch 2017).

Challenges Beyond Breeding

Large-scale restoration of tree species across much of their ranges will require significant inputs of funds, over long time periods, as well as resolving daunting logistical issues.

Some think the most likely scenario will be to plant focal areas, or islands, that can aid future natural regeneration (Sniezko and Koch 2017). The American Chestnut Foundation (TACF) anticipates it will take 1,000 years to re-establish American chestnut DMF across its range through a process of three phases: long-term research and demonstration plantings; a relatively small-scale public horticultural program using trees and/or pollen made available by TACF; and a larger-scale public restoration program using progeny from years of outcrossing and production. (This assumes APHIS approves release of the transgenic “Darling 58” tree, plus – I believe – progress in developing resistance to root disease caused by Phytophthora cinnamomi). Already good progress using focal areas has started with several white pine species, and a national plan is in the works for whitebark pine.

Such efforts will require access to land that can be protected from other uses, e.g., development for decades or centuries. Also it will require management of sites to protect propagules from browsing wildlife (deer, rabbits!), provide adequate water and light, and probably give plantings a competitive advantage in relation to other plants growing there …

non-resistant elms will grow anywhere! photo by F.T. Campbell

And there is the issue of how a relatively small number of resistant propagules will succeed in spreading their improved genetics in areas where non-improved elm, ash, beech and hemlock are reproducing naturally. Is reproduction of unimproved trees likely to continue in the face of new and old pests’ spread? If biocontrol agents succeed in reducing a pest’s impact on a host tree species, will that enhance the competitive ability of unimproved trees to the disadvantage of genetically improved conspecifics? What are realistic expectation for programs, and for their success?

Criteria for Success

Woodcock, Marzano, and Quine (2019) analyzed five breeding programs to identify aspects that contribute to success. Four of the programs were in North America; they targetted chestnut, western white pines, and Sitka spruce & white pine weevil. They concluded that 

  • Success is influenced by the level of resistance present in individual trees, the frequency of resistance in the population, and the heritability of resistance.
  • It is important to consider current and potential future risks to the species in addition to the target pest or pathogen— the benefits of trees resistant to a specific threat are negated if it is susceptible to other threats.
  •  Demand [for a resistant tree to plant] should be evaluated, and the priorities of potential supporters and end users should inform the methods used to produce resistant trees.
  •  Operational deployment should balance the urgency of the threat with the consequences if resistant material does not perform as hoped. Urgency might differ for an emerging pest or pathogen.
  • Deployment strategies should be informed by the risks of imposing a strong selection pressure on the pest or pathogen to evolve to overcome host resistance, and by potential impacts on partially resistant trees.
  • Continued monitoring of field performance is important for evaluation, and can help to identify and mitigate emerging threats (e.g. new pathogen strains).

SOURCES

Bonello, P., F.T. Campbell, D. Cipollini, A.O. Conrad, C. Farinas, K.J.K. Gandhi, F.P. Hain, D. Parry, D.N. Showalter, C. Villari, and K.F. Wallin. 2020. Invasive tree pests devastate ecosystems – A proposed new response framework. Frontiers in Forests and Global Change. January 2020. Volume 3, Article 2 

Buggs, R.J.A. 2020 Changing perceptions of tree resistance research. Plants, People, Planet. 2020; 2: 2– 4. https://doi.org/10.1002/ppp3.10089

Dudley, N.; Jones, T.; Gerber, K.; Ross-Davis, A.L.; Sniezko, R.A.; Cannon, P.; Dobbs, J. 2020. Establishment of a Genetically Diverse, Disease-Resistant Acacia koa A. Gray Seed Orchard in Kokee, Kauai: Early Growth, Form, and Survival. Forests 2020, 11, 1276

Federman, S. and P. Zankowski. 2019. Strategic science planning for responsible stewardship and plant protection at the U.S. Department of Agriculture. Plants, People, Planet © New Phytologist Trust 2019;00:1–4. https://doi.org/10.1002/ ppp3.10075

Kappler, R., C. Blashka, D. burke, E. Hall, C. Pike, J. Koch. 2021. Great Lakes Basin Forest Health Collaborative: What it’s all about. North American Forest Insect Work Conference 28 May 2021

Mayfield, A.E. III, Salom, S., Jetton, R., Havill, N., Rhea, R., and Mausel, D. 2021. North American Forest Insect Work Conference 28 May 2021. Spread, impact and management of HWA in eastern North America

National Academies of Sciences, Engineering, and Medicine. 2019. Forest Health and Biotechnology: Possibilities and Considerations. Washington, DC: The National Academies Press. https://doi.org/10.17226/25221.

Poland, T.M., P. Patel-Weynand, D.M Finch, C.F. Miniat, D.C. Hayes, V.M Lopez, editors. 2021. Invasive Species in Forests and Rangelands of the United States. A Comprehensive Science Synthesis for the US Forest Sector. Springer

Sniezko, R.A. and J. Koch. 2017. Breeding trees resistant to insects & diseases: putting theory into application. Biol Invasions. 2017. 19:3377-3400. DOI 10.1007/s10530-017-1482-5

Wheeler, N.C., K.C. Steiner, S.E. Schlarbaum, D.B. Neale. 2015. The Evolution of Forest Genetics and Tree Improvement Research in the United States, Journal of Forestry, Volume 113, Issue 5, September 2015, Pages 500–510, https://doi.org/10.5849/jof.14-120

Woodcock, P., M. Marzano, C.P. Quine. 2019. Key lessons from resistant tree breeding programmes in the Northern Hemisphere. Annals of Forest Science (2019)76:51 https://doi.org/10.1007/s13595-019-0826-y

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

On the Rise: US Imports & the Risks of Tree-killing Pests

containers at Port of Long Beach; photo courtesy of Bob Kanter, Port of Long Beach

Here I update information on two of the major pathways by which tree-killing pests enter the United States: wood packaging and living plants (plant for planting).

Wood Packaging

Looking at wood packaging material, we find rising volumes for both shipping containers – and their accompanying crates and pallets; and dunnage.

Crates and pallets – Angell (2021; full citation at the end of the blog) provides data on North American maritime imports in 2020. The total number of TEUs [a standardized measure for containerized shipment; defined as the equivalent of a 20-foot long container] entering North America was 30,778,446.U.S. ports received 79.6% of these incoming containers, or 24,510,990 TEUs. Four Canadian ports handled 11.4% of the total volume (3,517,464 TEUs; four Mexican ports 8.9% (2,749, 992 TEU). Angell provides data for each of the top 25 ports, including those in Canada and Mexico.

To evaluate the pest risk associated with the containerized cargo, I rely on a pair of two decade-old studies.  Haack et al. (2014) determined that approximately 0.1% (one out of a thousand) shipments with wood packaging probably harbor a tree-killing pest. Meissner et al. (2009) found that about 75% of maritime shipments contain wood packaging. Applying these calculations, we estimate that 21,000 of the containers arriving at U.S. and Canadian ports in 2020 might have harbored tree-killing pests.

While the opportunity for pests to arrive is obviously greatest at the ports receiving the highest volumes of containers with wood packaging, the ranking (below) does not tell the full story. The type of import is significant. For example, while Houston ranks sixth for containerized imports, it ranks first for imports of break-bulk (non-containerized) cargo that is often braced by wooden dunnage (see below). Consequently, Houston poses a higher risk than its ranking by containerized shipment might indicate.

Also, Halifax Nova Scotia ranks 22nd for the number of incoming containerized shipments (258,185 containers arriving). However, three tree-killing pests are known to have been introduced there: beech bark disease (in the 1890s), brown spruce longhorned beetle (in the 1990s), and European leaf-mining weevil (before 2012) [Sweeney, Annapolis 2018]

The top ten ports receiving containerized cargo in 2020 were

Port                                         2020 market share                2020 TEU volume

Los Angeles                           15.6%                                      4,652,549

Long Beach                            13%                                         3,986,991

New York/New Jersey         12.8%                                      3,925,469

Savannah                             7.5%                                        2,294,392

Vancouver BC                        5.8%                                        1,797,582

Houston                                   4.2%                                        1,288,128

Manzanillo, MX                      4.1%                                        1,275,409

Seattle/Tacoma    4.1%                                        1,266,839

Virginia ports                        4.1%                                        1,246,609

Charleston                             3.3%                                        1,024,059

Import volumes continue to increase since these imports were recorded. U.S. imports rose substantially in the first half of 2021, especially from Asia. Imports from that content reached 9,523,959 TEUs, up 24.5% from the 7,649,095 TEUs imported in the first half of 2019. The number of containers imported in June was the highest number ever (Mongelluzzo July 12, 2021).

Applying the calculations from Haack et al. (2014) and Meissner et al. (2009) to the 2021 import data, we find that approximately 7,100 containers from Asia probably harbored tree-killing pests in the first six months of the year. (The article unfortunately reports data only for Asia.) Industry representatives quoted by Mongelluzzo expect high import volumes to continue through the summer. This figure also does not consider shipments from other source regions.

Dunnage on the pier at Port of Houston; photo by Port of Houston

Infested dunnage – Looking at dunnage, imports of break-bulk (non-containerized) cargo to Houston – the U.S. port which receives the most – are also on the upswing. Imports in April were up 21% above the pandemic-repressed 2020 levels.

Importers at the port complain that too often the wooden dunnage is infested by pests, despite having been stamped as in compliance with ISPM#15. CBP spokesman John Sagle confirms that CBP inspectors at Houston and other ports are finding higher numbers of infested shipments. CBP does not release those data, so we cannot provide exact numbers (Nodar, July 19, 2021).

The Houston importers’ suspicion has been confirmed by data previously provided by CBP to the Continental Dialogue on Non-Native Insects and Diseases. From Fiscal Year 2010 through Fiscal Year 2015, on average 97% of the wood packaging (all types) found to be infested bore the stamp. CBP no longer provides data that touch on this issue.

Detection of pests in the dunnage leads to severe problems. Importers can face fines up to the full value of the associated cargo. Often, the cargo is re-exported, causing disruption of supply chains and additional financial losses (Nodar, July 19, 2021).

In 2019 importers and shippers from the Houston area formed an informal coalition with the Cary Institute of Ecosystem Studies to try to find a solution to this problem. The chosen approach is for company employees to be trained in CBP’s inspection techniques, then apply those methods at the source of shipments to identify – and reject – suspect dunnage before the shipment is loaded.  In addition, the coalition hopes that international inspection companies, which already inspect cargo for other reasons at the loading port will also be trained to inspect for pests.  Steps to set up such a training program were interrupted by the COVID-19 pandemic, but are expected to resume soon (Nodar, July 19, 2021).

Meanwhile, the persistence of pests in “treated” wood demands answers to the question of “why”. Is the cause fraud – deliberate misrepresentations that the wood has been treated when it has not? Or is the cause a failure of the treatments – either because they were applied incorrectly or they are inadequate per se?

ISPM#15 is not working adequately. I have said so.  Gary Lovett of the Cary Institute has said so (Nodar July 19, 2021). Neither importers nor regulators can rely on the mark to separate pest-free wood packaging from packaging that is infested.

APHIS is the agency responsible for determining U.S. phytosanitary policies. APHIS has so far not accepted its responsibility for determining the cause of this continuing issue and acting to resolve it. Preferably, such detection efforts should be carried out in cooperation with other countries and such international entities as the International Plant Protection Convention (IPPC) and International Union of Forest Research Organizations (IUFRO). However, APHIS should undertake such studies alone, if necessary.

In the meantime, APHIS and CBP should assist importers who are trying to comply by facilitating access to information about which suppliers often supply wood packaging infested by pests. The marks on the wood packaging includes a code identifying the facility that carried out the treatment, so this information is readily available to U.S. authorities.

Plants for Planting

A second major pathway of pest introduction is imports of plants for planting. Data on this pathway are too poor to assess the risk – although a decade ago it was found that the percentage of incoming shipments of plants infested by a pest was 12% – more than ten times higher than the proportion for wood packaging (Liebhold et al. 2012).

According to APHIS’ annual report, in 2020 APHIS and its foreign collaborators inspected 1.05 billion plants in the 23 countries where APHIS has a pre-clearance program. In other words, these plants were inspected before they were shipped to the U.S.  At U.S. borders, APHIS inspected and cleared another 1.8 billion “plant units” (cuttings, rooted plants, tissue culture, etc.) and nearly 723,000 kilograms of seeds. Obviously, the various plant types carry very different risks of pest introduction, so lumping them together obscures the pathway’s risk. The report does not indicate whether the total volume of plant imports rose or fell in 2020 compared to earlier years.

SOURCES

Angell, M. 2021. JOC Rankings: Largest North American ports gained marke share in 2020. June 18, 2021. https://www.joc.com/port-news/us-ports/joc-rankings-largest-north-american-ports-gained-market-share-2020_20210618.html?utm_campaign=CL_JOC%20Port%206%2F23%2F21%20%20_PC00000_e-production_E-103506_TF_0623_0900&utm_medium=email&utm_source=Eloqua

Haack R.A., Britton K.O., Brockerhoff, E.G., Cavey, J.F., Garrett, L.J., et al. (2014) Effectiveness of the International Phytosanitary Standard ISPM No. 15 on Reducing Wood Borer Infestation Rates in Wood Packaging Material Entering the United States. PLoS ONE 9(5): e96611. doi:10.1371/journal.pone.0096611

Liebhold, A.M., E.G. Brockerhoff, L.J. Garrett, J.L. Parke, and K.O. Britton. 2012. Live Plant Imports: the Major Pathway for Forest Insect and Pathogen Invasions of the US. www.frontiersinecology.org

Meissner, H., A. Lemay, C. Bertone, K. Schwartzburg, L. Ferguson, L. Newton. 2009. Evaluation of Pathways for Exotic Plant Pest Movement into and within the Greater Caribbean Region. A slightly different version of this report is posted at 45th Annual Meeting of the Caribbean Food Crops Society https://econpapers.repec.org/paper/agscfcs09/256354.htm

Mogelluzzo, B. July 12, 2021. Strong US imports from Asia in June point to a larger summer surge.

Nodar, J. July 19, 2021. https:www.joc.com/breakbulk/project-cargo/breakbult-volume-recovery-triggers-cbp-invasive-pest-violations_20210719.htm 

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

USFS report: treatment of introduced forest pests

still-healthy hemlocks in Cook Forest State Park, PA; photo by F.T. Campbell

In February the USFS published a lengthy analysis of invasive species: Invasive Species in Forests and Rangelands of the United States. A Comprehensive Science Synthesis for the US Forest Sector (Poland et al. 2021; full citation at the end of the blog). The book is available for download at no cost here.

In a separate blog, I evaluated several aspects of the report as they apply to invasive species generally. Here I focus on invasive insects and pathogens that attack North American tree species (that is, forest pests).

As I said in the separate blog, I doubt that the book will stimulate policy-makers to increase Forest Service resources allocated to invasive species research, much less management. Sections 14.5 and 16.5 of the report state that the continued absence of a comprehensive investigation of the impacts of invasive species, especially the full value of ecosystem services lost, is a barrier to policymakers seeking to develop priorities and realistic management strategies.

I think the book’s editors tried to provide as much information about impacts as possible given existing knowledge. But the book’s length, comprehensive inclusion of all bioinvaders, organizational structure, and the detailed discussions of theories and models reduce the contribution the book might make to management decisions. I did not find “lessons learned” that could be applied in the policy realm. 

Chapters address impacts in terrestrial and aquatic systems; impacts on ecosystem processes; impacts on various sectors of the economy and cultural resources; interactions with climate change and other disturbances; management strategies for species and landscapes; tools for inventory and management. Each chapter evaluates the current status of knowledge about the topic and suggests research needs. There are also summaries of the invasive species situation in eight regions.

The choice to organize the book around the chapters listed above means that some information one might expect to find in a book about invasive species is scattered or even absent. This is not a good resource for concise descriptions of individual invasive species and their impacts. That information is scattered among the chapters depending on whether some aspect of the species was chosen to illustrate a scientific challenge or success. The regional summaries partially remedy this problem – but they do not provide perspective on organisms that have invaded more than one region, e.g., emerald ash borer or white pine blister rust. To some extent, information about individual species is provided in the several subchapters on forest insects and pathogens. Or the reader of the PDF version can use the word search function!

Of course, information on several individual high-profile bioinvaders can be found in other publications; see the species write-ups and references posted at www.dontmovefirewood.org. Under these circumstances, a description of invasive species impacts from the ecosystem perspective is a welcome addition. I have long wished for a “crown to root zone” description of invasive species’ impacts.

HWA-killed hemlocks in Linville Gorge, NC; photo by Steven Norman, USFS

In this blog, I will focus on issues that the report raises that I found most interesting.

Information in the Report on Invasive Insects & Pathogens that Attack North American Trees

At several places the report states that non-native pests that have the potential to threaten the survival of an entire tree genus should be a high priority (p. 136) (what actions should be prioritized are not specified). They name the emerald ash borer (EAB) and Dutch elm disease. Elsewhere, EAB and hemlock woolly adelgid (HWA) are described as among the most significant threats to forests in the Eastern U.S. While EAB and HWA have certainly received considerable attention from the Forest Service, threats to elm have not. (I regret that the timing of the report precluded reference to Kevin Potter’s priority-setting publication. Potter is not listed as a co-author of the book.)

Hemlock woolly adelgid, emerald ash borer, chestnut blight, white pine blister rust (WPBR), and laurel wilt are cited as examples of highly virulent, host-specific agents that kill dominant, abundant, and ecologically unique hosts (p.18), resulting in exceptionally severe long-term impacts. WPBR and HWA specifically can have profound and far-reaching negative effects on ecosystem structure and function. These can rise to the level of an irreversible change of ecological state (p. 97). Of this list, no federal agency has allocated many resources to efforts to slow the spread of laurel wilt. The Forest Service is certainly tracking its spread and impacts.

Exaggerations or Errors

I think the report exaggerates the level of resources allocated to host resistance breeding. The report mentions programs targetting Dutch elm disease, beech bark disease, EAB, HWA and laurel wilt. It describes programs for white pines and Port-Orford cedar as examples of success. However, I would say that all the programs, except American chestnut, are starved for funds and other resources. The report’s authors concede this on p. 195.

TACF American chestnut in field trial; photo by F.T. Campbell

I think the report is too optimistic about the efficacy – so far – of biocontrol agents targeting HWA & EAB. On the other hand, I appreciate the report’s recognition that application of augmentative biocontrol of the Sirex woodwasp is more complicated in North America than in Southern Hemisphere countries (p. 162).

I am concerned about the statement that many plant pathogens are transported, but few have major impact. Examples in the U.S. are said to be WPBR, chestnut blight, and Phytophthora ramorum (p. 97). However, the report does not mention laurel wilt – which has a broad host range; nor rapid ‘ōhi‘a death — which threatens the most widespread tree species on the Hawaiian Islands. Nor does it mention several pathogens attacking single tree species, including beech bark disease, Port-Orford cedar root disease, and butternut canker. The report was written before recognition of beech leaf disease. The report notes that the three diseases it did mention have huge impacts. I am greatly disappointed that the report does not address how scientists and managers should deal with this “black swan” problem other than long discussions of data gaps, and ways to improve models of introduction and spread.

In addition, I am concerned that the discussion of economic factors that influence trade flows and accompanying invasive species (p. 308) focusses too narrowly on inspection alone, rather than other strategies for curtailing introduction. This section also shortens a description of the point made in Lovett et al. (2016). The report notes that Lovett et al. (2016) say that rates of introduction of wood-boring species decreased after ISPM#15 was implemented. However, the report leaves out the major caveat in that paper and the studies by Haack et al. (2014) and Leung et al. (2014) on which it is based: the reduction was insufficient to protect America from damaging introductions! [A further error has crept in: the Haack study explicitly excluded imports from China from their calculations. The Lovett paraphrase is not really clear on this matter.]

Curiosities/Concerns Re: Regional Write-Ups

I wish the sections on the Northwest and Southwest region discussed why areas with so many characteristics favoring introduction of plant pests – major ports, extensive transportation networks, major horticultural industry, extensive agriculture, and abundant urban and native forests – have so few damaging forest pests. (Admittedly, those present are highly damaging: white pine blister rust, sudden oak death, Port-Orford cedar root disease, pitch canker, balsam woolly adelgid, larch casebearer, polyphagous shot hole borer (I add Kuroshio shot hole borer), and banded elm bark beetle). The report does mention the constant threat of introduction of the European and Asian gypsy moths. (The Entomological Society of America has decided to coin a new common name for these insects; they currently to be called by the Latin binomial Lymatria dispar). The report notes that 22 species of non-native bark and ambrosia beetles have recently been introduced in the Southwest.

The report cites a decade-old estimate by Aukema et al. (2010) in saying that a small proportion of introduced pest species has killed millions of trees or pushed ecologically foundational species toward functional extinction. The figure was 14% of the more than 450 non-native forest insect species. I greatly regret that overlapping preparation and publication periods precluded inclusion of data from studies by Potter, Guo, and Fei.  http://nivemnic.us/what-fia-data-tell-us-about-non-native-pests-of-americas-forests/

Section 7.3 of the report discusses frameworks for setting priorities. It identifies five factors: 1) pest species having the greatest negative impacts; 2) uniqueness of the affected ecosystem or community; 3) state of the invasion in space and time; 4) management goals; 5) availability of effective tools. Examples of species meeting these criteria include EAB and Dutch elm disease (pest threatens entire host genus); white pine blister rust on whitebark pine (key species in a system with low arboreal diversity).

The report notes increasing understanding of critical aspects of several important pests’ biology and host interactions – but it does not sufficiently acknowledge the decades of effort required to achieve this knowledge. The time required for additional scientific advances will probably be equal or greater, given falling number of “ologists” in government and academia.

I appreciate inclusion of a discussion (Sections 8.3.1 and 8.3.2) on breeding trees resistant to introduced pests

dead Port-Orford cedar in Redwoods National Park; photo by Richard Sniezko, USFS

This section states that host resistance, forest genetics, and tree improvement might be the most effective approaches to managing many established pests. The section says such breeding does not require the use of genetically modified organisms, although transgenic or gene editing technologies can provide useful tools. I appreciate the report conceding that necessary infrastructure and expertise has been declining for two decades (p. 195).

In discussing international cooperation to reduce transport of invasive species, the report refers to increasing availability of data allowing identification of potentially damaging species in their regions of origin. Again, since this chapter was written, the Forest Service has increased its engagement on this approach: the USFS International Program is supporting sentinel plantings managed by the International Plant Sentinel Network (http://www.plantsentinel.org) … see my recent blog here.

SOURCE

Poland, T.M., P. Patel-Weynand, D.M Finch, C.F. Miniat, D.C. Hayes, V.M Lopez, editors. 2021. Invasive Species in Forests and Rangelands of the United States. A Comprehensive Science Synthesis for the US Forest Sector. Springer

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

USFS invasive species report: Herculean effort that could have had greater impact

In February the USFS published a lengthy analysis of invasive species: Invasive Species in Forests and Rangelands of the United States. A Comprehensive Science Synthesis for the US Forest Sector (Poland et al. 2021; full citation at the end of the blog). More than 100 people contributed to the book; I helped write the chapters on legislation and regulations and international cooperation. The book is available for download at no cost here.

Chapters address impacts in terrestrial and aquatic systems; impacts on ecosystem processes; impacts on various sectors of the economy and cultural resources; interactions with climate change and other disturbances; management strategies for species and landscapes; tools for inventory and management. Each chapter evaluates the current status of knowledge about the topic and suggests research needs. There are also summaries of the invasive species situation in eight regions.

Miconia – one of many invasive plants damaging ecosystems in Hawai`i

I greatly appreciate the effort. Authors first met in 2015, and most chapters were essentially written in 2016. The long delay in its appearance came largely from negotiations with the publisher. The delay means some of the information is out of date. I am particularly aware that several experts – e.g., Potter, Guo, and Fei – have published about forest pests since the Aukema source cited. I wonder whether inclusion of their findings might change some of the conclusions about the proportion of introduced pests that cause noticeable impacts.

Since the report’s publication in February I have struggled with how to describe and evaluate this book. What is its purpose? Who is its audience? The Executive Summary says the report is a sector-wide scientific assessment of the current state of invasive species science and research in the U.S.

However, the Introduction states a somewhat different purpose. It says the report documents invasive species impacts that affect ecosystem processes and a wide range of economic sectors. This would imply an intention to enhance efforts to counter such effects– not just to shape research but also to change management. Indeed, the Conclusion of the Executive Summary (pp. xvi-xvii) is titled “An Imperative for Action”.

Tom Vilsack, Secretary of Agriculture

I am not the author to evaluate how effectively the book sets out research agendas. Regarding its usefulness in prompting policy-makers to do more, I regretfully conclude that it falls short.

Getting the balance right between an issue’s status and what needs to be done is difficult, perhaps impossible. I appreciate that the report makes clear how complex bioinvasion and ecosystem management and restoration are. Its length and density highlight the difficulty of making progress. This daunting complexity might well discourage agency leadership from prioritizing invasive species management.

On the other hand, summary sections sometimes oversimplify or bury important subtleties and caveats. The question of whether some key questions can ever be resolved by science is hinted at – but in detailed sections that few will read. The same is true regarding the restrictions imposed by funding shortfalls.

The Report Would Have Benefitted from Another Round of Editing

Editing this tome was a Herculean task. I feel like a curmudgeon suggesting that the editors do more! Nevertheless, I think the report would have been improved by the effort. One more round of editing – perhaps involving a wider range of authors – could have pulled together the most vital points to make them more accessible to policymakers. It could also have tightened the ecosystem-based descriptions of impacts, which are currently overwhelmed by too much information.

A precis for policymakers

A precis focused on information pertinent to policymakers (which the current Executive Summary does not) should contain the statement that the continued absence of a comprehensive investigation of invasive species’ impacts hampers research, management, and policy (mentioned only in §16.5, on p. 332). It should note situations in which insufficient funding is blocking recommended action. I note three examples: programs aimed at breeding trees resistant to non-native pests (resource issues discussed only in §§8.3.1 and 8.3.2, p. 195); sustaining “rapid response” programs (§6.4.3, p. 125); costs of ecosystem restoration, especially for landscape-level restoration (§16.4). I am sure there are additional under-funded activities that should be included!

cross-bred ash seedlings being tested for vulnerability to EAB; photo courtesy of Jennifer Koch

 Other important information that should be highlighted in such a precis includes the statement that many ecosystems have already reached a point where healthy functions are in a more tenuous balance due to invasive species (p. 51). Effective carbon storage and maintaining sustainable nutrient and water balance are at risk. Second, costs and losses caused by invasive forest pests generally fall disproportionately on a few economic sectors and households. They cannot be equated to governmental expenditures alone (p. 305).  Third, even a brief estimate of overall numbers of invasive species appears only in §7.4. Information about individual species is scattered because it is used as example of particular topic (e.g., impacts on forest or grassland ecosystems, or on ecosystem services, or on cultural values).

Ecosystem Impacts Overwhelmed

As noted above, the report laments the absence of a comprehensive investigation of invasive species’ impacts. Perhaps the editors intended this report to partially fill this gap. To be fair, I have long wished for a “crown to root zone” description of invasive species’ impacts at a site or in a biome. Concise descriptions of individual invasive species and their impacts are not provided by this report, but they can be found elsewhere. (The regional summaries partially address the problem of too much information – but they do not provide perspective on organisms that have invaded more than one region, e.g., emerald ash borer or white pine blister rust.) Another round of editing might have resulted in a more focused presentation that would be more easily applied by policymakers.

Welcome Straightforward Discussion of Conceptual Difficulties

I applaud the report’s openness about some important overarching concepts that science cannot yet formulate.  If supportable theories could be conceived, they would assist in the development of policies:

  • Despite decades of effort, scientists have not established a clear paradigm to explain an ecosystem’s susceptibility to invasion (p. 85). Invasibility is complex: it results from a dynamic interplay between ecosystem condition and ecological properties of the potential invader, especially local propagule pressure.
  • Scientists cannot predict how climate warming will change distributions of invasive species [see Chapter 4] and alter pathways. This inability hampers efforts to develop effective prevention, control, and restoration strategies (p. xi). Climate change and invasive species need to be studied together as interactive drivers of global environmental change with evolutionary consequences.

The Report’s Recommendations

Policy-oriented recommendations are scattered throughout the report. I note here some I find particularly important:

  • Measures of progress should be based on the degree to which people, cultures, and natural resources are protected from the harmful effects of invasive species.
  • Managers should assess the efficacy of all prevention, control, and management activities and their effect upon the environment. Such an evaluation should be based on a clear statement of the goals of the policy or action. [I wish the report explicitly recognized that both setting goals and measuring efficacy are difficult when contemplating action against a new invader that is new to science or when the impacts are poorly understood. Early detection / rapid response efforts are already undermined by an insistence on gathering information on possible impacts before acting; that delay can doom prospects for success.]
    • Risk assessment should both better incorporate uncertainty and evaluate the interactions among multiple taxa. Risk assessment tools should be used to evaluate and prioritize management efforts and strategies beyond prevention and early detection/rapid response.
    • Economic analyses aimed at exploring tradeoffs need better tools for measuring returns on invasive species management investments (§16.5).
  • Actions that might be understood as “restoration” aim at a range of goals along the gradient between being restored to a known historic state and being rehabilitated to a defined desired state. The report stresses building ecosystem resilience to create resistance to future invasions, but I am skeptical that this will work re: forest insects and disease pathogens.
  • Propagule pressure is a key determinant of invasion success. Devising methods to reduce propagule pressure is the most promising to approach to prevent future invasions (p. 115). This includes investing in quarantine capacity building in other countries can contribute significantly to preventing new invasions to the US.
  • Resource managers need additional studies of how invasive species spread through domestic trade, and how policies may differ between foreign and domestic sources of risk.

I appreciate the report’s attention to such often-ignored aspects as non-native earthworms and soil chemistry. I also praise the report’s emphasis on social aspects of bioinvasion and the essential role of engaging the public. However, I think the authors could have made greater use of surveys conducted by the Wisconsin Department of Natural Resources and The Nature Conservancy’s Don’t Move Firewood program.

Lost Opportunities

I am glad that the report makes reference to the “rule of 25” rather than “rule of 10s”. I would have appreciated a discussion of this topic, which is a current issue in bioinvasion theory. As noted at the beginning of this blog, the long time between when the report was written and when it was published might have hampered such a discussion

Also, I wish the report had explored how scientists and managers should deal with the “black swan” problem of infrequent introductions that have extremely high impacts. The report addresses this issue only through long discussions of data gaps, and ways to improve models of introduction and spread.

I wish the section on the Northwest Region included a discussion of why an area with so many characteristics favoring bioinvasion has so few damaging forest pests. Admittedly, those present are highly damaging: white pine blister rust, sudden oak death, Port-Orford cedar root disease, balsam woolly adelgid, and larch casebearer. The report also notes the constant threat that Asian and European gypsy moths will be introduced. (The Entomological Society of America has decided to coin a new common name for these insects; they currently to be called by the Latin binomial Lymatria dispar).

And I wish the section on the Southeast and Caribbean discussed introduced forest pests on the Caribbean islands. I suspect this reflects a dearth of research effort rather than the biological situation. I indulge my disagreement with the conclusion that introduced tree species have “enriched” the islands’ flora.

SOURCE

Poland, T.M., P. Patel-Weynand, D.M Finch, C.F. Miniat, D.C. Hayes, V.M Lopez, editors. 2021. Invasive species in Forests and Rangelands of the United States. A Comprehensive Science Synthesis for the US Forest Sector. Springer

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm