Help promote new film about tree-killing pests!

A new film demonstrating the impact of non-native tree-killing insects and diseases will be shown on or around Arbor Day (April 20). You can help ensure that lots of people see the film!!! Contact the program manager at your local PBS channel to ask that the channel broadcast the film.

ash tree killed by EAB; Ann Arbor, MI; courtesy of Major Hefje
ash tree killed by EAB; Ann Arbor, MI; courtesy of Major Hefje

“Trees in Trouble: Saving America’s Urban Forests” focuses on emerald ash borer in Cincinnati. The film explores our connections to the trees and forests in our communities – and the threats to those trees. The film’s website links viewers to resources for taking action.

To see clips from the film and other resources go to this site.

The film was produced by Torrice Media. Featured experts and speakers include Prof. Dan Herms of Ohio State, Jenny Gulcik, a community forestry consultant, and Cincinnati Council member Wendell Young.
As we all know, killer pests threaten trees across the country, not just in southern Ohio! Such pests are usually introduced first in cities – not necessarily ports! – because that is where crates and pallets, imported ornamental plants, and other articles to which pests attach arrive. Furthermore, trees along streets and in yards and parks are often more vulnerable than forest trees to such introduced pests because they are often subject to other stresses such as soil compaction, air pollution, elevated temperatures, and salt exposure. Finally, city trees are often planted as multiple individuals of the same species; when a pest that attacks that species arrives, entire neighborhoods can lose their tree canopy – and the real values that canopy provides.
Because of the high value of urban trees, these pests’ greatest economic damage is in urban and suburban areas. The study by Julianne Aukema and others documented that municipalities spend more than $2 billion annually to remove trees killed by non-native pests. Homeowners spend $1 billion a year removing trees killed by non-native pests, and another $1.5 billion is lost in property values due to tree mortality.

Thus, it is vitally important that American city dwellers learn about the values that trees provide to them, the threat to those values from introduced pests, and what they can do to minimize this threat. “Trees in Trouble” is a tool to advance citizens’ understanding of these issues through a combination of broadcasts, compelling video presentations and active civic engagement efforts linked to the film.

goldspotted oak borer
goldspotted oak borer

Some people – less familiar with the issue than we are – do not immediately understand the relevance of Cincinnati’s story to other cities. We know that while the trees and killers differ across the country, the cost to the communities is the same: destruction of trees that provide shade and other important ecosystem services and create our sense of home. Plus, the ways these pests are introduced are the same – and so are the steps we can take to reduce this threat.

[The goldspotted oak borer illustrates the universality of this threat – trees in southern California are being killed, too!]
You can help overcome this roadblock!
If you would like to help promote the film to your local PBS station or to local viewers, contact Andrea Torrice at 513-751-7050 or here

If you would like to obtain a copy of the film to screen to your group, contact Andrea Torrice at the same phone number or website. (Andrea is Italian; her name is pronounced “to re chay”, with the accent on “re”.)
Aukema, J. E., B. Leung, K. Kovacs, C. Chivers, K. O. Britton, J. Englin, S. J. Frankel, R. G. Haight, T. P. Holmes, A. M. Liebhold, D. G. McCullough, and B. Von Holle. 2011. Economic Impacts of Non-Native Forest Insects in the Continental United States. Plos One 6.

Posted by Faith Campbell

Invasive plants in the West

Much of the attention to invasive plants has focused on herbaceous plants (forbs and grasses) invading grasslands and sagebrush steppes of the West. Certainly these plants have invaded large areas and have – in the case of “strong” invaders – caused significant changes not just in plant community composition but also to food webs and even ecosystem structure and function. Some of these invaders have imposed large costs by reducing livestock forage, fueling more frequent fires, or contributing to severe declines in populations of iconic wildlife species.
For these reasons, the House Interior and Oversight committees have held several hearings on invasive species in recent years. Much of the committees’ focus has been on invasive plants and the failure of federal land-managing agencies to curtail or reverse their spread.

Scotch broom

Scotch broom; photo by Eric Cooms, Oregon Department of Agriculture

At the most recent hearing, Dr. George Beck of Colorado State University noted that the number of acres of land managed by the Bureau of Land Management that has been invaded by harmful non-native plants has doubled since 2009, reaching 77 million acres. Dr. Beck and his allies in the Healthy Habitats Coalition (HHC) believe that federal agencies could bring about a decline in the “weed”-infested area if they focused their resources. The HHC has persuaded members of Congress and Senators to introduce two bills (H.R 1485 & S. 2240) which would, inter alia, require land-managing agencies to allocate their invasive species funds according to the following formula: 75% for on-the-ground activity; 15% for combined research and outreach; 10% or less for administrative costs. (I discussed these proposals in my blog of January 4th.) The HHC apparently has given up trying to persuade the Congress to increase funding for land managing agencies’ resource management programs; instead, they seek to re-direct existing (shrinking) agency funds away from environmental compliance, planning, priority-setting, and research and to “on-the-ground” actions.

But I don’t think reversing plant invasions should be tackled without science and planning.

The remainder of this blog is based on the research results of Dean Pearson, USFS researcher based in Montana. See particularly the three sources listed at the end of the blog.

Studies have shown that simply suppressing the target weed does not ensure mitigation of its impacts. Managers need to weigh the success of control measures against their side effects. In the end, it is often very difficult if not  impossible to restore invaded ecosystems to their pre-invasion condition. Instead, the goal of “weed” management should be to improve the system as a whole, as measured by the overall system response to management and not simply by the degree to which the target weed is suppressed. Pearson calls this “directed community assembly”.
Acting otherwise – wasting limited funds and resources on programs that don’t succeed; or – worse – that result in exacerbated ecological damage – is not acceptable! Nor is it acceptable – in my view – to be so focused on providing forage for livestock as to ignore invader- or management- induced decimation of native forbs (see below).

Pearson’s studies have focused on efforts to suppress spotted knapweed, one of the worst invaders in the grasslands of the intermountain West. Spotted knapweed invasions have both direct and indirect effects on these systems, including replacing the principal native forb (arrowleaf balsamroot); causing significant declines in invertebrates such as grasshoppers that are fed on by many small predators such as birds, small mammals, and spiders; and probably  decreasing forage for domestic and wild ungulates. Invasive European forbs (including spotted knapweed) are generally larger, more rigid, and more structurally complex than the native grassland vegetation. This shift in vegetation architecture has led to a dramatic increase in native web-building spiders, resulting in an astonishing 89-fold increase in predation rates on spider prey. Knapweed invasions also apparently increase soil erosion and change the availability of soil nutrients. So, knapweed invasions have significant and persistent ecological effects. The variety of effects means that controlling spotted knapweed is likely to restore pre-invasion conditions only to the extent that native vegetation recovers. Recovery of the plant community might in turn depend on the ability to mitigate abiotic impacts of invasion, restore seed sources, and address similar factors that may interfere with native plant recovery.
Addressing the complexity of natural systems’ responses to plant invasion is difficult, especially given the limitations of available management tools.

According to USFS researchers Dean Pearson and Yvette Ortega, to improve weed management in natural systems, we need to better understand three important factors that greatly complicate natural areas weed management. Managers need to:
1) determine the invasive plants’ impacts on species, community, and systems; and which ones may be amenable to mitigation given current tools.
2) understand how prospective management tools might cause deleterious side effects and what can be done to minimize those effects.
3) understand the ecological conditions and processes underlying secondary weed invasions so that they can develop strategies to reduce the risk of secondary invasion following target invader suppression. (Pearson & Ortega 2009)

Programs aimed at countering plant invasions – no matter the method used – can cause unwanted damage to the ecosystem (= side effects). Side effects might affect not just non-target native plants, but also higher trophic levels, community interactions, and even ecological processes structuring the system.
These side effects need to be balanced against the damage caused by the invasive plants due to the complexity of natural systems and the limited specificity of the tools employed. Some might persist for years after control of the invasive plant. Managers need to consider the effects of both the invasive plants and the management action when selecting a strategy.

Forbs commonly making up ~80% of species richness in the intermountain meadows. In some un-invaded plots in western Montana, arrowleaf balsamroot mean cover was twice that of the native grass bluebunch wheatgrass. Forbs support communities of pollinators, herbivores, and higher trophic levels. Both invasion by alien forbs such as spotted knapweed and weed control efforts using either herbicides or grazing can lead to suppression of the native forbs. Thus at the study sites, broadcast spraying of the herbicide picloram reduced arrowleaf balsamroot cover and fecundity variables by nearly 60%. In this case, knapweed control efforts actually exaggerated the trajectory of species composition change initiated by spotted knapweed invasion – even when the invader was successfully removed.
Biological control is the most selective weed management tool currently in use other than hand pulling. However, even highly host-specific biocontrol agents can have rather significant non-target effects. One example is the dramatic increase in deer mouse populations in areas where they can feed on gallflies introduced as biocontrols for knapweed. Deer mice support the hantavirus pathogen, so this represents a potential human health threat. Worst of all, the gallflies have not proved effective at reducing knapweed populations – so the invasive plant, the mice, and the virus now all thrive. (In cases when the biocontrol agent is efficacious in significantly reducing the target plant species, any undesirable side effects will also be reduced.)
Furthermore, success in suppressing invasion by one set of plants often facilitates invasion by some other plant species that might cause greater changes to the system or that are harder to control. The problem of secondary invaders is not limited to any one management strategy, target weed, or secondary invader. Pearson think secondary invasion is likely any time additional species of strong invaders are present at a site where a dominant weed is controlled and the secondary invader proves relatively insensitive to the control method.

Grasses are most often the secondary invaders (whereas most target weeds were forbs). Perhaps, at least in some cases, weed control is simply accelerating general patterns of invader succession. In their study area in western Montana, Pearson and Ortega have found that cheatgrass invasion occurred faster in herbicide treated areas, but it also occurred in both otherwise un-invaded native grasslands and untreated spotted knapweed-invaded sites.
Secondary invasion by cheatgrass might be a particularly common consequence of weed control measures in western North America, given the species’ widespread occurrence, and its ability to exploit resources released by suppression of perennial taxa, outcompete native grasses, and attain dominance even when present at low initial densities (Ortega and Pearson 2010).

Pearson calls for understanding and addressing the system-level processes such as propagule pressure or disturbance underlying and promoting invasions in order to minimize secondary invasions.

In some cases, full restoration is not the manager’s goal. Managers of areas managed primarily as grazing lands might accept loss of forbs; even cheatgrass can be used as forage during part of the year. However, large scale reductions of forb diversity in grassland systems would not be acceptable in natural areas management.

While I think highly of Dr. Pearson’s studies, I think that researchers in the West pay too little attention to the contributing role of propagule availability, especially people’s role in taking propagules to sites where they can initiate invasions. Human movement of plants to satisfy wants for ornamental horticulture, or as unwise choices for erosion control or wildlife forage and shelter plants explains numerous examples of invasive forbs, shrubs, and trees proliferating across the West. However, there are also recent examples of unwise propagation of livestock forage grasses – cold-tolerant buffelgrass, anyone?
Sources of scientific evaluations of plant management strengths and difficulties:

Yvette K. Ortega and Dean E. Pearson. 2010. Effects of Picloram Application on Community Dominants Vary With Initial Levels of Spotted Knapweed (Centaurea stoebe) Invasion. Invasive Plant Science and Management 2010 3:70–80

Pearson, D. E. and Y. K. Ortega. 2009. Managing invasive plants in natural areas: moving beyond weed control, pp 1-21, in (ed.) R.V. Kingley, Weeds: Management, Economic Impacts and Biology. Nova Publishers, NY

Ortega, Y. K., and D. E. Pearson. 2005. Strong versus weak invaders of natural plant communities: assessing invasibility and impact. Ecological Applications 15:651-661.

Posted by Faith Campbell

Invasive plants – huge numbers, continuing introductions & spread …

The U.S. is badly invaded by non-native plants. In the database he maintains,
Rod Randall of Western Australia reports that more than 9,700 non-native plant species are naturalized in the U.S. In this compendium, Randall defines “naturalized” species as those having self-sustaining and spreading populations with no human assistance. Not all of these species impact upon the environment.

RRandall W H

As noted, not all 9,700 species are “invasive”. It is likely that a significant proportion of the invaders are “weak” invaders which coexist with the native plants and make up minor components of the plant community. Others are “strong” invaders that can rapidly attain community dominance and dramatically impact native species and ecological processes (Ortega and Pearson 2005).

But the evidence is that the situation will grow worse. A study of a small proportion of the naturalized plants (1201 alien species; 755 invasive; Bradley, Early & Sorte 2015) found that
– Invasive and alien plants are more widely distributed than natives across the continental United States
– The average invasive plant now inhabits only ~ 50% of its expected range
– Biological factors are less important than human actions in facilitating spread

According to Dr. George Beck of Colorado State University, by 2015, the acreage of land managed by the BLM that is invaded by non-native plants exceeds 77 million acres – more than twice the areas reported in 2009 (35 million acres) (see Dr. Beck’s testimony here). I noted in my blog about threats to U.S. National parks that are World Heritage sites (October 21, 2015), National parks from Hawai`i to Florida have been badly damaged by invasive plants.

Another source reports that more than 500 plant species invasive in some region are being sold on-line globally (Humair et al. 2015).

USDA APHIS has adopted a pre-import risk-screening system. Based on these analyses, utilizing the NAPPRA process, in April 2013 APHIS determined that 41 plant species may not be imported until a risk assessment has been conducted because of the risk they pose of being invasive. APHIS proposed a second group of species, containing 22 species, in May 2013. However, this list has not been finalized two and a half years later – despite meeting with conservation organizations/stakeholders in April 2015 at which we discussed ways to speed up the approval process. (We were told that the delay is caused by controversy over taxa proposed for NAPPRA-listing because their link to plant pests; that there is no controversy over the taxa to be restricted as potentially invasive plants.)


Clearly the threat from invasive plants is great and growing. The U.S. Department of Agriculture needs to adopt procedures that enable APHIS to act more quickly to curtail introduction and human-assisted spread of invasive plants. APHIS and federal land-managing agencies need adequate resources to develop and apply effective and environmentally sound control measures.

Bradley, B.A., R. Early & C. J. B. Sorte. 2015. Space to invade? Comparative range infilling and potential range of invasive and native plants. Global Ecology and Biogeography

Humair, F., Humair, L., Kuhn, F. and Kueffer, C. (2015), E-commerce trade in invasive plants. Conservation Biology, 29: 1658–1665. doi: 10.1111/cobi.12579
Ortega, Y. K. and D. E. Pearson. 2005. Strong versus weak invaders of natural plant communities: assessing invasibility and impact. Ecol. Appl. 15:651–661


posted by Faith Campbell

Fed up by lack of action on invasive species? Let’s pressure the right targets!

CapitolOn December 1, the House Oversight Committee, Subcommittee on Interior, held a hearing on invasive species. This hearing was apparently held at the request of the ranking Democrat, Brenda Lawrence of Michigan. Ms Lawrence is most concerned about aquatic invaders in the Great Lakes. Chairwoman Cynthia Lummis is from Wyoming, so her focus is on invasive plants on western rangelands.
Chair Lummis opened the hearing, but left promptly. Other subcommittee members who were present for varying lengths of time were Paul Gosar (R-AZ), Ken Buck (R-CO), Gary Palmer (R-AL), Brenda Lawrence (D-MI), and Stacey Plasket (D-USVI) ; from full committee: Will Hurd (R-TX).

The witnesses were the newly appointed executive director of the National Invasive Species Council (NISC), Jamie Reaser; the president of the Reduce Risk from Invasive Species Coalition (RRISC), Scott Cameron; Dr. George Beck of Colorado State University, representing the Healthy Habitats Coalition (HHC); and Dr. Alan Steinman, expert on aquatic invaders from Grand Valley State University in Michigan.
This hearing followed those in past years that had been stimulated by the HHC. Both HHC and Congressional members expressed great frustration that the federal government is not putting sufficient effort into stopping or reversing the spread of invasive plants on western rangelands.
The December hearing – like its predecessors – focused the criticism on NISC. I think this focus is misguided. NISC has no independent authority or power; it was created to coordinate agencies’ actions, not to substitute for them. Its staff lack sufficient rank to tell agencies what to do.
In § 4 of Executive Order 13112, NISC’s duties are listed as providing national leadership through (a) overseeing implementation of this order, seeing that Federal agencies’ activities are coordinated, complementary, cost-efficient, and effective, …; (b) encouraging planning and action at local, tribal, State, regional, and ecosystem-based levels …; (c) developing recommendations for international cooperation …; (d) developing, in consultation with the Council on Environmental Quality, guidance to Federal agencies pursuant to the National Environmental Policy Act (NEPA)…; (e) facilitating development of a coordinated network among Federal agencies to document, evaluate, and monitor IAS impacts …; (f) facilitating establishment of an … information-sharing system …; and (g) preparing a national Invasive Species Management Plan every two years.
NISC has fallen far short of these requirements. It has not succeeded in developing guidance on NEPA – at least in part because CEQ has not cooperated. Most glaringly, NISC has issued only two Management Plans over 15 years — the most recent in 2009. All Members at the hearing complained to Reaser about this failure. Members see the Plan as key to setting priorities and ensuring that funds are well-spent.

All Members seemed to think that NISC actually should carry out on-the-ground activities and direct agencies’ priorities. Some want NISC to overcome federal agencies’ alleged foot-dragging in helping local groups eager to attack local problems, or to pressure Native American tribes to cooperate.

While I share the critics’ frustration about federal agencies’ inaction, I believe the productive approach is to apply pressure on – and where deserved, support for – those who have the authority and power to act, but who often choose not to. VilsackThese are:
• heads of agencies and departments, especially the secretaries of Agriculture and Interior and their Under and Assistant secretaries;
• the President;
• budget staffs of these and other relevant agencies;
• the Office of Management and Budget;
• Members of the Congressional appropriations committees.

If these people think that dealing with invasive species is politically important, they will do so. If they don’t hear from their constituents about invasive species, they will focus on other issues.

At the hearing, Scott Cameron, of RRISC, said that what is missing is commitment at the Assistant/Under Secretary Level. Such a commitment would both drive coordination among agencies at headquarters and provide “cover” for regional staff trying to work together. He feels that a new Management Plan is useful but not sufficient. Scott made several recommendations intended to raise the political visibility of invasive species issues:
1) NISC submit annual work plan to Congress – he thought this would get political level attention in the departments;
2) NISC serve as forum to coordinate with regional governors’ associations;
3) NISC create national network of regional early detection/rapid response efforts;
4) NISC serve as forum for regional officials of land-managing agencies to coordinate and work together – this might succeed in getting attention of agency leadership and OMB;
5) NISC ensure coordination of priorities and approaches by member agencies at headquarters level; and
6) NISC evaluate best practices by other governments, propose their adoption by the United States.

Dr. Beck, of HHC, reiterated his constituency’s complaint that there has been little progress on invasive species problems despite three decades of effort. He blamed the lack of leadership by NISC – without saying how staff can “lead” the political appointees who head agencies! He called – again – for abolition of NISC and transfer of its $1 million budget to “on the ground” programs. Beck also decried inconsistencies in agencies’ budgets, lack of collaboration with states and local groups in setting priorities, and NEPA having become an excuse to avoid taking action.

HHC has promoted introduction of bills in both the House and Senate – H.R 1485 & S. 2240 – which would require:
• strategic planning;
• cooperation with states;
• categorical exclusion from NEPA review for efforts to protect high-priority sites;
• 5% annual reduction in weed species’ extent; and
• allocation of agencies’ invasive species funds according to the following formula: 75% for on-the-ground activity; 15% for combined research and outreach; 10% or less for administrative costs.

Of these recommendations, I think the proposed dropping of environment reviews of invasive species management programs – especially in “high priority” sites of high ecosystem values – would be a disaster. Management programs have environmental impacts, too; and some approaches cause more harm than good. For example, use of herbicides to eliminate knapweeds has sometimes resulted in takeover of the site by non-native annual grasses that are even more difficult to control.

EAB profile reverse

Also, I think the proposed funding allocation is very unwise. Research and outreach often contribute enormously to control or containment of invasive species. I have been unable to get straight answers from the USDA Forest Service about how such an allocation would affect their programs – which are divided among three separate entities – Research, State and Private Forestry, and National Forest System.

HHC is very active in promoting its position – and those of us who think differently are not yet being heard in Congress.

I think there is room to work with members of the House Oversight Committee to focus more attention on the agencies’ political leadership – where it belongs and where pressure might have an effect. Rep. Lawrence seems interested in continuing efforts. Rep. Hurd of Texas asked about steps to prevent plant pest introductions (none of the witnesses knew about APHIS programs). Furthermore, a second Michigander, Rep. Dan Benisheck, and a Californian, Rep. Mike Thompson, co-chair the Invasive Species Caucus. Although none of them has yet expressed concern about tree-killing pests, given where they are from they might be persuaded to engage.

At present, the only Congressional champion for effective invasive species programs – especially as regards tree-killing pests – is Senator Leahy of Vermont. He has helped prevent further cuts in budgets for APHIS and USFS. We need more friends in Congress.

I urge you – and your friends! – to contact your Representatives and Senators to explain how invasive species are damaging important ecological and economic resources in your state. Ask them to work with their colleagues to support and improve federal programs aimed at preventing new introductions, containing species already introduced, and developing effective methods to reduce pests’ impacts and restore native forests.

Posted by Faith Campbell