Echo from the end of a dolphin species

The baiji, a freshwater dolphin, has used sonar to find fish in China's Yangtze River for some 20 million years. Last week, scientists declared it basically extinct. Can the end of a nearly blind cetacean help humans see the need for greater species conservation?

Five events in Earth's history have caused extinction waves, including the asteroid thought to have slammed into the Yucatán and ended the dinosaur age. Whether the planet is on the verge of a sixth wave of extinctions, or already in it, is a matter of debate, but either way, the situation should be taken seriously.

The World Conservation Union's "Red List" is at an all-time high: 16,119 threatened species (out of 15 million estimated species). This century-old trend is largely human-made and ongoing, with one harbinger being the extinction of many large mammals from North America.

In 1973, the United States responded with the Endangered Species Act, the toughest such protection law in the world. Wolves, bald eagles, and grizzlies have rebounded, and about 85 percent of the 1,322 species on the US endangered list are stable or increasing, the Center for Biological Diversity in Tucson, Ariz., estimates.

Other places in the world are not so conservation-minded. Hot spots include Indonesia, Papua New Guinea, and Brazil, where massive logging and mining are eliminating forest habitat at alarming rates. And "China is dangerously near a crisis point" with its environment, writes Pan Yue, the vice minister of China's State Environmental Protection Administration.

What might persuade the world to make a much greater effort at species preservation?

When charismatic birds or mammals are threatened, that gets people's attention. One mammal humans warm to, the polar bear, has now been joined with another huge environmental challenge: climate change. The US Fish and Wildlife Service is to rule any day on whether to propose listing the polar bear as endangered. Environmental groups such as the Center for Biological Diversity say global warming is melting the ice on which the bears live. Climate change is likely to raise awareness about species extinction.

But what about concern for a creature as lowly as a shellfish? One way to bring remote plants and animals to the public consciousness is by connecting them with human life itself. A recent report in the journal Science had this effect when it estimated that 90 percent of the fish and shellfish species from the ocean that feed people worldwide may be gone by 2048.

A powerful moral argument can also be made: Species deserve an opportunity to survive.

Other countries are wising up to these arguments. In recent years, Canada and Australia adopted their own endangered species acts, and Malaysia is working toward one.

The difficulties, of course, occur when human needs and wants conflict directly with maintaining a healthy species habitat. Those conflicts play out in communities from the Orient to Oregon, and help explain a steep decline in the US listing of endangered species as well as pressure to reform the law. The disappearance of the baiji can sound the alarm, but humans still need to figure out exactly how to respond to it.