Over the last few years there has been an ever increasing emphasis on invasive species. Our surroundings are changing because of them. Not only are invasive species threatening our agriculture and our forests, they are also causing major impacts to several of our major cities. Outbreaks of medfly in California and Florida have at times been widespread and costly. In New York City and Chicago, thousands of ornamental trees have been destroyed at a cost of several millions in an attempt to eradicate the Asian Long-horned beetle

So just what is an invasive species? An unofficial definition could be that an invasive species is a species that does not naturally occur in a specific area and whose introduction does or is likely to cause economic or environmental harm or harm to human health.

Official U.S. definitions regarding invasive species were provided in Executive Order 13112 signed by President William Clinton on February 3, 1999.

"Invasive species" means an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health.

"Alien species" means, with respect to a particular ecosystem, any species, including its seeds, eggs, spores, or other biological material capable of propagating that species, that is not native to that ecosystem.

"Species" means a group of organisms all of which have a high degree of physical and genetic similarity, generally interbreed only among themselves, and show persistent differences from members of allied groups of organisms.

"Ecosystem" means the complex of a community of organisms and its environment.