What is an invasive species?

An invasive species is a non-native plant, animal, or other organism (e.g., microbe) that has the ability to invade natural areas and proliferate. They will often dominate an ecosystem to the detriment, and sometimes the exclusion, of native species. As a result, invasive species are likely to cause economic or environmental problems in addition to harming human, animal, or plant health. Invasive species are able to do this because the natural conditions, predators, parasites and other organisms that keep them under control in their native range do not exist in the new environment where they have been introduced.

Learn of invasive species threatening our region.  

How do they spread?

Human activities, such as trade, travel and tourism, have increased substantially. This in turn has increased the speed and volume of species movement to unprecedented levels. Invasive species are often unintended hitchhikers on cargo and other trade conveyances. Still more species are deliberately introduced as pets, ornamental plants and food, or for recreation, pest control or other purposes.

Not all non-native species are invasive. Most experts agree that about 1/3 of the plants currently found in New York are non-native, but only a small fraction, perhaps 10 – 15%, cause enough damage to be considered invasive. The species we highlight on this website are aggressive invasive species that threaten the diversity of plants and animals as well as the quality of life in our region.

What are the costs of inaction?

On a global basis, invasive species are second only to habitat destruction as the greatest threat to native plants, animals and natural communities, such as forests, wetlands, streams, and ponds. In fact, experts estimate that invasive species have contributed to the population decline of 42% of threatened and endangered species in the U.S.

Many invasives also pose threats to agricultural areas, urban parks, yards, and roadsides. Some invasive species, suchas West Nile virus, hydrilla, zebra mussel, and emerald ash borer, prey upon, displace or otherwise harm native species.

Others compete directly with native species for nutrients, sunlight and space. Invasive species can also alter ecosystem processes, transport disease, interfere with crop production, and cause disease in animals or humans. Invasive plants are often less valuable to animals for food and shelter, so they can reduce wildlife populations.

Invasive species are a leading source of environmental and economic damage across New York State. Recent estimates conclude that invasive species cost the U.S. at least $137 billion per year. In addition to reducing the diversity of native plants and animals, plants included in this guide have the potential to impact forest regeneration, agriculture, and recreation in the Tug Hill region.

Garlic mustard, for example, has been shown to reduce the viability of tree seedlings by exuding a toxic chemical into the soil.

Japanese knotweed grows in dense patches along streams, which can alter stream habitat conditions and make fishing access difficult if not impossible.

Contact with giant hogweed can have serious health consequences.

How do we mitigate problems introduced by invasive species?

Early detection and rapid response to invasive species can prevent significant impacts to natural communities and human activities, which is why it is so important to raise awareness and enact control efforts.

New York State is being proactive about invasive species identification and control and has established Partnerships for Regional Invasives Species Management (PRISMs) throughout the state. The creation of these public-private partnerships is dramatically enhancing efforts to prevent and control the spread of invasive species. What is a PRISM?

New York State Invasive Species Task Force Report states: “By looking more at prevention, early detection, and rapid response as priorities for these funds, future invasive species problems and costs can be more effectively contained and minimized.”


Prevent the introduction of invasive species into the SLELO PRISM.

Rapidly detect new and recent invaders and eliminate all individuals within a specific area.

Share resources, including funding personnel, equipment, information, and expertise.

Collect, utilize, and share information regarding surveys, infestations, control methods, monitoring, and research.

Control invasive species infestations by using best management practices, methods and techniques to include: ERADICATION (which is to eliminate all individuals and the seed bank from an area), CONTAINMENT (which is reducing the spread of established infestations from entering an uninfested area) and SUPPRESSION which is to reduce the density but not necessarily the total infested area.

Develop and implement effective restoration methods for areas that have been degraded by invasive species and where suppression or control has taken place.

Increase public awareness and understanding of invasive species.

Develop and implement innovative technologies that help us to better understand, visualize, alleviate or manage invasive species and their impacts or that serve to strengthen ecosystem function and/or processes.

Rob Williams                              rwilliams@tnc.org                     Program Director

Megan Pistolese megan.pistolese@tnc.org
Outreach and Education

Brittney Rogers brittney.rogers@tnc.org 
Aquatic Invasive Species

Robert Smith       robert.l.smith@tnc.org 
Terrestrial Invasive Species

During this time the best way to contact our team is via email.