INTRODUCED SPECIES - A SIGNIFICANT COMPONENT OF HUMAN-CAUSED GLOBAL CHANGE

Biological invasions are a widespread and significant component of hum an-caused global environmental change. The extent of invasions of ocea nic islands, and their consequences for native biological diversity, h ave long been recognized. However, invasions of continental regions al so are substantial. For example, more than 2,000 species of alien plan ts are established in the continental United States. These invasions r epresent a human-caused breakdown of the regional distinctiveness of E arth's flora and fauna - a substantial global change in and of itself. Moreover, there are well-documented examples of invading species that degrade human health and wealth, alter the structure and functioning of otherwise undisturbed ecosystems, and/or threaten native biological diversity. Invasions also interact synergistically with other compone nts of global change. notably land use change. People and institutions working to understand, prevent, and control invasions are carrying ou t some of the most important - and potentially most effective - work o n global environmental change.