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The release of a non-native species into the environment could have detrimental effects on the ecosystem. The introduced species could cause damage to native populations in a number of ways: they can prey on native species, compete for their resources, mate with native species and distrupt genetic diversity, and become a pest. There are thousands of invasive species recognized in the U.S. including plants and animals.

More and more species are invading other areas of the world as a result of human mobility. Global trade, travel, exploration, and expansion have dramatically increased the number of invasions by exotic species. Some species are transported accidentally and others on purpose.

In addition to animals, plants can also be invasive. An invasive plant species is one that has become a pest, grown quickly, spreads and displaces other plants. There are some invasives that are native to Pennsylvania, however most invasive plants are non-native or exotic. This plants can invade ecosystems and outcompete the native plant community. Invasives such as Muliflora Rose, Japenese Honeysuckle, Japenese Knotweed, Purple Loosestrife, and Oriental Bittersweet are among the common invasives that cause problems for native plants. Invasives are most likely introduced to an area as a result of an individual planting them in their landscaped yard. Once they are introduced they can spread rapidly. Also, when people place their unwanted clipping and weeds from gardening into the woods, the seeds of invasives can spread quickly.

Once they spread and take over an area, invasives can change the entire dynamic of the ecosystem. Animals that rely on certain types of vegetation for survival may not be able to find food or shelter to live. Nesting sites of birds may be disturbed and water quality may be impacted by a change in stream side vegetation.

The best way to reduce the impact of both plant and animal invasive species is to limit their transport. This is a difficult task because often we don't even know how a species found its way to the new location. Also, sometimes a species will not show itself as a problem in an area until it has been present for many years. There are management techniques for controlling invasive populations. They are often very expensive and time consuming.

The best way to minimize the problem with invasives is to educate people about the effects of introducing exotic animal species and planting non-native plants in their yard. There is no legislation against invasive plants in PA because there is no way to regulate what people plant in their yard.

Brown tree snake. Courtesy of invasivespecies.org	Purple Loosestrife. Courtesy of USGS.

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