Aliens live among us. Thousands of species of nonnative flora and fauna have taken up residence within U.S. borders. Our lawns sprout African grasses, our roadsides flower with European weeds, and our homes harbor Asian, European, and African pests. Misguided enthusiasts deliberately introduced carp, kudzu, and starlings. And the American cowboy spread such alien life forms as cows, horses, tumbleweed, and anthrax, supplanting and supplementing the often unexpected ways "Native" Americans influenced the environment. Aliens in the Backyard recounts the origins and impacts of these and other...