"Did you know that brown rats were brought to the United States in the eighteenth century on a ship from England? Or that thousands of exotic pets were released into the Florida Everglades after a hurricane in 1992, leading to today's booming Burmese python population? All over the country, non-native species from around the world have been introduced to our lands, irrevocably changing the natural balances of their new habitats. This is the story of some of those newcomers, but also of human error and nature gone wild. By looking at thirty different intrusive plants and animals, They Are Here! explores invasive species, their impact on our environment, and the steps we can take to support local ecosystems under threat."--Provided by publisher.