Of the 7,000 estimated non-native species present in North America, approximately 1,000 are invasive. Clearly, invasive species are in the minority, but their small numbers don't keep them from causing billions of dollars in economic and ecological harm each year. Policymakers and ecologists continue to try to figure out which species might be harmful, which invasive species are doing the most damage, and which of these might respond best to eradication efforts. Invasive species reports and case studies are prevalent in political, environmental, and scientific news cycles, and a significant portion of the public is concerned about the issue." -- publisher website