Some areas have gone from bad to worse. This past January was the warmest on record, with an average global temperature of 54.9 degrees F (13 degrees C).

• Despite a growing consciousness of how the burning of fossil fuels contributes to global warming—raising sea levels and triggering violent weather—oil consumption increased 14 percent in the 1990s and now contributes 40 percent of all carbon dioxide released into the atmosphere each year. To complicate the problem, two-thirds of the world’s oil reserves lie in the politically unstable Persian Gulf region, which jeopardizes access.

• Drained for agriculture, development, and dams, wetlands—which help purify the air and provide wildlife habitat—have decreased by an estimated 50 percent in the past century.

• The number of large dams worldwide has increased from 5,000 in 1950 to 45,000 in 2000. These dams alter the flow of rivers, inhibit the migration of fish, and sometimes—as in the case of the Rio Grande—cause rivers to run dry in places.

• Oceans have lost 27 percent of their coral reefs in the past 50 years. Part of the problem occurs during bleaching, when increased solar radiation and warmer water causes algae inside coral polyps to be expelled. Humans play a direct role in the further destruction of coral reefs with the use of explosives and cyanide to kill and collect fish around the reefs.

• Oceans are also losing fish faster than they can be replaced. New technologies lead to overfishing and the rapid decline of populations such as bluefin tuna, groupers, and cod. Lower prices of fish at the market add to the damage by masking the short supply and preventing cutbacks in consumption.

• Finally, the problem of long-term storage for nuclear waste as well as the risk of leakage pose a threat to people across the globe. The proposed storage location at Yucca Mountain in Nevada may or may not prove effective.