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Introduction to the Problem of
Invasive Exotic Plant Species

"An "invasive species" is defined as a species that is 1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health."

Executive Order 13112, 1999

The Problem

Invasion by exotic species has been identified second only to habitat loss as a threat to biodiversity. In addition, introduction of these species is perhaps the most permanent and unrecoverable blow to native biodiversity and ecosystem processes/integrity. Once these species are well established it is sometimes impossible to remove them. When removal is possible, it comes at a high cost financially and ecologically. Either way, the ecosystem as it was is frequently lost forever (PA Department of Conservation and Natural Resources, Invasive Species Management Plan, 2005,)

People have been moving plants, animals, and microbes around the world for centuries. Most countries, the U.S. included, now rely on plants and animals from other regions of the world for food, construction materials, ornamental plants, fiber and pets. Organisms that have been moved from their native habitat to a new location (a different ecological system other than the one in which the organism is naturally occurring) are referred to as "non-native," "non-indigenous," "exotic," or "alien" to the new environment. Most U.S. food crops and domesticated animals are non-native species and their beneficial value is obvious - for example corn, wheat and oats are examples of non-native species which are not invasive. A small percentage of exotics cause serious problems in their new environments and are collectively known as "invasive exotic species.

Definitions

Throughout this tutorial you will come across words that get used to describe invasive plants and the issues, concepts and characteristics related to these organisms. In many cases, there are several different words or terms that describe the same thing. An example is exotic. Words that you will also see being used include non-native or non-indigenous. It is important to understand that these terms mean the same thing. organisms that occur artificially in locations beyond their known historical natural ranges.

We make every effort to remain consistent with the words or terms we use to describe invasive exotic plants. At times we may use the short-cut and refer to them as invasive plants. In these cases, we are still referring to those plants that are not native to Pennsylvania and have been shown to be aggressive in displacing native species. Sources consulted for the tutorial may use other terms such as weeds, non-indigenous plants, invaders, and introduced species. Often they may be using these terms to describe invasive exotic plants, but it is possible, that these authors are not using the terms differently. Be aware of this and recognize how these terms are being used.

Native Range - Every species of plant, animal, fungi, bacteria and other organism has a home in some part of the world, where it has existed for thousands of years as a result of natural forces and influences like climate, storms, moisture, fire, soils and species interactions. Over long periods of time, these and other physical and biological factors direct the distributions of organisms in nature.

A Native (indigenous) species occurs in a particular region, ecosystem, and habitat without direct or indirect human actions (Kartesz and Morse, 1997). Species native to North America are generally recognized as those occurring on the continent prior to European settlement. Endemic is used to describe populations of native animals, plants or other organisms, that have relatively restricted distributions and are confined to certain environments.

Non-native (alien, exotic, foreign, introduced, non-indigenous) organisms are those that occur artificially in locations beyond their known historical natural ranges. Non-native can refer to species brought in from other continents, regions, ecosystems and even other habitats. Species exotic to the U.S. include those transported from Europe, Asia, Africa, South America, Australia and other parts of the world. It also includes any species moved by people from one locality in the U.S. to a new one. For example, black locust (Robinia pseudoacacia) is native to the southern Appalachian region of the eastern U.S. Because of its rapid growth and hardiness, it was planted all around the U.S. during this century for living fences, erosion control, wind breaks and other purposes. Even though it is native to the U.S., black locust is considered exotic anywhere it occurs outside its known historical natural range of southern Appalachia.

European settlers brought hundreds of plants to North America from their homelands, for food, medicinal, ornamental, and other purposes. Introductions of exotic plants continue today, and are increasing due to an exploding human population, increased international travel, and the intentional and accidental movement of large numbers of species between continents as a result of expanded international trade. Many introduced plants have become naturalized across the continent and some are replacing North American native plant species. These naturalized plants, how ever much a part of our current landscapes and ecosystems, are nonetheless exotic, since they were moved here by people rather than by natural means. Because the historical distributions of some species are unknown or unclear, research continues to attempt to unravel the tangle of human and natural influences responsible for their current ranges.

Not all exotic species are considered harmful. For example, a small number of non-invasive alien plants (e.g., corn, wheat, oats) form the basis of our agricultural industry and pose little to no threat to our natural ecosystems. However, each alien plant is one less native host plant for our native insects, vertebrates and other organisms that are dependent upon them.

The term weed is a subjective word used to describe any plant considered to be "out of place." In other words, weeds can include native and non-native plants alike, growing wherever someone wishes they weren't. Invasive exotic plants of natural ecosystems are often referred to as natural area weeds. A natural area is generally an area of land or water with predominantly native vegetation or natural geological features that is allowed to respond to the forces of nature with little to no direct human interference. The term wildlands is also used to describe these areas.

Biodiversity is, simply put, all life on earth, even that which has yet to be discovered. More specifically, it includes the millions* of diverse species, from bacteria to whales, that share the earth's lands and waters with us. Each year, many thousands of species are being extinguished as a result of human activities, such as habitat destruction and exotic species introductions.

Noxious Weed is a legal designation used specifically for plant species that have been determined to be major pests of agricultural ecosystems and are subject, by law, to certain restrictions. The U.S. Department of Agriculture regulates noxious weeds and defines them as plants or plant products that can directly or indirectly injure or cause damage to crops (including nursery stock or plant products), livestock, poultry, or other interests of agriculture, irrigation, navigation, the natural resources of the United States, the public health, or the environment. List of these weeds . Plants can also be designated as "noxious weeds" by states and counties, usually through "noxious weed boards". Pennsylvania has such a "board" and a list of noxious weeds for PA at the PA Dept. of Agriculture > Animal and Plant Health. Many noxious weeds designated for their impacts to agriculture also threaten natural areas. Melaleuca (Melaleuca quinquenervia ), a tree from Australia, aggressively invades seasonal wetlands in the Everglades National Park in Florida and has been designated a federal noxious weed. Additional listings of exotic pest plants affecting natural ecosystems are expected, as their ecological and economic impacts continue to grow.

*The actual number of species in existence is unkown and can only be estimated because we really only know about the species that botanists, entomologists and other scientists have been able to collect, process and identify to date.

Nature of Invasions

Invasive species have been introduced in a variety of ways. The means and routes by which they are introduced are called invasion "pathways." Some non-native species, intentionally introduced for beneficial purposes, later turn out to be invasive. In the U.S., examples include purple loosestrife, which is sold as an ornamental plant, as well as saltcedar which was introduced for erosion control. Many invasive species are unintentionally introduced; they move as unknown stowaways and "hitchhikers" when people and their products are transported by air, water, rail, or road. Examples of invasive species unintentionally introduced into the U.S. include chestnut blight, the naval shipworm, and imported fire ants. Chestnut blight is one of the most destructive plant diseases ever recorded. This fungus, believed to have come from Asia in imported wood, has forever changed the forest tree composition in the eastern United States. The naval shipworm was introduced into San Francisco Bay via wooden ships in the early part of the 20th century. It excavated the majority of the wood pilings, causing warehouses and loaded freight cars to fall into the Bay. Imported fire ants entered the U.S. with soil removed from ships that transported goods to the U.S. As their name suggests, they cause painful stings. Where they have established in the southern U.S., they can be found in large numbers. They can seriously injure livestock, pets, and humans. They also feed on crops and build large, hard mounds that damage farm and field machinery.

Characteristics of Invasive Exotic Plants

The most important aspect of an invasive exotic plant is how it responds to a new environment. An invasive plant displays rapid growth and spread, allowing it to establish over large areas. Free from the vast and complex array of natural controls present in their native lands, including herbivores, parasites, and diseases, invasive plants may experience rapid and unrestricted growth in new environments. Their phenomenal growth allows them to overwhelm and displace existing vegetation and form dense one-species stands (PCA - APWG, Weeds Gone Wild)

Common characteristics that invasive exotic plants tend to exhibit include:

• not being native to an area (historic records, i.e. European settlement era, do not show occurrences for the species)
• invasive tendencies in additional locations other than the area in which it is found
• ability to grow in many conditions - they are often generalists in their resource needs.
• rapid maturation
• ability to exploit and colonize disturbed ground - unlike many native plants
• ability to thrive in high nutrient conditions - this is not a natural condition in most ecosystems in our region, soils and waters typically exhibit a low nutrient condition.
• reproducing rapidly by roots and shoots. If spread by seed, produce numerous seeds that disperse and sprout easily
• having roots and rhizomes with large food reserves.
• ability to survive and reproduce under adverse conditions
• having high photosynthetic rates - "greening up" earlier in the spring than natives gives these plants an competitive advantage
• the lack of natural predators, pathogens and parasites

Impacts of Invasive Exotic Plants

Economical

Invasive species can take a heavy economic toll. Researchers at Cornell University estimate that invasive species are costing Americans approximately $137 billion every year (Pimentel et al. 2000). Even controlling a single unwanted invader can carry a price tag in the millions. The United States and Canada are spending $14 million a year just to control the sea lamprey. This species caused the collapse of the lake trout and whitefish fisheries in the Great Lakes (Wilkinson pers. comm.). In 1994, the impacts of invasive plants in the United States were estimated at $13 billion per year (Westbrooks 1998). (National Invasive Species Council, Management Plan).

In some cases, exotic plant invaders are driving our rarest species closer to extinction. According to the U.S. Fish and Wildlife Service, an estimated 42% of the nation's endangered and threatened species have declined as a result of encroaching exotic plants and animals. And management of these species is expensive. Each year, the National Park Service and the Fish and Wildlife Service spend an estimated 2 and 10 million dollars, respectively, on controlling exotic plants (Westbrooks, 1998). Invasive plants also cause great economic losses and expenditures each year, measured in billions of dollars, for agriculture, forestry, range lands and roadways management (Westbrooks 1998) (PCA - APWG, Weeds Gone Wild).

In Pennsylvania, the DCNR's Forest Pest Management (FPM) program alone is spending $400,000 of combined state and federal funds for hemlock woolly adelgid suppression on state lands in 2005. FPM spends $250,000 per year for forest pest surveys and detection on state lands. The cost of gypsy moth suppression on state lands has ranged from $500,000 to $15 million per year. A few state parks have spent between $10,000 and $30,000 per year for invasive species control. Many parks and forest districts have identified the need for additional resources to address the invasive species problems that threaten park habitats and visitor experiences, and challenge land managers' abilities to provide conservation stewardship for public lands (PA - DCNR, Invasive Species Management Plan, 2005.

Ecological

Approximately 4,000 species of exotic plants (Kartesz and Morse 1997) and 500 exotic animals (Office of Technology Assessment 1993) have established free-living populations in the United States. Nearly seven hundred are known to cause severe harm to agriculture at a cost of billions of dollars annually. Over 1,000 exotic plant species have been identified as a threat to our native flora and fauna as a result of their aggressive, invasive characteristics (PCA - APWG, Weeds Gone Wild).

The long-term effects of these changes are unknown, but the rate at which they are occurring raises real concern about the ability of native species to adapt, particularly in the face of reducing habitat availability and increasing human encroachment. Invasive plants are estimated to infest 100 million acres in the United States. Every year, they spread across three million additional acres, an area twice the size of Delaware. Every day, up to 4,600 acres of additional Federal public natural areas in the Western continental United States are negatively impacted by invasive plant species (Bureau of Land Management,1996 and National Invasive Species Council. Endangered, threatened and rare species are especially at risk because they often occur in small populations that make them particularly vulnerable.It's been estimated that approximately 42% of the imperiled species (species on the Threatened and Endangered Species list) are threatened by exotics (Wilcove, D.S., et al., 1998). This same article says that 57% of the imperiled plants are threatened by invaders, especially in Hawaii where 99% of the native plants are threatened. We have anecdotal evidence for Pennsylvania that a number of our special concern species are declining and may be lost as a result of invasive species. Recent research has shown that some invasive species can interact to cause the populations of even common species to collapse. (PA Department of Conservation and Natural Resources, Invasive Species Management Plan, 2005.

Biodiversity in Pennsylvania: Snapshot 2002 identified invasive plants as one of the leading sources of threats to Pennsylvania's natural biodiversity (Thompson, ed., 2002, www.pabiodiversity.org). The report notes that more than 37% of the current total plant species in PA are exotic or non-native. While the majority of these plants are not documented as being invasive, those such as Japanese knotweed, garlic mustard, purple loosestrife, bush honeysuckles and Japanese stiltgrass are creating serious problems for PA's native flora and fauna.

Direct impacts can come in the form of:

• changes in the availability or quantity of water or nutrients.
• displacement of native species (purple loosestrife - monopolizes wetlands once established and left unattended, thereby displacing native vegetation and the insects and birds that require those species for nesting, feeding habitat)(Other MA example, Autumn/Russian olive and honeysuckles raise nesting bird mortality due to branching structure providing less protection from predators than native shrub species).
• changes in light availability to plants in the ground layer and shrub layer or to plants and animals in lower depths of lakes and streams (ex. Bush honeysuckles - foliage grows so dense that few herbaceous species are able to survive under the shrubs).
• toxicity (ex. garlic mustard - West Virginia white - Pieris virginiensis - is a rare species of butterfly that lays eggs on native toothworts - Dentaria sp.- which are being displaced in forests where Pieris inhabits by garlic mustard. Garlic mustard has been shown to be toxic to Pieris larvae when they hatch from eggs laid on the leaves of garlic mustard, also, fewer eggs hatch on garlic mustard than on Dentaria.)
• allelopathy (when one plant produces chemicals that are toxic to other plants, an example of which is tree-of-heaven)
• reduction or elimination of localized or specialized native plant communities, such as spring ephemeral plant communities
• disruption of insect-plant associations necessary for seed dispersal of native plants
• disruption of native plant-pollinator relationships
• reduction and elimination of host plants for native insects and other wildlife
• serving as host reservoirs for plant pathogens and other organisms that can infect and damage desirable native and ornamental plants;
• replacing nutritious native plant foods with lower quality sources
• killing trees and shrubs through girdling
• increasing the incidence of plant disease and stress in forested areas
• preventing seedling establishment of native trees and shrubs

Indirect impacts to ecosystem function can come in the form of:

• changes in the hydrology of an area (ex. Tamarisk or salt cedar in western riparian areas - grows so dense that it displaces natural riparian vegetation which results in significant loads of suspended sediments and ultimate alteration in river course - increased uptake of water results in elimination of riverside wetlands.)
• changes in the rate of soil erosion (ex. Japanese knotweed - grows dense and shades out all other lower growing vegetation resulting in bare soil along river banks which erodes during seasonal flooding).
• changes in soil chemistry (ex. Japanese barberry - studies have shown that soil pH increases becoming more basic in the presence of this plant).
• changes in the frequency of wildfire -a natural process that some ecosystems depend upon. (cheat grass is an exotic grass that has invaded shrub steppe ecosystems in the intermountain west and has dramatically altered the periodicity and intensity of fire which has made survival difficult for native species not adapted to these conditions).
• changes to natural ecological processes such as plant community succession
• alterations to the frequency and intensity of natural fires
• disruption of native plant-animal associations such as pollination, seed dispersal and host-plant relationships

Genetic Dilution

• in some cases, incidence of cross-breeding with native species, alters the natives' genetic make-up. Such changes can result in the creation of a hybrid that exhibits more invasiveness than the exotic parent (termed 'hybrid vigor') or can also result in a native plants decreased ability to fight off disease, for example.. (Recent finding suggest that American bittersweet (Celastrus scandens) and Oriental bittersweet (C. orbiculatus) are crossbreeding)(Ann Rhoads, personal communication).

In summary, we consider species invasive if they demonstrate one or more of the following:

1. Alter ecosystem function (fire and water)
2. Establish in undisturbed natural areas.
3. Outcompete natives after natural disturbance
4. Prevent or depress regeneration of native species.

Disturbance Effects

Invasive species are especially problematic in areas that have been disturbed by human activities such as road building, residential development, forest clearing, logging operations, grazing, mining, ditching of marshes for mosquito control, mowing, erosion control and fire prevention and control activities. Natural disturbances, such as fires, floods, tornadoes, landslides, and tree falls also provide avenues for invasive species to get established. The enormity of change wrought upon the American landscape over the past few hundred years has thrown ecological systems out of balance and provided conditions that welcome invasion by exotic plants.

Some native plants display invasive growth tendencies in their native ranges, often as a response to natural or human-caused disturbances. For example, plants such as native grape- vines (Vitis spp.), hay-scented fern (Dennstaedia punctilobula) or New York fern (Thelypteris noveboracensis) in forests may grow vigorously in response to a tree fall or selective timber cut that opens the canopy and brings abundant sunlight into previously shaded areas. This "invasive" growth spurt is usually temporary though, and slows down again as trees and other plants fill in and the forest canopy is recovered.

The best way to reduce plant invasions is to focus on preventing non-native species introductions, managing existing infestations, minimizing disturbance to forests, wetlands, barrens and other natural communities, and learning to work with, rather than against, the natural succession of nature. (excerpted from PCA - APWG, Weeds Gone Wild)

Social

Some invasive species threaten plant, animal, and/or human health. Pathogens and parasites may themselves be invasive species or may be introduced by them (invasive vectors). Bubonic plague is perhaps history's most infamous example of a vectored disease. It was spread by non-native black rats carrying disease-infected fleas. The recently introduced West Nile virus, which is transmitted to humans by mosquitoes that feed on the blood of infected animals, currently threatens people and animals in 12 eastern states and the District of Colombia. Cholera and microorganisms that cause certain types of harmful algal blooms are moved in the ballast water carried by large ships (National Invasive Species Center, Management Plan). Giant hogweed, recently added to the PA Noxious Weed List, causes serious burns to the skin if contact with the plant is made.

In addition to these dangers, invasive species constitute a threat to our economy and quality of life. The Brookings Institution 2003 report Back to Prosperity underlines the importance of Pennsylvania's "beckoning landscapes and superb natural assets" to the future vigor of Pennsylvania's economy. Among these assets are the many opportunities for outdoor recreation in beautiful natural landscapes. Species like Japanese knotweed and mile-a-minute weed create nearly impenetrable walls of vegetation along miles of Pennsylvania's waterways. This type of infestation interferes with access to the rivers by recreational boaters, fly fishers and others, as well as completely altering the aesthetics of the area and greatly degrading the visitor experience.

In our many historic landscapes, the vegetation which one might have encountered at the time of an event or period of interest has often been replaced by recent arrivals from around the world. An historic Pennsylvania structure might now be surrounded by vegetation native not to North America, but to East Asia. Surely this is to the detriment of our shared heritage and to the quality of visitor experiences (PA Department of Conservation and Natural Resources, Invasive Species Management Plan, 2005).

The Need for Action

In many cases, invasive species cause a combination of economical, ecological and social threats. Typically, studies which document the harm caused by invasive species conclude that the U.S. needs to strengthen its legal authorities and existing programs. A 1993 report by the Office of Technology Assessment, "Harmful Non-indigenous Species in the United States," states that "Federal laws leave both obvious and subtle gaps in the regulation of harmful NIS [invasive species]" (U.S. Congress, OTA 1993). The 1999 report compiled by the National Plant Board for the Animal and Plant Health Inspection Service (APHIS), "Safeguarding American Plant Resources," notes that the laws giving the agency its authorities "were passed in response to specific plant health crises" and that "overlaps and gaps in this array of statutes often leave the Agency unsure of which authority to apply in any given case." (National Plant Board 1999). A 1996 publication by The Nature Conservancy notes that the laws that do exist often are not effective or adequately enforced (Stein and Flack 1996). A recent review by Cornell University researchers concludes, "Although [Federal] policies and practices may help reduce accidental and intentional introduction of potentially harmful exotic species [invasive species], there is a long way to go before the resources devoted to the problem are in proportion to the risks" (Pimentel et al. 2000) (National Invasive Species Center, Management Plan).

The significance of the problem has become more obvious in the past decade with the issuance of President Clinton's Executive Order 13112 in 1999. This EO resulted in the formation of the National Invasive Species Council, the increase in dedicated funding at both the state and federal level, and the formation of numerous organizations and efforts at the national, regional, state and local levels whose missions are specific to addressing the issue.

Laws and Regulations - Federal and State Responses to the Problem

There have been a number of responses in the form of legislation and regulation to the burgeoning issue of invasive species impacts. For more information on those relative to the U.S. and Pennsylvania see the section below.

Further evidence for Pennsylvania and DCNR includes an extensive in-house survey conducted by DCNR which clearly revealed that invasive species are a problem on DCNR lands. The survey also documented that the need exists for inventories, control, staff, public education, training, and resources.. In addition, a stakeholder meeting was conducted in 2004 by the DCNR - Bureau of Forestry. Participants identified invasive species as a priority issue affecting Pennsylvania's forestlands, now and in the future (PA Department of Conservation and Natural Resources, Invasive Species Management Plan, 2005).

There are a number of laws and regulations that address the control, eradication or prevention of invasive exotic plant species. New legislation or changes to current legislation have an important impact on how we, as natural lands practitioners, affect change in terms of invasive plant problems on the landscape, especially when it comes to financial resources to address these problems. Often times proposed legislation will carry with it funds for addressing invasive species. Visit the websites provided to find out more about potential funding associated with current legislation.

For the benefit of those using this tutorial, we will discuss only a few of the most pertinent pieces of legislation below. For a full review of International, National and State laws and regulations, including pending legislation, see the National Invasive Species Center website, www.invasivespeciesinfo.gov > Laws and Regulations. For more information on tools for states, including searchable database of weed laws, visit the Environmental Law Institute's website at http://www2.eli.org/research/invasives/index.cfm and review the publication "Halting the Invasion: State Tools for Invasive Species Management".

Noxious Weed Legislation - U.S. Department of Agriculture

The Federal Noxious Weed Act - Public Law 93-629 (7 U.S.C. 2801 et seq.; 88 Stat. 2148) - was enacted on January 3, 1975. This act established a Federal program to control the spread of noxious weeds.

A noxious weed is a plant or plant product that can directly or indirectly injure or cause damage to crops (including nursery stock or plant products), livestock, poultry, or other interests of agriculture, irrigation, navigation, the natural resources of the United States, the public health, or the environment.

Federal noxious weeds must also meet the definition of quarantine pest. A quarantine pest is defined by international agreement as "a pest of potential economic importance to the area endangered thereby and not yet present there, or present but not widely distributed and being officially controlled." Economic importance includes environmental impacts. State definitions vary according to the individual state laws.

The Secretary of Agriculture was given the authority to designate plants as noxious weeds by regulation, and the movement of all such weeds in interstate or foreign commerce was prohibited except under permit. The Secretary was also given authority to inspect, seize and destroy products, and to quarantine areas, if necessary to prevent the spread of such weeds. He was also authorized to cooperate with other Federal, State and local agencies, farmers associations and private individuals in measures to control, eradicate, or prevent or retard the spread of such weeds.

The federal noxious weed list can be viewed at the U.S.D.A., Natural Resource Conservation Service, PLANTS Database at http://plants.usda.gov/index.html > Invasive and Noxious > Federal Noxious Weed List.

The Plant Protection Act - Title 7 U.S.C. Chapter 104 - Plant Protection Sec. 7701. et sec. - was signed into law in 2000. It replaces the Federal Noxious Weed Act. More information on this act can be found at the U.S.D.A. Animal and Plant Health Inspection Service website, http://www.aphis.usda.gov/ppq/weeds/nwauthor.html.

Pennsylvania Noxious Weed Law

The Pennsylvania Noxious Weed Law states that it is illegal to propagate, sell or transport the following noxious weeds in the Commonwealth:

This list was initially developed to identify agricultural weeds and more recently has included weeds of natural areas. Any changes or expansions of this list requires an act of the PA Legislature.

For additional information on the PA Noxious Weed Law or Noxious Weeds, go to the PA Department of Agriculture website, http://www.agriculture.state.pa.us/ > Animal and Plant Health.

Executive Orders

Federal - Executive Order 13112

In February of 1999, President Clinton signed an executive order committing the federal government to addressing the immediate and long-term threats posed by invasive species. The order established the National Invasive Species Council which was responsible for developing a National Invasive Species Management Plan. Through the development of a National Plan and better coordination of various agencies' efforts, the EO seeks to improve existing prevention and control programs, develop new programs to address "gaps" through which invaders still enter the country, and add some new funding and other resources.

A full version of Executive Order 13112, copies of the Plan, or information about the government effort can be found at the National Invasive Species Center website, www.invasivespeciesinfo.gov.

Pennsylvania - Executive Order 2004-1

On January 27, 2004, the Governor signed an executive that established the Governor's Invasive Species Council. The purpose of the council is to advise the Governor on and direct the development and implementation of a state invasive species management plan, provide guidance on prevention, control, and rapid response initiatives and facilitate coordination among federal, regional, state, and local efforts. The council is chaired by the Secretary of Agriculture and members include heads or their designees of PA agencies responsible for the conservation of agricultural and natural resources and the protection of public health (DCNR, DEP, PAGC, PAFBC, Health, PennDOT). In addition, ten members of the public representing agriculture and natural resource organizations and educational institutions conducting invasive species research and outreach will be appointed by the governor.

The PA Invasive Species Council is in its final stages of formation with the development of a state management plan on the horizon.

For more specifics on the Executive Order and the work of the PA Invasive Species Council, go to http://www.oa.state.pa.us/oac/cwp/view.asp?A=351&Q=180946 or go to the National Invasive Species Council website, http://www.invasivespecies.gov/ > Resources.

Exotic Pest Plant Councils and Invasive Plant Councils

In response to the growing need to educate the public about the issue of invasive exotic plants, many organizations have formed. Examples of these include groups like the the Exotic Pest Plant Councils (EPPC's) and the Invasive Plant Councils (IPC's). These groups have formed at state, regional and national level. The Mid-Atlantic-EPPC is a regional organization representing the issue in Pennsylvania, Maryland, New Jersey, Delaware, West Virginia, Virginia and Washington, D.C.. As a non-profit, the group focuses on raising awareness and promoting public understanding through the development of educational tools, workshops and symposia. The MA-EPPC is a member of the National-EPPC which represents approximately 15 similar organizations on invasive plant issues of national concern.

Lists of Invasive Exotic Plants

To bring more attention to the issue and to better educate legislators, land managers, decision-makers, educators and other interested entities invasive plants are often organized in lists. There are a number of invasive plant lists that exist and include plants invasive in Pennsylvania. The purpose of each of these lists varies. Some identify federal or state regulated plants (noxious weed lists), some identify invasive plants that are problematic for agriculture and forestry while others identify invasive plants that are problematic for natural areas. Each is developed using specific criteria and processes.

Existing lists that include invasive plants of concern in PA:

The Plant Conservation Alliance, Alien Plant Working Group, Alien Plant Invaders of Natural Areas

This list of over 1,000 invasive plants is derived from a variety of sources. It is a list of invasive plants affecting natural areas throughout the U.S. (and Hawaii) and can be accessed at: http://www.nps.gov/plants/index.htm > Alien Plant Working Group > Plant Lists > Plant Lists by scientific name. Species identified as invasive in PA are identified as such

Mid-Atlantic Exotic Pest Plant Council Invasive Plant List

This list includes about 300 invasive plants that are problematic for natural areas in the Mid-Atlantic region (PA, NJ, WV, DE, VA, MD and DC). This list can be accessed at http://www.ma-eppc.org/ > Plant List. Species identified as invasive in PA are identified as such

Pennsylvania Noxious Weed List

Pennsylvania's Noxious Weed list includes species that are illegal to propagate, sell or transport in PA. The list currently includes 13 species and can be accessed at the Pennsylvania Department of Agriculture website at http://www.agriculture.state.pa.us/ > Animal and Plant Health.

DCNR Invasive Plants in Pennsylvania

This brochure, developed in 2000, includes a list of 54 species organized in three categories: most serious threats or worst offenders to PA's native ecosystems, species known to invade and are deserving of further observation, species invasive in the SE portion of PA. This list curretnly resides on the DCNR website.

As managers of natural lands, waterways and recreational amenities we are interested in invasive plants that threaten those resources in Pennsylvania. In addition, we are interested in those invasives that are established in bordering states or other places with the potential of becoming established in PA. We have developed a list of invasive plants for purposes of this tutorial that will, hopefully, be the focus of management and control efforts in PA.

Invasive Exotic Plants in Pennsylvania

This list includes 76 species of invasive exotic plants in PA. Of this, 60 have become established on natural lands and are posing a threat to native plants and animals. Sixteen species are identified under the Watch List category which means that they have been documented in a few places and are 'on the move' in the state or are significant problems in bordering states and are likely going to become problems unless prevented from becoming established in PA.

See Invasive Plants in Pennsylvania for this list.

REFERENCES:

Bureau of Land Management. 1996. Partners Against Weeds - An Action Plan for the Bureau of Land Management.

Kartesz, John, North Carolina Botanical Garden, and Larry Morse, The Nature Conservancy, 1997, Personal communication.

National Invasive Species Information Center, http://www.invasivespeciesinfo.gov

National Plant Board. 1999. Safeguarding American plant resources: A stakeholder view of the APHIS-PPQ safeguarding system. USDA-APHIS-PPQ.

Office of Technology Assessment. 1993. Harmful non-indigenous species in the United States. OTA-F-565. Government Printing Office, Washington, D.C.

PA Department of Conservation and Natural Resources, Invasive Species Management Plan, 2005, http://www.dcnr.state.pa.us/.

Pimentel, D., L. Lach, R. Zuniga, and D. Morrison. 2000. Environmental and economic costs of Non-indigenous species in the United States. BioScience 50:53-65.

Plant Conservation Alliance, Alien Plant Working Group, Weeds Gone Wild Website, http://www.nps.gov/plants/alien/index.htm.

Rhoads, Ann F. Morris Arboretum, Univ. of Pennsylvania. 2002. Personal communication.

Stein, B. and S. Flack. 1996. America's least wanted: Alien species invasions of U.S. ecosystems. The Nature Conservancy, Arlington, Virginia.

The Brookings Institution. Back to Prosperity: A Competitive Agenda for Renewing Pennsylvania. 2003. http://www.brookings.org/es/urban/publications/pa.htm.

Thompson, S., ed. 2002. Biodiversity in Pennsylvania: Snapshot 2002. Pennsylvania Biodiversity Partnership, Pittsburgh. www.pabiodiversity.org

Westbrooks, R.1998. Invasive plants, changing the landscape of America: Fact book. The Federal Interagency Committee for the Management of Noxious and Exotic Weeds (FICMNEW), Washington, D.C., p.8

Wilcove, D.S., D. Rothstein, J. Dubow, A. Phillips, E. Loses. 1998. Quantifying Threats to Imperiled Species in the United States. Bioscience. Vol. 48, No. 8 August 1998.

Wilkinson, D. 2000. Personal communication

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