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Invasive Species Management Programs

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Last modified Oct 29, 2011



Experts

Dan Barringer
Natural Lands Trust
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Dan is Preserve Manager/Invasives Management Coordinator for the Natural Lands Trust.

Northeast Land Management, LLC
Northeast Land Management, LLC
717-385-5162
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Certified pesticide applicator in Pennsylvania

Michael Batcher
Michael S. Batcher, Consulting
518-686-5868
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I complete field surveys for terrestrial invasive species and provide management guidance on treatment to reduce their abundance.

Featured Library Items

Citizen’s Guide to the Control of Invasive Plants in Wetland and Riparian Areas
This booklet offers a survey of the efforts of a variety of groups that have mobilized volunteers in an effort to control invasive plants in natural areas. It is hoped that the case studies presented can provide motivation and methods for recruiting and deploying volunteers charged with the task ...

Assessment and Management of Plant Invasions
Resource managers, biologists, and all those involved in plant communities must consider ecological interactions when assessing both the effects of plant invasion and the long-term effects of management. Sections of the book cover human perceptions of invading plants, assessment of ecological int...

Weed Control Methods Handbook: Tools and Techniques for Use in Natural Areas
This handbook provides you with detailed information about the tools and techniques available for controlling invasive plants, or weeds, in natural areas. Whenever possible, language familiar to natural area managers is used, and unfamiliar terms and jargon borrowed from other fields are defined.

Biological Control of Invasive Plants in the Eastern United States
The purpose of this book is to provide a reference guide for field workers and land managers concerning the historical and current status of the biological control of invasive plant species in the eastern United States. Weeds associated with lakes, ponds and rivers (Section I); wetlands (Section ...

Mid-Atlantic Invasive Plant Council
Formerly the Mid-Atlantic Exotic Pest Plant Council, this organization coordinates regional efforts by sharing information, hosting a biennial conference, and offers a tutorial for land managers on invasive plants.

Natural Lands Trust’s Center for Conservation Landowners
Has a downloadable publication: Stewardship Handbook for Natural Lands in Southeastern Pennsylvania and case studies and resources as well as a description of planning and stewardship services offered by the Center.

Center for Invasive Species and Ecosystem Health
Host website for the WeedUS database and EDDMapS as well as Forestry Images, Integrated Pest Management Images, Forest Pests and more. Hosted by The University of Georgia Warnell School of Forestry and Natural Resources. This site also archives the Nature Conservancy’s disbanded Global Invasive S...

U.S. Fish and Wildlife Service: Invasive Species
Website with articles and resources for invasive species, including information on partnerships, grants, laws and regulations.

Invasive Plants in Pennsylvania
This website has lists of Pennsylvania invasive plants and landscaping suggestions that are alternatives to using invasive plants.

Governor’s Invasive Species Council of Pennsylvania
The PISC website covers the management plan for invasive species in Pennsylvania, agencies involved in the effort and meeting minutes for the council. It also lists invasive species known to be widespread, those of limited distribution, and those not yet found in Pennsylvania.

Plant Invaders of Mid-Atlantic Natural Areas
This illustrated handbook describes a variety of highly invasive plants impacting the region's natural areas. It provides identification tips, a few suggested native plant alternatives and some control information for a variety of invasive aquatic and terrestrial species in the mid-Atlantic region.

iMapInvasives
A consortium has formed to develop, support and maintain an on-line, GIS-based, all-taxa invasive species mapping tool, iMapInvasives, focused on serving the needs of land managers, regional planners and others working to prevent, control or manage invasive species. A particular emphasis is place...

Invasive Plant Atlas of New England
The Invasive Plant Atlas of New England’s (IPANE) mission is to create a comprehensive web-accessible database of invasive and potentially invasive plants in New England that will be continually updated by a network of professionals and trained volunteers. The database will facilitate education a...

Flora of Pennsylvania
Example of comprehensive state database of plants; where to turn to learn whether a species is native or introduced and where in the state it has been found. Also used for plant identification.

Acknowledgements

Thank you to Dan Barringer, David Steckel and Gary Gimbert from Natural Lands Trust for their expertise.

Disclaimer

Nothing contained in this or any other document available at ConservationTools.org is intended to be relied upon as legal advice. The authors disclaim any attorney-client relationship with anyone to whom this document is furnished. Nothing contained in this document is intended to be used, and cannot be used, for the purpose of (i) avoiding penalties under the Internal Revenue Code or (ii) promoting, marketing or recommending to any person any transaction or matter addressed in this document.

 

Copyright

Copyright © is held by the Pennsylvania Land Trust Association

Text may be excerpted and reproduced with acknowledgement of ConservationTools.org and the Pennsylvania Land Trust Association.

Invasive species management programs help minimize the impact of invasive species on natural lands and encourage the health of native plants and wildlife. 

Summary

Invasive species can impact the values for which land is conserved. Natural lands are not fully protected unless they also are managed for the features that first motivated preservation. Invasive species can change community structure, composition, and ecosystem processes on these lands in ways that may not be anticipated or desirable. Careful management can minimize these negative impacts.

Invasive species management programs should identify resources worth protecting and ecological threats to them. A plan should identify goals, objectives, and strategies for the land.  

The program described in the Main Description below assists landowners and land managers to develop and implement a management program for controlling invasive species. The methodology focuses on plants, but a similar approach can be used for other pest species. The techniques employed adhere to the principles of Integrated Vegetation Management (IVM). IVM practices reduce the need for pesticides, promote healthy ecosystems, and provide measurable results, such as greater natural species diversity and better control of invasive species. Management options for IVM may include biological, chemical, cultural, manual, and mechanical techniques, as well as controlled burning.

Track Record

Many land trusts such as Natural Lands Trust and The Nature Conservancy have been using the techniques described below to manage invasive plants on preserves since the 1980’s. Invasive plant management is an ongoing management tool. While there may be success in managing individual species or restoring specific sites, there will always be some invasive species present in natural areas. The goals of management should include reducing the impact of an invasive species so that a diversity of other vegetation may survive.

Typical End Users

  • Individual Landowner
  • Parks Department
  • Land Trust or Conservancy
  • Homeowners’ Association
  • Watershed Organization

Conservation Impact

  • Protects the ecological diversity of natural assets existing on a site from being replaced by a homogeneous stand of relatively few species
  • Provides examples of practices that can be implemented by landowners of both small and large tracts of land.
  • Promotes an ethic of stewardship

What You'll Need

  • Long-term commitment to ongoing stewardship
  • Expertise to identify resources and the threats to them, and the ability to prioritize by threat, by geographic site or resource being threatened, and by individual plants
  • Labor and appropriate tools and equipment to remove invasive species 

Obstacles and Challenges

  • Ongoing funding for long-term maintenance
  • Assessment and interpretation of the scale and type of work so as to achieve success and ensure public acceptance
  • Adaptability to change so that success is achieved and sustained. Scale of threat from invasive species is huge; need to have perspective that fosters sustainable action

The following case statement is used for an invasives management program for Natural Lands Trust, a regional land trust managing about 20,000 acres. It can be scaled up or down as necessary.

Program Goals

As stewards of 20,000 acres of lands protected from development, and to set a region-wide example of ecologically sound management of natural areas, the Natural Lands Trust engages in the control of invasive plants on its preserves. Lands protected from development are not “preserved” if diverse natural communities degrade over time as a result of invasion of a relatively small number of aggressive species.

The goals are to reduce the impact of invasive plants on preserves, to help other landowners manage invasive plants on their lands, and to educate the public about this environmental problem.

To accomplish these goals Natural Lands Trust land managers engage a variety of techniques to control invasive species and to manipulate habitat (such as minimizing disturbance and reducing “edge”) to favor native non-invasive species. Natural Lands Trust (NLT) is working to catalog invasive species present on its preserves and in the region, prioritize the problem species, study and standardize the best control methods, and share our experience with the public. Invasives and their management have close relationships with other NLT program areas including deer, hazard tree, and prescribed fire management.

Ecological Rationale

One of the most serious problems Natural Lands Trust and others face in the management of open space is the presence of invasive species. Vines climbing trees and exotic shrubs that choke abandoned fields have the ability to displace native vegetation, halt the natural process of succession from field to forest, and homogenize the structural and food resources of a site, thereby reducing its habitat value for native fauna. Many, but not all of the invasive species were introduced by humans from other regions of the world. After habitat loss, invasive plants and animals represent the greatest threat to endangered species.

One or more of the following characteristics may be exhibited by invasive plants—but none is necessary for invasion:  Fast seed germination, high population growth, early reproductive maturity, reproduction vegetatively as well as sexually, generalized pollination, wide tolerance to many habitat types, adaptation to disturbance, high rate of biomass accumulation, long-range seed dispersal capabilities, fruit used by wildlife (including humans), relative lack of predators or diseases in present location.

Invasive species can alter nutrient cycling, local hydrology, fire regimes, geomorphological processes (such as dune formation or stream profile), species- and structural diversity, available wildlife resources, and prevent recruitment of native species due to competition for light, nutrients, and/or moisture.

An historical land use dominated by agriculture and logging, coupled with recent development, has effectively disturbed native vegetation and added countless miles of the edge condition that is highly favorable to invasives. The misguided promotion of exotic species for erosion and livestock control, and horticulture plantings and unintentional introductions have provided seed sources to disperse numerous invasive exotic species.

Artificially high wildlife populations may further promote invasive species through soil disturbance and preferential feeding on native species. Forests that regenerated from the 90% clearcutting of Pennsylvania during the 19th century did so at a time when deer populations had also crashed. Since deer are adapted to feeding primarily on native species, there is concern that future forest succession will not be achieved given present high deer populations and the presence of so many invasive plants.

There is a higher number of invasive species being used for various purposes than ever before. The rate of species introduction is higher than in the past. The increase of invasives is exponential or logarithmic—not linear. This suggests why invasives are so much more of a problem now than when the species were first introduced—or even as recently as thirty years ago.

Natural areas are dynamic; invasive plants will always be with us. Natural Lands Trust uses a combination of strategies to minimize the impact of invasives with a minimum of effort, using natural processes such as succession and forest shade, and using native plantings to exclude invaders.

Resource Management Issues

A central issue of invasive plant management is the allocation of resources. There are more weeds  than could ever be controlled. A strategy for prioritizing problem species, and for coexisting with these plants is needed—one which will minimize their effect on the ecological integrity of a property with a minimum of effort.

In natural areas management the most efficient and effective strategy usually results from a thorough understanding of the environmental forces in the area and having management goals that work with and not against these forces. Given that growing space (light, water, nutrients, etc.) in any site is finite, successful management will be a combination of practices which make more growing space available to desirable species and less to non-desirable species—in this case, invasives.

Land managers are aware of the greatest problem species on their preserves but are not necessarily equipped to evaluate impending invasions. The vines and Norway maple and ailanthus are a known threat and we also know where the plants are located. These species we stand a chance of controlling, at least in places. Other species, such as Japanese stiltgrass and garlic mustard we can identify but are clearly beyond our means to control on a large scale. Another group of species we have yet to identify as a threat, and so we may lose the advantage of early detection and rapid response (EDRR). Part of this is unavoidable because the species has not manifested its behavior—but we can base our evaluation of threat on behavior of the species in places where it has already become established.

We prioritize a species based on the damage it can do. Since forests have been the principal vegetative form in the Eastern U.S. biome, a species that is capable of halting succession and living in the shade of an existing native woodland—such as Japanese akebia—represents the greatest threat. As the native trees die and fall, the akebia is already present, has already inhibited seedling growth. An abandoned field that fills with akebia is not likely to ever become a woods. In contrast, a plant such as Canada thistle, though it is a major pest of agricultural areas and can displace native meadow wildflowers, may represent a lower threat since it will not prevent the field in which it grow from someday becoming a forest, where it cannot grow.

We also prioritize by location. A habitat that is least impacted is where our efforts will be most successful. Working to remove invasives in the shade of a closed-canopy forest will require less effort and have a longer-lasting effect than on the highly-invaded edge of that forest, or some other manipulated landscape. Connecting forest lands and closing the canopy minimizes edge where some invasives proliferate. This technique differs from traditional wildlife management which maximizes edge; however, the traditional management evolved at a time when the threat from invasives was not widely recognized. And creation of edge favors a subset of wildlife—edge species such as deer and game birds—over the welfare of interior species and the natural ecosystem.

Resource Management Methods

Invasive plant control methods are divided into four categories:  mechanical, chemical, biological, and cultural techniques. Mechanical methods are used extensively by staff and volunteers; they include hand pulling, weed wrench, cutting (high and low, in the case of vines), mowing, digging, bush hogging, prescribed burning, brushcutting and weed whipping, and pulling with a tractor and chain or Brush Brute. These methods are effective if repeated frequently during a growing season to exhaust a plant’s root reserves, or if used in combination with other techniques.

Chemical methods involve the use of herbicides. The decision to use chemical controls is a carefully considered one. The exclusive use of herbicides alone is not likely to be an effective long-term solution for controlling invasives. Difficulties include controlling only target plants at the correct time during their life cycle, and the potential health risks to workers and the environment. Herbicides need to be applied only by trained and licensed personnel. In combination with physical methods of reducing the above-ground portion of a plant, herbicides may limit resprouting or effectively control plants when used in combination with other techniques. Typically herbicides are used in small quantities for a stump application immediately after an invasive is cut back, or they are used to control resprouts some time after the cutting.  The environmental damage from invasive plants is considered to be greater than the risk associated with the use of non-persistent herbicides.

Biological control involves the introduction of species-specific predators from a plant’s native habitat, and remains the domain of universities and government agencies. The risks associated with species introduction are high, and only well funded and thoughtfully researched programs are effective. NLT may benefit from the existence of such programs, perhaps, for example, in the case of purple loosestrife. But it does not have the resources or the mandate to undertake such research on its own. Also considered biological control is the use of grazing animals, such as goats, to control invasives such as multiflora rose.

Cultural control loosely describes changes to the structure or nutrient availability of a site to create conditions that do not favor invasive plants. This includes minimizing the edge habitats that are prone to invasion, amending soil to tie up excess nutrients, or, for example, removing multiflora rose from a habitat as a way of preventing it from serving as a ladder for vines and preventing access to control other invasive plants. Cultural methods also include replanting with a diversity of desirable species so that they can shade out invasive species.

Resource Management Equipment

Fortunately the tools used for invasives management are often the same ones that are used to maintain estate areas, trails, agricultural fields, reduce hazard trees, or meet other objectives on our preserves. These include mowers, tractors, shovels, weed whips, chainsaws, chipper, Indian tanks, brushcutters, chains, trucks, small chemical sprayers, pruners, and associated safety equipment including gloves, helmets, safety glasses, chaps, and steel-toe boots. Specialized tools include the weed wrench and the Brush Brute front-end loader attachment, two that are shared throughout our preserves.

Training is required to operate powered equipment. Volunteers are an effective means to tackle supervised labor-intensive jobs such as cutting vines with pruners and hand saws, or planting native species. Trained staff can follow up later with complementary control techniques.

Implementation

Monitor invasions and natural resources

  • Inventory, survey, and map invasive species and management efforts
  • Document in a written Invasive Plant Management Plan

Prevent new invasions

  •  Identify species known to be invasive in the region but not yet found on your land; these will be candidates for Early Detection–Rapid Response (EDRR) efforts
  • Minimize unintended mechanical disturbance
    • Minimize seed movement and species introduction 
    • Control deer population

Reduce the impact of invasive plants on the preserve

  • Prioritize management efforts
    •  by geographic location, including resources present
    • by species, including its ecological impact
    •  by individual
  • Research best management practices for control methods
  • Apply best management practices to priority sites and species using integrated vegetation management (IVM)
  • Evaluate the effect of ongoing control efforts (adaptive management)

Restore sites or promote natural succession as needed

  • Fill niches with a diversity of native vegetation

Capacity - labor (volunteer and/or paid professional staff) and equipment

  • Labor – identify, train, coordinate, and mobilize personnel appropriate to the tasks required. If entirely or partially a volunteer labor force, then a volunteer coordinator position will be necessary to ensure focused and appropriate invasive species management.
  • Equipment – Secure such tools and equipment that will ensure safe and simplest accomplishment of the scale of the tasks at hand. Purchase is preferable.

Prioritization

Prioritizing which species to control is the most important consideration; there are never sufficient resources to manage them all and there will always be external sources of weeds—so it is important to determine which species are interfering most with your goals for the land.

The Invasives Management Plan should assign a priority score to each invasive species based on its potential impact, current distribution at the preserve, the value of the habitat it invades, and the difficulty of its control—for example:

We want to prioritize species that have the capability of forming dense populations, halting succession, and/or changing soil chemistry or some other chemical or physical property of the site. We also wish to prioritize species that are just beginning to invade the preserve—those that are not already ubiquitous. Deciduous woods, the natural vegetation of the Piedmont physiographic province, is the habitat to which we assign the highest priority score. Difficulty of control is not as heavily weighted a category since management techniques and capabilities are subject to change, but we want to avoid attempting to manage invasions that are beyond our ability to control. This methodology does not necessarily capture all of the potential problem species, and does not necessarily capture trends of rapidly expanding populations. Where trade names are used, no endorsement is implied. Herbicides should be applied by trained personnel according to the directions on the container label. Natural Lands Trust, Inc. and the authors of this information are not liable for the use of management practices described in this document.

Noxious Weed Law

Only a subset of the invasive plants of natural areas—such as multifora rose, mile-a-minute, and Canada thistle—are listed under noxious weed laws. (Most are weeds of agriculture.) Enforced at the county level or by local municipality, these laws can alter which species are made priority for control on your land.

Disclaimer 

Where trade names are used, no endorsement is implied. Herbicides should be applied by trained personnel according to the directions on the container label. Natural Lands Trust, Inc. and the authors of this information are not liable for the use of management practices described in this document.

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