More than 7 billion people live on Earth today, so making sure that the planet remains habitable and hospitable for our species is of vital importance. Yet, many scientists are concerned that human activity—from water and air pollution to the emission of greenhouse gases that affect the climate—threatens the stability of the environment. This book examines differing viewpoints on how to best protect our environment and utilize the earth's natural resources. The Contemporary Issues series gives young readers a better understanding of major social issues today. Each book examines four key questions related to a controversial topic, with chapters that detail the most commonly heard arguments on both sides of the discussion. The arguments contained within are supported by data from experts as well as nonpartisan reports, allowing the reader to make his or her own informed decision on the issue.