In the United States, many government agencies, universities, and private firms conduct research to determine whether and where the environment is being damaged. Environmental Protection Agency experts, for example, process and scrutinize more than one hundred thousand field reports annually. Thus, many arguments about environmental harm are based on available scientific evidence.

One observer who contends that there is overwhelming proof of an ecological crisis now and in the future is U.S. vice president Al Gore, author of Earth in the Balance. Gore cites data showing dangerous levels of acid rain, global warming, and airborne and solid toxic wastes such as dioxin in North America and much of the world. He believes that nations must heed his and others’ warnings to act quickly to avert long-term environmental damage.

Others, however, assert that Gore and many environmentalists are...