I report here on recent developments on breeding resistant trees. These include both promising results from decades-long efforts and also a promising start to addressing a new challenge.
These programs have benefited from major commitments by the USDA Forest Service. I hope they encourage similar commitments for other priority species – such as those named by the CAPTURE program.
Port-Orford cedar – ready to be planted in the forest!
Scientists who have been working for decades to breed seedlings of Port-Orford cedar (POC) trees resistant to the root rot caused by Phytophthora lateralis https://www.dontmovefirewood.org/pest_pathogen/port-orford-cedar-root-disease-html/now say that they have seedlings ready for planting in the forest. They made this case in a webinar in late February. It can be viewed here. The full webinar runs somewhat over two hours.
The scientist who led early studies of POC and the root disease, Don Zobel, Professor Emeritus, Oregon State University, described the ecological requirements that should guide planting programs. POC produces high-calcium litter. It grows from the sea coast to 1950 meters elevation, on sand dunes, fens, soils with hardpans; mafic & ultramafic rocks (serptentines) and fertile soils on some sedimentary rocks. POC is less shade tolerant than western hemlock but more fire tolerant. It can form a secondary canopy under Douglas-fir and supercede other conifers when fire occurs repeatedly. The tree needs surface water, e.g., seepages and stream sides; but the water must be flowing, not stagnant. Seedlings are especially vulnerable to drying during winter.
[I posted a separate blog about other trees native to this region, including serpentine soils, here.]
One purpose of the webinar was to encourage owners and managers of lands within POC’s historic range (see the map under Dr. Zobel’s presentation) to begin planting the species in appropriate sites. With this in mind, Dr. Zobel emphasized criteria for selecting sites:
Climates in coastal areas of the range are less likely to change under climate change
Quartenary marine terraces are the best geologic type; Lookingglass and Roseburg geologic types are also acceptable
Availability of water during summer, e.g., streamside and seepage areas. Try planting beneath alder. However, avoid interior valley stream corridors if the soils are not ultramafic. And avoid stagnant water.
a POC tree in a bog next to the endemic pitcher plant of southern Oregon, Darlingtoniacalifornica; photo by Richard Sniezko
Dr. Zobel also says one should plant pathogen-resistant genotypes and pay attention to local genetic varieties (which have largely been determined).
Dr. Richard Sniezko of the USFS Dorena Genetic Resource Center described the Center’s 30-year effort to find and exploit resistance to the pathogen. Funding has come from the USFS Forest Health Protection program, other parts of the USFS, and the Bureau of Land Management (BLM). The goal all along has been to produce seedlings for restoration to the forest – meaning not just resistant to the pathogen but also adapted to various local conditions. The program can now provide resistant seedlings in large quantities for planting by landowners and public land managers.
Dr. Sniezko emphasizes that success depends on engagement of four sets of people: research by university scientists; application of that research and development of propagule growing methods by the Dorena Center; support from USFS leaders to continue the program; involvement of land managers who choose to plant the resistant seedlings.
USFS and BLM staff described efforts to determine where POC grows on land under their management, the status of disease in those areas, and efforts to slow the spread of the disease, especially along roadsides and as result of timber or engineering projects. Some of this sanitation work has been funded by USFS Forest Health Protection program — not the National Forest System.
Richard Sniezko stated that the seedlings’ quantitative disease resistance means that some seedlings will die. He expects 40-50% survival of seedlings from many of the breeding zones. This is well above the level of resistance in un-improved populations.
Both BLM and the Rogue-River-Siskiyou National Forest have planted tens of thousands of resistant seedlings in recent years and plan to continue. Funding provided by COVID-19 legislation might allow increased effort. [See Dr. Sniezko’s presentation on the webinar for photos from some plantings.]
POC seedlings at Dorena; photo by Richard Sniezko
Norma Kline of the Oregon State University extension program has distributed more than 10,000 seedlings to small/non-industrial landowners. Many of the recipients shared seedlings with neighbors or are coordinating their planting over a large area. They were motivated primarily by conservation concerns. Her monitoring showed that the POC seedlings survived but did not thrive under dense tanoak canopy. They did well in competition with grass in areas near the coast where there was more moisture. They also did well under Douglasfir as long as there was dappled sunlight.
The non-governmental organization American Forests is likely to participate actively in the planting effort.
In an email to me, Dr. Sniezko asks that people who have planted POC outside its native range inform him where the tree(s) is/are thriving. This information would enhance scientists’ understanding of the species’ environmental tolerances.
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
‘Ohi‘a (Metrosideros polymorpha) is the most abundant native forest tree in Hawai`i and of enormous ecological, cultural, and economic importance. Five species of endemic Metrosideros are recognized on the Hawaiian islands. Only one — M. polymorpha — is found throughout the state. Eight varieties are recognized. These varieties inhabit different environments and have adapted to selective pressures characteristic of these locations. There are at least five other species in the Metrosideros genus, each endemic to one or a few nearby islands. Blaine et al. (2022) [full citation at end of this blog] provide a helpful summary of the tree’s ecological importance and its apparently on-going speciation.
‘Ohi‘a provides habitat for endemic birds, insects, and plants, many of which are endangered. Thus, conservation of this species — and all Hawaiian Metrosideros – is vital for the conservation of countless other taxa. In addition, high elevation ʻōhiʻa forests protect vitally important watersheds across the state. For Native Hawaiians, ʻōhiʻa is a physical manifestation of multiple Hawaiian deities so is the subject of many proverbs, chants, stories, and a foundation of scared hula. Finally, the tree is beautiful!
Native Hawaiian forests face multiple threats — invasive animals and plants, wildfire, and land-use changes. Due to such threats, natural ʻōhiʻa regeneration is largely absent in most lower-elevation forests. In this case, competition with invasive species and the presence of diseases such as ʻōhiʻa rust (Austropuccinia psidii) are probably the specific causes. Multiple government and non-governmental entities have made substantial effort to mitigate these threats.
ROD-infected ʻōhiʻa; photo by J.B. Friday
The disease Rapid ‘Ohi‘a Death (ROD) is an unprecedented threat to this species and the forests it constitutes. The disease is caused by two newly described fungal pathogens: Ceratocystis lukuohia and C. huliohia. The disease caused by C. lukuohia is more severe. To date it has been detected on the two islands farthest apart in the chain — Hawai`i (the Big Island) and Kaua‘i. C. huliohia causes a canker disease that kills trees more slowly. It is more widespread, found on Maui and O‘ahu in addition to Hawai`i and Kaua‘i. Blaine et al. (2022) and the profile here describe the two diseases’ epidemiologies, progression, impacts, and challenges.
Because of the clear threat to Hawaiian ecosystems, ecosystem services, and cultural assets, considerable effort has put into delimitation and research on possible mitigation actions since ROD was discovered in 2010. The first strategic plan covered the period 2017–2019. It focused on expanded efforts to map outbreaks, research on the epidemiology of the pathogens, and most-promising management practices. The second strategic plan covers 2020–2024. It provides for continued surveillance and improvement of these technologies; expanding outreach and public engagement; research on possible vectors of the pathogens; collection and preservation of seeds for research and future restoration; and comprehensive evaluation and development of disease resistance in ʻōhiʻa.
Soon after the causal agents were clarified, the USDA Agriculture Research Service (ARS) began screening for disease resistance. By 2016, ARS had demonstrated that five individuals from two varieties of M. polymorpha had survived inoculation by the more virulent pathogen, C. lukuohia. Their survival raised hopes that natural resistance might be present in wild populations of at least some varieties. However, more comprehensive screening of trees from throughout the species’ range is needed to provide an accurate baseline on the frequency, level, and distribution of genetic resistance to both pathogens. The goal is to produce material resistant to both pathogens that can be used to preserve the ecology, culture, and biotic communities that are dependent on this tree species.
To carry the expanded effort forward, in 2018 a collaborative partnership of state, federal, and non-profit groups was formed. Participants in the ‘Ohi‘a Disease Resistance Program (‘ODRP) include: the Akaka Foundation for Tropical Forests; USDA’s Forest Service and Agriculture Research Service; the state’s Division of Forestry and Wildlife and Agriculture Research Center; programs of the University of Hawai‘i at Manoa and at Hilo; Purdue and Arizona State universities; the Tropical Hardwood Tree Improvement and Regeneration Center; and Kalehua Seed Conservation Consulting.
Blaine et al. (2022) have now outlined a framework to guide the overall effort to identify and develop ROD resistance in M. polymorpha and, possibly, all Hawaiian Metrosideros species. The framework calls for the following activities:
(1) evaluating and operationalizing methods for inoculation-based screening and greenhouse-based production of test plants; and
(2) short-term greenhouse screenings of seedlings and rooted cuttings sampled from native Metrosideros throughout Hawai’i.
Once these tasks have been achieved, the effort is expected to expand to address:
(3) establishing field trials to validate the short-term greenhouse assays and monitor durability and stability of resistance;
drivers of susceptibility and resistance to characterize the durability and stability of genetic resistance to ROD;
(5) developing remote sensing and molecular methods to rapidly detect ROD-resistant individuals;
(6) if necessary, conducting breeding to increase the efficacy of resistance and improve durability of ROD resistance; and
(7) supporting already established and ongoing Metrosideros conservation, including state-wide seed collection and banking, with information on not only genotypes resistant to ROD but also production of ROD-resistant seed.
Blaine et al. (2022) outline how to proceed on each step, and describe the challenges that must be overcome. Challenges range from building growing and screening capacity to handle the thousands of plants required, to developing the remote sensing tools to identify diseased trees in the forest, to identifying sites for seed orchards. Actions by ‘ODRP will focus on Stage II screening in the field to examine the durability of resistance under the wide variety of ecological conditions in which ʻōhiʻa grows and in the presence of a potentially evolving pathogen. Resistance studies must expand beyond M. polymorpha varieties from only one island (the Big Island) to include the other Hawaiian Metrosideros taxa.
Once ROD-resistant M. polymorpha trees are discovered and groundwork has been laid to satisfy initial needs for resistant tree seedlings for forest restoration, scientists can begin research into the genetic basis of ROD resistance. This knowledge will assist breeding efforts which might be necessary if resistance to one of the pathogens does not confer resistance to the other, since the goal is to provide seedlings that are resistant to both.
Blaine et al. (2022) note that the state and others continue efforts to address other aspects of ROD management. These include
1) controlling the spread of the pathogen through local quarantines on movement of infected material and increased public education on bio-sanitation for forest users;
2) testing repellants to reduce beetle attack on infected trees and subsequent frass production.
3) reducing wounding of trees by fencing more pristine forests and removing feral ungulates
SOURCE
Blaine C. Luiz, Christian P. Giardina, Lisa M. Keith, Douglass F. Jacobs, Richard A. Sniezko, Marc A. Hughes, James B. Friday, Philip Cannon, Robert Hauff, Kainana Francisco, Marian M. Chau, Nicklos Dudley, Aileen Yeh, Gregory Asner, Roberta E. Martin, Ryan Perroy, Brian J. Tucker, Ale.alani Evangelista, Veronica Fernandez, Chloe Martins-Keli.iho.omalu, Kirie Santos, Rebekah Ohara. 2022. A framework for establishing a rapid ‘Ohia death resistance program. New Forests. https://doi.org/10.1007/s11056-021-09896-5
See also the video at https://www.bigislandvideonews.com/2019/06/16/video-to-save-ohia-a-genetic-resistance-program-will-be-built/
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
American beech (Fagus grandifolia) is a widespread and beautiful tree of the eastern deciduous forest. Its range reaches from Nova Scotia to eastern Wisconsin, then south to Mississippi and Louisiana and east to mid-Georgia. It is an important food source for 40 wildlife species, particularly in the northern parts of its range where few other species produce hard mast. (See Lovett et al. 2006.)
Threats
Unfortunately American beech is under threat from three non-native organisms or complexes: 1) beech bark disease, 2) beech leaf disease, and 3) beech leaf mining weevil. A fourth pest, a previously unknown – and still unnamed bark beetle in the genus Agrilus – has been detected in New York City on European beech trees. It is not yet known whether it will attack American beech and, if so, whether it will also cause serious damage (Michael Bohne, USFS, pers. comm.)
symptoms of beech bark disease; photo by Linda Haugen, USFS; via Bugwood
Beech bark disease (BBD) results from the interaction of the introduced European beech scale insect (Cryptococcus fagisuga) and several fungi in the Neonectria genus – some of which are also introduced. The resulting disease has been killing American beech trees since the beginning of the 20th Century. It has spread from Nova Scotia to much of the tree’s range. It has dramatically altered the composition and structure of stands containing beech.
symptoms of beech leaf disease; photo provided by Jennifer Koch, USFS
Beech leaf disease (BLD) was initially detected in 2012, near Cleveland. As of December, 2021, it has spread due east across New York, Pennsylvania, and New Jersey to the Atlantic, then up the coast through Connecticut and eastern Massachusetts, with a separate outbreak in central Maine. The disease is apparently associated with a nematode, Litylenchus crenatae ssp. mccanni, although additional pathogens, like bacteria, might also play a role. The origin of the North American population of the nematode is unknown; it is a related but separate subspecies from a Japanese nematode (Reed et al. 2022).
American beech defoliated by leaf mining weevil; photo courtesy of Jon Sweeney, CFS
Beech leaf mining weevil (Orchestes fagi) is, so far, limited to Nova Scotia. However, it is expected that the weevil will continue spreading throughout the range of American beech through both natural dispersal and human-assisted movement. Repeated defoliation by the weevil might increases mortality rates in forests that are surviving in the “aftermath” stage of BBD (Sweeney et al. 2020).
A new study (Reed et al. 2022) concludes that, despite being detected only 10 years ago, BLD has already become pervasive in forests surrounding Lake Erie in the U.S. and Ontario. While somewhat more prevalent in U.S. states on the eastern side of the Great Lakes (on 54% of trees) than in Ontario (on 46% of trees), BLD is spreading rapidly and affecting every canopy layer. Mortality is highest in seedlings and saplings; understory saplings die within 2 – 5 years. The occasional mortality of overstory trees occurs within seven years of [observed] infection. Defoliation and mortality of saplings allow more light to pass through to the understory; this is expected to alter plant communities on the forest floor.
Beech scale is more widespread in Ontario (found on 60% of trees) than in the U.S. (38% of trees). This is not surprising since the scale was detected in Ontario in 1960, 24 years before it was detected in portions of Ohio, New York and Pennsylvania included in the study (in 1984). Throughout this region, beech scale is disproportionately affecting overstory trees.
Only 4% of trees throughout the study area are infected with Neonectria cankers. In other words, full-scale beech bark disease is not yet widespread and is spreading surprisingly slowly. Scientists do not understand this phenomenon.
These findings are based on a network of monitoring plots a network of monitoring plots set up in 2019 set up in areas surrounding the Great Lakes. They comprise 34 plots at 17 locations in southwest Ontario and 30 plots at 25 locations in Ohio, Pennsylvania, and New York. In total the plots hold 646 live American beech trees — 412 saplings; 85 in the intermediate/suppressed (subcanopy) category; and 149 in the dominant/codominant (canopy) class.
Forest composition is similar throughout the study area. The most common species in association with American beech are sugar and red maples (Acer spp.), and white and green ash (Fraxinus spp.). Other tree species present include eastern hemlock (Tsuga canadensis), white pine (Pinus strobus), oaks (Quercus spp.), and birches (Betula spp.). Study plots had few invasive plants – although the invasive species present are well-documented to invade forests.
Ontario disease assessment
In Ontario, BLD was identified in 25 of the 34 plots. It was present on 171 saplings, 53 intermediate trees, and 70 dominant trees. Both prevalence and severity were greatest on intermediate trees. Beech scale was present at all 34 plots. While scales were found on trees of all sizes, they were almost two times more prevalent and were more severe on mature trees than saplings. Neonectria cankers were detected at 34 plots. Neonectria was rare but most severe on dominant trees. Fewer than one third of saplings and one-sixth of mature trees were pest free.
U.S. disease assessment
BLD was present in 17 of the 30 plots. It was found on 75 saplings, 30 intermediate trees, and 38 dominant trees. Saplings and dominant trees had similar levels of disease; intermediate trees had significantly less. However, BLD severity was twice as high on saplings compared to mature trees. BLD was present on more than half of the seedlings assessed – 46 out of 82. Beech scale was present in 20 of the 30 plots. It was significantly less common and severe on saplings than on mature trees. Neonectria cankers were present in only 4 of 30 plots. Canker prevalence and severity did not differ significantly among size classes.
Distribution and Effects of Beech Scale and BBD
While beech scale attack facilitates invasion by the Neonectria fungi, the disease – BBD complex – had the most limited distribution of the three pests in this study. It was found on only ~4% of beech trees throughout the study area. The disease was first reported there in the early 2000s. Although no one knows why, it has spread more slowly there than in areas to the east (Reed et al. 2022).
As is the case with beech scale, BBD disproportionately affects large diameter trees. Typically, BBD kills more than half of mature beech within 10 years of its arrival. Dying trees produce prolific root sprouts resulting in dense beech sapling understories that impede regeneration of less shade-tolerant tree species. The persistence of thickets of disease-vulnerable small beech perpetuates the disease. BBD is the only forest disease in North America that can inadvertently intensify itself by increasing densities of its host while suppressing other species.
Beech Forest Community Change in Response to Combined Impacts of BBD and BLD
It is unclear how forests will change as beech die. Some expect saplings of species already present — red maple, white ash, and, especially sugar maple — to exploit the canopy gaps. Of course, white and green ash are under attack by the emerald ash borer; DMF their ability to reach the canopy will depend on the success of biocontrol agents.
However, if BBD or BLD resistant beech survive or if BLD fails to persist, future forests might instead consist of beech thickets that would prevent all but the most shade tolerant species from establishing. Heavy deer predation on maple seedlings and saplings might also play a role. A third possibility is that morbidity from BBD and BLD might lead to uneven-aged conditions that allow younger trees — perhaps even shade intolerant species e.g., oaks — to establish.
Invasive plants also have the potential to fill gaps left by declining beech. While maple-beech forests often have sparse understories due to low understory light levels, pest-caused canopy gaps are expected to increase the abundance of invaders, especially in small woodlots and forests near urban areas. Several shade-tolerant invasive shrubs are already present in low numbers: Japanese barberry (Berberis thunbergii), tatarian honeysuckle (Lonicera tatarica), multiflora rose (Rosa multiflora), and buckthorn (Frangula sp.). Reed et al. (2022) note that these species, plus privet and autumn olive, can take advantage of small canopy gaps, especially when soils are disturbed, e.g., by active intervention to counteract the loss of beech.
Precautionary Research and Management
Reed et al. (2022) call for enhanced monitoring of beech forests focused on
the timing of BLD presence relative to tree age and size – which might affect competitiveness of sprouting beech in the understory; and
compositional and structural change in forests with BLD or to which it is likely to spread
They also recommend abandoning the management approach for BBD currently recommended by foresters. It calls for removing scale-susceptible beech so that resistant genotypes increase in prevalence. In forests with both BBD and BLD, they conclude, management of natural regeneration is unlikely to succeed because BLD will kill sprouts and saplings that might be resistant to scale. They recommend instead active management of the forest to promote mast-producing, shade intolerant species, such as oaks and hickories.
They also recommend increased support for resistance-breeding programs. Such programs already target BBD, based on the estimated 1% of American beech that show some resistance. Now those programs need to incorporate BLD resistance. (Reed et al. note that small numbers of beech show few or no BLD symptoms so might possess resistance or tolerance.)
grafted beech for resistance breeding; photo by Rachel Kappler, then USFS (now Great Lakes Basin Initiative & Holden Arboretum)
Unfortunately, the Canadian beech breeding program’s future funding is highly uncertain. To counter this threat, in part, Reed et al. (2022) suggest cryopreserving beech embryos from Canada to develop a beech conservation collection that would be available for a more robust, future Canadian breeding program. The USFS is trying to develop methods to screen trees for resistance to BLD, specifically to the nematode (J. Koch, USFS, pers. comm.)
Another approach would actively manage beech stands in which potentially BLD-resistant beech grow to help these trees reach the canopy and reproduce. In the absence of management, any BLD-resistant beech seedlings might be overtopped by faster growing, shade-intolerant species – especially if the gaps promote soil drying or sun scald.
Finally, breeding programs need to factor in the beech leaf mining weevil, DMF which — as I noted in the beginning — is spreading across Nova Scotia and could spread to the rest of the native range of beech (Sweeney et al., 2020).
The Department of Agriculture has created a website on the Department’s plant-breeding efforts. It includes a subwebsite on USFS efforts. However, I did not find much useful information there.
SOURCES
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)
Reed, S.F., D. Volk, D.K.H. Martin, C.E. Hausman, T. Macy, T. Tomon, S. Cousins. 2022. The distribution of beech leaf disease and the causal agents of beech bark disease (Cryptoccocus fagisuga, Neonectria faginata, N. ditissima) in forests surrounding Lake Erie and future implications Forest Ecology and Management 503 (2022) 119753
Sweeney J.D., Hughes, C., Zhang, H., Hillier, N.K., Morrison, A. and Johns R. (2020) Impact of the Invasive Beech Leaf-Mining Weevil, Orchestes fagi, on American Beech in Nova Scotia, Canada. Frontiers in Forests and Global Change | www.frontiersin.org 1 April 2020 | Volume 3 | Article 46
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
Asian giant hornet; photo by Yasunori Koide; Wikimedia commons
They’re still here … and perhaps more widespread than thought last year.What officials have learned is that colonies are often high up in trees, not in the ground, as expected based on behavior in Asia. This makes detection and control especially difficult.
In June a citizen found a dead Asian giant hornet (AGH) male in Snohomish County. This county in the Seattle metropolitan area is separated from Whatcom County (site of last year’s detections) by a third county, Skagit County. The Washington State Department of Agriculture (WSDA) responded by setting up traps in Snohomish and King counties, and urging citizens to be alert and report any hornet sightings.
Equally worrying, the dead wasp was determined by appearance and genetics to be unrelated to the colonies detected in 2019 and 2020 in Washington and British Columbia. Trapping in the areas found no additional specimens (S. Spichiger pers. comm.)
In July, WSDA designated the hornet genus Vespa as a quarantine pest; this action confirms WSDA authority to control access to nest sites.
nest eradication; WSDA photo
Nests Found and Destroyed
Starting in late summer, citizens began reporting sightings and officials succeeded in tracking hornets to their nests. However, it was not easy! Eradicating Asian giant hornets demands lots of resources and commitment. While all these nests were in Whatcom County – site of last year’s detections — it is clear that several colonies had been established. It seems to me highly unlikely that they have all been detected.
Detection of the first nest in 2021 came in August, following several visual detections of the hornets attacking nests of paper wasps. WSDA staff captured and tagged three hornets over a couple of days. They succeeded in tracking the third hornet when it reappeared a week later. The nest was destroyed (after removal of all hornets) on August 25th. This nest held nine layers of comb with 292 eggs, 422 larvae, and 563 prepuae. Nearly 200 adult hornets were killed. One queen was found. [Hornet Herald 21.07 Sept. 8 2021] The nest was at the base of a dead alder tree in rural Whatcom County, east of Blaine, just 400 metres south of the Canadian border.
The second and third nests were detected on September 8 and 10, 2021. In these cases, tagging and tracking the hornets was easier than in August. Nest eradication was not easy, however. Both nests were high inside dead alder trees, making access difficult. Both nests held multiple combs with hundreds of larvae, eggs, and pupae. Fortunately, only one queen was found in each. [Hornet Herald 21.08; October 5, 2021]
No detections have occurred since these.
WSDA also collected data on foraging behaviors of wasps in the third nest. Data include information on periods during the day when the wasps are active, and what materials they bring back to the nest – which includes wood pulp for nest comb construction and insect thoraces for feeding the pupae. [Hornet Herald 21.08; October 5, 2021]
It is encouraging that only one queen was found in each nest; in 2020, the single nest officials destroyed held 200 queens!
Trapping in British Columbia
Although British Columbia officials increased the number of traps in 2021, and urged citizens to also set out traps, no confirmed AGH finds were made in British Columbia until early November, when one was caught in a trap set for Japanese beetles. This hornet was on the border with Washington, so officials are trying to determine whether it came from one of the nests already discovered there.
There were a couple of unconfirmed sightings. On October 22 a single, aged specimen was found in a Japanese beetle trap about 1.2 km north of the first hornet nest extracted this year in Washington. The beetle trap had been serviced one month earlier. Canadian government entomologists are analyzing the DNA of this specimen to see if it was related to the Washington State nests.
At least one citizen said he had seen an Asian giant hornet in July, but officials said they could not investigate until they had either a picture or a specimen.
Asian giant hornet with radio tag developed by USDA APHIS scientists
Intriguing wrinkle
Mattila et al. (2021) describe an “impressive array of strategies” Asian honey bees use to protect nests from attacks by hornets in the genus Vespa, including a previously unknown use of auditory and perhaps chemical signals to warn nest mates. The authors suggest that this diverse alarm repertoire is similar to alarms issued by socially complex vertebrates such as primates and birds.
Giant hornet (Vespa soror) attacks trigger frenetic antipredator signalling in honeybee (Apis cerana) colonies. R. Soc. Open Sci. 8: 211215. https://doi.org/10.1098/rsos.211215
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 tree-killing 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
Sean Connery as Hotspur, Shakespeare Henry IV Part I (BBC, “Age of Kings”)
[Starlings – one of the agricultural pests that prompted adoption of the Lacey Act – were introduced to the U.S. because they were mentioned by Shakespeare: Hotspur says “Nay, I’ll have a starling shall be taught to speak nothing but ‘Mortimer,’ and give it him, to keep his anger still in motion.”]
Americans are increasingly aware of the damage caused by invasive species. The law that ostensibly protects our environment from most potentially invasive animals is the Lacey Act – more specifically, the “injurious wildlife” sections of the law, now known as 18 U.S.C. 42 or title 18.
When it was adopted 120 years ago, the Lacey Act was not intended to protect the environment from the full range of possible animal bioinvaders. While Congress amended it several times in the first 60 years of its existence, the law still has many gaps that impede its usefulness for that purpose.
Rep. John F. Lacey via Wikimedia Commons
When first adopted in 1900, the injurious wildlife provisions of the Lacey Act prohibited importation only of wild mammals and birds that posed a threat to agriculture and horticulture. The statute was quite broad in that it prohibited importation of any wild bird or mammal without a permit; there was no requirement that a species be designated as “injurious” to be regulated. The Act was then administered by the U.S. Department of Agriculture. [For a detailed discussion of the Lacey Act’s changing provisions, see Jewell 2020; full reference at the end of this blog.]
In 1960 the Act was amended to expand the list of taxa eligible for designation as “injurious” to include fishes, mollusks, crustaceans, reptiles, and amphibians. Congress also expanded the justifications for listing a species as injurious. It added harm to people, to forestry, or to wildlife or US wildlife resources to the law’s original concerns for agriculture and horticulture. This second change brought the purposes of the Lacey Act closer to the mandate of the U.S. Fish and Wildlife Service (USFWS) – which had assumed responsibility for implementing the Act in 1939.
Unfortunately, Congress simultaneously took other action that greatly weakened USFWS’ ability to use the Act to protect the environment from introduced animals. First, it dropped the requirement that the Secretary approve, with a permit, any importation of a wild bird or mammal.
Second, the 1960 amendment clouded the originally clear prohibition of movement of listed species across state lines. The new language prohibits “any shipment between the continental United States, the District of Columbia, Hawaii, the Commonwealth of Puerto Rico, or any possession of the United States …”
For the next 57 years, the USFWS and Congress sometimes interpreted that language as continuing to prohibit transport between the states within the continental United States. However, this situation could not last. In 2017, acting in a case that had challenged the 2012 listing of several nonnative constrictor snakes as “injurious,” the D.C. Circuit court found that the plain language of §18 U.S.C. 42(a)(1) does not prohibit the transportation of injurious wildlife between states within the continental United States. So now, transportation of injurious wildlife among the continental states is not prohibited by the statute in most circumstances.
Burmese python; photo by R. Cammauf, Everglades National Park via Flickr
The Law’s Strengths
Some aspects of the law have been strengths. Since the term “injurious” has never been defined, the USFWS has been able to use its discretion to list species that are not necessarily invasive themselves but that might cause harm in some other way. For example, the salmon family and 20 genera of salamanders have been listed because they are vectors of harmful wildlife pathogens.
In addition, USFWS has listed entire genera or families of organisms – as long as each species within the taxon has been shown to possess the “injurious” trait(s). This flexibility has probably helped listings aimed at precluding importers from switching from the species that initially raised concerns to related species.
The Law’s Inherent Weaknesses
1) Legal shortfalls
Due to the confusion created by the 1960 amendment, the USFWS now lacks authority to prohibit interstate transport of species listed as “injurious”. This gap undermines the law’s efficacy in controlling spread of listed species once they are established within the U.S.
Also, the law does not prohibit other human actions that pertain to the presence and spread of species listed as “injurious,” e.g., sale, possession, or intra-state transport. Addressing these other aspects of invasive species policy was left to other players, such as states or resource managers.
2) Funding shortfall
Neither the Executive Branch nor Congress has ever provided specific funding for implementation of the Lacey Act. Only one USFWS staffer has the job of listing species under the Act. This situation might change now, since the American Rescue Plan Act adopted in spring 2021 does provide funding over the next five years for listing species that can vector pathogens harmful to people.
Staff’s Evaluation of Its Implementation of the Lacey Act
Since USFWS took over implementation of the Lacey Act in 1939, 36 taxonomic groups have been added to the “injurious wildlife” list. Seven of these listings comprise multiple species – either as genera or families.
Two mammals have been listed since the late 1960s – brushtail possum in 2002 and raccoon dog in 1983. Recent listings have strongly focused on aquatic organisms. This is because the staff is housed in the Fish and Aquatic Conservation program and their expertise is in these species.
silver carp; photo by University of Illinois
Listing activity appeared to be building in the second decade of the 21st Century, with multi-species listings of fish, snakes, and salamanders between 2012 and 2016. However, there has been only one listing action since 2016 – and that was by an act of Congress (listing of the quagga mussel).
In two peer reviewed papers, the USFWS’ Jewell and Fuller provide a history of the Lacey Act’s injurious wildlife title and analyze the effects of listing of 307 species (those listed since 1952). They conclude that 98% of the species listings were “effective” because the listed species either had not been introduced subsequent to listing [288 species; 94% of the total number of listed species] or had not spread to additional states [12 species, 4% of the total]. Another way to calculate the latter figure is to say that 63% of all established species have remained within the state(s) where they were established at the time of listing. Only three species have been spread to additional states by human actions. In these cases, Jewell and Fuller considered the Lacey Act measures to be “ineffective”. For further details on the Jewell and Fuller evaluations of listing efficacy, see their article – full citation given at the end of this blog.
Jewell and Fuller do not evaluate the impacts of animal species introduced to the U.S. after 1960 that have never been listed under the Lacey Act, or speculate about whether listing those species might have minimized the risk of their introduction.
Jewell and Fuller consider listing of species not yet established in the U.S. to be most effective for two reasons. First, listing minimizes the probability that the species will be imported intentionally or unintentionally. Second, listing provides states with risk analyses and other information on which to rely in adopting their own restrictions, including possible prohibitions on sale or possession.
Jewell and Fuller also argue that even in the absence of legal authority to regulate interstate transport of listed species among the continental states, it is still worthwhile to list species that are already established in the U.S. They give six reasons. I summarize those reasons (placing them in my order, not Jewell and Fuller’s):
1) Listing can protect the islands of Hawai`i, Puerto Rico, and the Caribbean and Pacific territories. All are extremely vulnerable to invasive species.
2) If a species shares the traits of injuriousness with other species, particularly those in the same genus or family, then including the already-invasive species demonstrates why the related species should also be listed.
3) Many imported animals carry parasites and pathogens harmful to native species, and stopping the continued importation can reduce those threats that cause disease.
4) Prohibiting further importation of the invasive species can prevent individuals from being introduced to new areas where the species would not otherwise have arrived and can reduce propagule pressure that could introduce hardier individuals.
5) Listing can provide states and other jurisdictions with the technical information they need to pursue additional restrictions not federally authorized under 18 U.S.C. 42, such as transport into a state, possession, and sale.
6) Listing reduces propagule pressure and might enhance the efficacy of any eradication or control measures.
How to Improve the Lacey Act
1) Amend the Lacey Act to restore authority to regulate interstate movement of listed species – including among the continental states and emergency listing authority. Also establish a more streamlined listing process.
2) Strengthen implementation of the law by providing a specific, adequate appropriation to hire additional staff. Utilize the enhanced resources to assess species proactively using risk assessment tools.
It is not yet clear whether the Biden Administration will initiate a more active listing process, especially beyond the zoonotic disease vectors that are the subject of the American Rescue Plan Act.
Note: The “injurious wildlife” section of the Lacey Act (18 U.S.C. 42, or title 18) is separate from another part of the Lacey Act (16 U.S.C. 3371-3378) that is has always been more widely known. This provision regulates wildlife trafficking across State lines. It was later broadened to include plants and trafficking of wildlife and plants from foreign countries.
SOURCES
Jewell S.D. (2020) A century of injurious wildlife listing under the Lacey Act: a history. Management of Biological Invasions. Volume 11, Issue 3: 356–371, https://doi.org/10. 3391/mbi.2020.11.3.01 https://www.reabic.net/journals/mbi/2020/3/MBI_2020_Jewell.pdf
Alternative view – that Lacey Act implementation has failed to protect the U.S. – presented by the following authors:
Fowler, A.J., D.M. Lodge and J. Hsia. 2007. Failure of the Lacey Act to protect US ecosystems against animal invasions. Frontiers in Ecology and the Environment.
Springborn, M. C.M. Romagosa and R.P. Keller. 2011. The value of nonindigenous species risk assessment in international trade. Ecological Economics
Jenkins, P.T. 2012. Invasive animals and wildlife pathogens in the United States: the economic case for more risk assessments and regulation. Biological Invasions
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.
lodgepole pines killed by mountain pine beetle in British Columbia; photo courtesy of Wikipedia
Natural systems, especially forests, could provide as much as 37% of the near-term mitigation necessary to meet Paris global climate goals. In the US, conservation, restoration, and improved land management could provide carbon sequestration equivalent to an estimated 21% of current net annual emissions.
However, the current U.S. forest carbon sink, which includes soils and standing and downed wood as well as live trees, might be in jeopardy due to increasing levels of disturbance, conversion, and/or declining sequestration rates in old growth stands.
Insects and plant diseases are one such disturbance agent. Acting alone or in combination with other forest stressors, they can damage or kill large numbers of trees in short periods of time, thereby reducing carbon sequestration and increasing emissions of stored carbon through decomposition of wood in dead or injured trees.
Historically, native and introduced insects and diseases have impacted an estimated 15% of the total U.S. forest cover annually. This impact is likely to increase. One study (Feiet al., 2019) found that an estimated 41% of the live forest biomass in the contiguous U.S. could be impacted by the 15 most damaging introduced pests already established in the U.S. Continuing introductions of new pests and exacerbated effects of native pests associated with climate change portend worsening losses of live trees. These rising impact of pests, combined with more frequent and severe fires and other forest disturbances, are likely to negate efforts to improve forests’ carbon sequestration capacity.
Sources of information about introduced pests’ impacts is available from, inter alia Campbell and Schlarbaum Fading Forests II and III, Lovett et al 2016, Poland et al. 2021, many blogs on this site, and pests’ profiles posed here under “invasive species” tab. Chapter 4 of Poland et al. (2021) provides a summary of what is known about interactions between invasive species and climate change – both climate impacts on bioinvaders and bioinvaders’ effect on carbon sequestration.
The United States and other major polluting countries have certain advantages. Their strong economies have the scientific and financial resources needed to implement effective invasive species prevention and forest management strategies. At the same time, many of them receive the most new forest pests – because they are major importers. These introduced pests pose the most serious and urgent near-term ecological threat to their forests and all the ecosystem services forests provide.
So, reducing insect and disease impacts to forests can simultaneously serve several goals—carbon sequestration, biodiversity conservation, and protecting the myriad economic and societal benefits of forests. See the recent IUCN report on threatened tree species.
A Major New Study
A new study by Quirion et al. (2021) takes another step in quantifying the threat to U.S. forests’ ability to sequester carbon by analyzing data from National Forest Inventory plots. Unfortunately, the re-measurement data for the period 2001 – 2019 are not available in the NFI for the Rocky Mountain states, which represents a critical data gap in the NFI program. This gap might not have had a significant impact on the national findings, however, because while the insect damage level (measured by an earlier inventory round) was quite severe in the Rocky Mountain States, the relatively slow growth of trees in that region means carbon sequestration rates are low.
Forest stand productivity – and carbon sequestration — will typically decline immediately after pest outbreaks, then recover or even increase beyond pre-outbreak levels depending on the productivity and maximum achieved biomass of replacement plant species and related soil characteristics. However, when prevalence of the disturbance increases, by, for example, more frequent pest outbreaks, carbon stocks in standing trees and sequestration rates can be reduced for extended periods.
Findings
Nationally, insects and diseases have decreased carbon sequestration by live trees on forest land by 12.83 teragrams carbon per year. This equals ~ 9% of the contiguous states’ total annual forest carbon sequestration and equivalent to the CO2 emissions from over 10 million passenger vehicles driven for one year.
This estimate includes the impacts of both native and introduced insects and diseases, because the NFI database does not distinguish between them.
Insect-caused mortality had a larger impact than disease-caused mortality (see below). Forest plots recently impacted by insect disturbance sequestered on average 69% less carbon in live trees than plots with no recent disturbance. Plots recently impacted by disease disturbance sequestered on average 28% less carbon in live trees than plots with no recent disturbance.
Ecoprovinces in which the greatest annual reductions in live tree carbon sequestration due to pests were the Southern Rocky Mountain Steppe, Cascade Mixed Forest, Midwest Broadleaf Forest, and Laurentian Mixed Forest. (Ecoprovinces are outlined – but not named – in Quirion et al. 2021; more complete information is provided in the supplementary material.)
If this study had been carried out in the 1920’s, when chestnut blight and white pine blister rust were spreading across vast areas and killing large trees, the impact of diseases would have been much higher. Today, the most widespread impacts of diseases are on either small trees (e.g., redbay succumbing to laurel wilt) or slow-growing, high-elevation trees (e.g., whitebark and limber pine to white pine blister rust). As long as no equivalents of those earlier diseases are introduced, insects will probably continue to have the larger impacts.
western white pine killed by blister rust; photo from National Archives
Quirion et al. 2021 note that their estimates should be considered conservative. The USFS’s inventory records only major disturbances. That is, when mortality or damage is equal to or exceeds 25% of trees or 50% of an individual tree species’ count on an area of at least 0.4 ha. This criterion largely excludes less severe pest disturbances, including those from which trees recover but which might have temporary negative effects on carbon sequestration.
The study’s authors note that their work has important limitations. The dearth of data from the Rocky Mountain states is one. Other factors not considered include transfers of carbon from live biomass to dead organic matter, soils, and salvaged or preemptively harvested wood products. As trees die from pests or diseases, their carbon becomes dead wood and decays slowly, producing a lag in the carbon emissions to the atmosphere. A small fraction of the carbon in dead wood might be incorporated into soil organic matter, further delaying the emissions. A full accounting of the carbon consequences of pests and diseases would require assessment of these lags, probably through a modeling study.
affects of mountan pine beetle on lodgepole pine in Rocky Mountain National Park, Colorado photo from Wikimedia
Actions to Maintain Carbon Sequestration
Quirion et al. (2021) outline several actions that would help protect the ability of America’s forests to sequester carbon. These suggestions address both native and introduced pests, since both contribute to the threatened reduction in capacity.
Concerning native pests, the authors call for improved forest management, but warn that measures must be tailored to species and environmental context.
Concerning introduced insects and pathogens, Quirion et al. (2021) call for strengthening international trade policies and phytosanitary standards, as well as their enforcement. The focus should be on the principal pathways: wood packaging (click on “wood packaging” category for on this blog site) and imported plants (click on “plants as vectors” category for on this blog site). Specific steps to reduce the rate of introduction of wood-boring insects include enforcement to increase compliance with the international treatment standard (ISPM#15), requiring trade partners – especially those which have repeatedly shipped infested packaging – to switch to packaging made from alternative materials. Introductions via the plant trade could be reduced by requiring foreign shippers to employ integrated management and critical control point systems (per criteria set by the U.S.) and using emergency powers (e.g., NAPPRA) to further restrict imports of the plants associated with the highest pest risk, especially plant species that are congeneric with native woody plants in North America. See Lovett et al 2016; Fading Forests II & III
As backup, since even the most stringent prevention and enforcement will not eliminate all risk, the authors urge increased funding for and research into improved inspection, early detection of new outbreaks, and strategic rapid response to newly detected incursions.
To reduce impacts of pests established on the continent – both recently and years ago – they recommend increasing and stabilizing dedicated funding for classical biocontrol, research into technologies such as sterile-insect release and gene drive, and host resistance breeding.
Thinning is useful in reducing damage by native bark beetles to conifers. However, it has not been successful in controlling introduced pests for which trees do not have an evolved resistance. Indeed, preemptive harvesting of susceptible species can harm forest ecosystems directly through impacts of the harvesting operation and indirectly as individual trees that may exhibit resistance are removed, reducing the species’ ability to develop resistance over time.
Further research is needed to clarify several more issues, including whether introduced pests’ impacts are additive to, or interact with, those of native species and/or other forest stressors.
SOURCE
Quirion BR, Domke GM, Walters BF, Lovett GM, Fargione JE, Greenwood L, Serbesoff-King K, Randall JM & Fei S (2021) P&P Disturbances Correlate With Reduced Carbon Sequestration in Forests of the Contiguous US. Front. For. Glob. Change 4:716582. [Volume 4 | Article 716582] doi: 10.3389/ffgc.2021.716582
SOURCES of additional information
Campbell, F.T. and S.E. Schlarbaum. Fading Forest reports at http://treeimprovement.utk.edu/FadingForests.htm
Lovett, G.M., M. Weiss, A.M. Liebhold, T.P. Holmes, B. Leung, K.F. Lambert, D.A. Orwig, F.T. Campbell, J. Rosenthal, D.G. McCullough, R. Wildova, M.P. Ayres, C.D. Canham, D.R. Foster, S.L. Ladeau, and T. Weldy. 2016. Nonnative forest insects and pathogens in the United States: Impacts and policy options. Ecological Applications, 26(5), 2016, pp. 1437-1455
Poland, T.M., Patel-Weynand, T., Finch, D., Miniat, C. F., and Lopez, V. (Eds) (2019), Invasive Species in Forests and Grasslands of the United States: A Comprehensive Science Synthesis for the United States Forest Sector. Springer Verlag. Available for download at no cost at https://www.fs.usda.gov/treesearch/pubs/61982
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
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.
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
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 andAustropucciniapsidii.
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
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 Bretziellafagacearum) 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
Quercus lobata in Alameda County, California; photo by Belinda Lo via Flickr
Five years ago I posted a blog about the threat to oak trees from non-native insects and pathogens. I am prompted to update what I said then by the publication of a monumental new analysis of endangered oak species (Beckman et al. 2021; full citation at end of blog). This report is packed with maps and graphics displaying centers of endemism, geographic areas with highest threat levels, etc., and individual profiles of all species it deems at risk.
The new study, led by the Morton Arboretum, says there are more than 200 oak species in North America – including Mexico; but only 91 species native to the United States. Of these, 28 species qualify as “of conservation concern” – defined as facing a moderate or greater threat. The principal threats to oak species are small populations or ranges and conversion of habitats for human use. Overall, 10 (36%) of the oak species “of conservation concern” have some actual or potential exposure to established non-native pests.
The report states that two species are significantly threatened by a non-native pathogen: Shreve oak (Quercus parvula) by the sudden oak death pathogen Phytophthora ramorum and Ogelthorp oak (Q. ogelthorpensis) by the chestnut blight pathogen Cryphonectria parasitica.
Several other California oaks are under some level of attack by the polyphagous and Kuroshio shot hole borers. The goldspotted oak borer (GSOB) is mentioned only in the individual species’ profiles, and largely as a potential or undetermined threat. For example, Engelmann oak (Quercus engelmannii) is reported to have suffered some damage from GSOB but that mortality is “likely a result of a complex of factors (e.g., drought and root diseases).” The potential threat from both SOD and oak wilt is mentioned for several of the oaks that are in the red oak subgenus (Erythrobalanus).
The Morton Arboretum’s determination is based on the fact that the non-native insects and pathogens that I described five years ago are attacking primarily widespread species and have not – to date – caused sufficient damage to imperil those species. This situation contrasts sharply with certain Lauraceae (e.g., redbay) threatened by laurel wilt disease; five-needle pines killed by white pine blister rust; eastern or Canadian hemlock killed by hemlock woolly adelgid; and American beech, which now faces threats from beech bark disease, beech leaf disease, and possibly European beech leaf weevil.
Meanwhile, the non-native pests of oaks that I described five years ago continue to spread.
My Update Incorporating Morton Arboretum’s Analysis: Threats in the East
In the East (from the Atlantic Ocean to the Great Plains), oaks are under serious attack from two non-native pests; a third pest has been suppressed by biological control.
oaks killed by European gypsy moth, Shenandoah National Park; photo by F.T. Campbell
The European gypsy moth (Lymantria dispar). The APHIS quarantine map shows its spread to be largely contained. The moth is currently present throughout the Northeast as far west as Wisconsin and neighboring parts of Minnesota and Illinois; and as far south as Currituck and Dare counties in North Carolina. The European gypsy moth continues to be the target of major containment and suppression programs operated by USDA Animal and Plant Health Inspection Service (APHIS), the US Forest Service and the states. For years US Forest Service spent half of its entire budget for studying and managing non-native pests on the European gypsy moth. By FY2021, this allocation had been reduced to a quarter of the total budget. The European gypsy moth is the most widespread non-native pest (see map, linked to above) and attacks a wide range of tree and shrub species. Still, it rarely causes death of the trees.
Oak wilt (caused by the fungus Ceratocystis fagacearum) is widespread from central Pennsylvania to eastern Minnesota and across Iowa, down the Appalachians in West Virginia and North Carolina-Tennessee border, in northern Arkansas and with large areas affected in central Texas. There are several outbreaks in New York State. The most recent map I can find is from 2016 so it is difficult to assess more recent status. In that year, the US Forest Service called oak wilt one of the most serious tree diseases in the eastern U.S. It attacks primarily red oaks and live oaks. It is spread by both bark-boring beetles and root grafts.
In 2016 I also listed the winter moth (Operophtera brumata) as a threat. Now, its presence in coastal areas of New England and Nova Scotia (and British Columbia) has been reduced to almost nuisance levels by action of the biological control agent Cyzenis albicans. (See this report.)
SOD-infested rhododendron plant; photo by Indiana Department of Natural Resources
The most significant potential threat to eastern oaks identified to date is the sudden oak death (SOD) pathogen, Phytophthora ramorum. Several oak species have been shown in laboratory studies to be vulnerable to infection by this pathogen. Furthermore, the climate in extensive parts of the East is considered conducive to supporting the disease. SOD has not been established in the East. However, too frequently SOD-infected plants have been shipped to eastern nurseries, where some are sold to homeowners before regulatory officials learn about the situation and act to destroy the plants.
My Update Incorporating Morton Arboretum’s Analysis: Threats in the West
In the West, millions of oaks have been killed by several pathogens and insects that are established and spreading. Another has been introduced since my earlier blog (see Mediterranean oak beetle, below). Additional threats loom, especially Asian species of tussock moths.
Coast live oaks, canyon live oaks, California black oaks, Shreve’s oaks, and tanoaks growing in coastal forests from Monterey County north to southern Oregon that catch fog/rain are being killed by sudden oak death (SOD). In this region, SOD has killed an estimated 50 million trees. While the preponderance of dead trees are not true oaks, but tanoaks (Notholithocarpus densiflorus), significant numbers of coast live oak (Quercus agrifolia), Shreve oak (Q. parvula var. shrevei), and California black oaks (Q. kelloggii) have also been killed. SOD continues to intensify in this region, and to expand. Sixteen California counties are now infected, and the infection in Curry County, Oregon has spread farther North. More worrying, two additional strains of the pathogen have been detected in forests of the region.
The Morton Arboretum analysis singled out Q. parvula as particularly threatened by SOD. Californians note that it is the subspecies Q. parvula var. shrevei that is threatened by SOD; the other subspecies, Q. parvula var. parvula (Santa Cruz Island oak) is – so far – outside the area infested by SOD.
California black oak killed by GSOB; photo by F.T. Campbell
Also in California, coast live oaks, black oaks, and canyon oaks in the southern part of the state are being killed by goldspotted oak borer. Confirmed infestations are now in San Diego, Orange, Riverside, San Bernardino, and Los Angeles counties. See the map here. At least 100,000 black oaks have been killed in less than 20 years. Neither the State of California nor USDA APHIS has adopted regulations aimed at preventing spread of the goldspotted oak borer.
The Morton Arboretum analysis considers California black oak (Q. kellogii) to be secure.
Two more wood-boring beetles threaten oaks in southern California – the Polyphagous and Kuroshio shot hole borers. One or both of the invasive shot hole borers are known to be present in San Diego, Orange, Los Angeles, Riverside, San Bernardino, Ventura, and Santa Barbara counties. The beetles feed on coast live oaks, canyon live oaks, Engelmann oaks, and valley oaks – as well as many other kinds of trees. In the process, the beetles transmit a fungus that kills the tree. Many of the vulnerable tree species anchor the region’s riparian areas and urban plantings. See a map of the shot hole borers’ distribution here.
In November 2019, scientists discovered a new ambrosia beetle in symptomatic valley oaks (Quercus lobata) trees in Calistoga, Napa County. The insect was determined to be a European species, Xyleborus monographus. The common name is Mediterranean oak borer, or MOB. Within a few months it was known that this beetle is fairly widespread in Napa and neighboring Lake counties. The beetle had never been intercepted at ports in California or found in traps designed to detect bark beetles deployed in the San Francisco Bay area but not including Napa or Sonoma. Like other beetles in the Scolytinae subfamily, MOB can transmit fungi. One of the fungal species detected in the Calistoga infestation is Raffaelea montetyi, which is reported to be pathogenic on at least one European oak species.
The California Department of Food and Agriculture proposed assigning a pest rank to the beetle in December 2020. In their draft document ranking risk, state officials note that a proven host — Q. lobata — is widespread in California and the insect is probably capable of establishing over much of the state. The possible economic impact was described as possibly affecting production of oaks in California nurseries and triggering quarantines.
Therefore, X. monographus could exacerbate the effects of SOD on California oaks.
The Morton Arboretum has singled out Q. lobata as at risk because of conversion of more than 90% of its habitat to agriculture.
Asian gypsy moths swarm a ship in Nakhodka, Russian Far East; USDA APHIS photo
A looming potential threat to oaks on the West coast is the risk that tussock (gypsy) moths could be introduced to the area. The risk is two-fold – the Asian gypsy moth continually is carried to the area on ships bearing imports from Asia (as discussed in my blog in April). The European gypsy moth is sometimes taken across the country from its widespread introduced range in the East on travellers’ vehicles, outdoor furniture, or firewood. Both the West Coast states and USDA search vigilantly for any signs of gypsy moth arrival.
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
