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. Invasive species can be plants, animals, and other organisms (e.g., microbes). Some invasive species, however, can be native plants that have become problems due to human activity. Human actions are the primary means of invasive species introductions. There are about 40 invasive plant species in the watershed that pose a moderate to serious threat to the environment.

On January 7, 2003, Representative Joel Hefley from CO introduced a bill in the US House of Representatives titled the "Harmful Invasive Weed Control Act". The bill is still in committee, but it would "require the Secretary of the Interior to establish a program to provide assistance through States to eligible weed management entities to control or eradicate harmful, nonnative weeds on public and private land."

The JCWP has several reccommended measures to help control invasive species.

-Educate the public on how to control invasive species, including alternative methods.

-Implement a study to identify the intensity, density, and location of invasive species in an area and how best to deal with them.

-Use the Pennsylvania Natural Diversity Inventory (PNDI) or county Natural Heritage Inventories to prioritize the most important areas to control invasive species.

-Work with foresters, biodiversity coordinator - DCNR, PGC, PFBC; help to monitor and keep track of invasive species.

-Develop plan to prevent invasive species from spreading and harming native species.

-When controlling pests, use more benign sprays such as Bt, a pest specific bacterial agent.