Aliens are on the move! They spread out underwater, smothering sea plants and destroying fish eggs in the Mediterranean Sea. They multiply and invade wooded areas in Australia and Hawaii, killing off the native flora and fauna. They travel by air, water, boateven on the shoes and clothes of humans! Award-winning science writer Mary Batten introduces young readers to the serious and ongoing environmental problems caused by invasive plant and animal species. Citing numerous examples, including the accidental release of the gypsy moth into the United States in 1869 and the deliberate introduction of rabbits to Australia by English settlers, Batten shows how in each case the delicate balance of the local ecosystem is threatened or even destroyed by the foreign intrusion. At the end of the book, Batten offers readers a glossary and a list of ideas they can use to minimize their own impact on local environments.