The control of biological invasions in the world's oceans

The introduction of alien, or nonindigenous, animals and plants has been id entified by scientists and policy makers as a major threat to biodiversity in marine ecosystems. Although government agencies have struggled to contro l alien species on land and freshwater for decades with mixed success, the control of alien marine species is in its infancy. Prevention of introducti on and establishment must be the first priority, but many populations of al ien marine species are already well established worldwide. National and int ernational policies leave loopholes for additional invasions to occur and p rovide only general guidance on how to control alien species once they are established. ro address this issue, a multinational group of 25 scientists and attorneys convened in 1998 to examine options for controlling establish ed populations of alien marine species. The discussions resulted in a frame work for control of alien marine species to provide decision-making guidanc e to policymakers, managers, scientists, and other stakeholders. Tbe framew ork consists of seven basic steps: (1) establish the nature and magnitude o f the problem, (2) set objectives, (3) consider the full range of alternati ves, (4) determine risk, (5) reduce risk, (6) assess benefits versus risks, and (7) monitor the situation. This framework can provide guidance for con trol efforts under the existing patchwork of national laws and can help pro vide a foundation for international cooperation.