Hainan gibbons sing to each other every morning, but these days they do not have much to sing about.
The species is native to a Chinese island that is not only a fruitful producer of rice and rubber but also a golfer's paradise. Most of its forests have been destroyed to accommodate these activities, and the gibbon population is down to a couple of dozen. If the species disappears, it will be the first ape to go extinct since the beginning of the Holocene era 12,000 years ago.
The Hainan gibbon is only one of 4,224 species listed as critically endangered by the International Union for the Conservation of Nature. Attention tends to focus on mammals and birds, but amphibians such as frogs are even more at risk.
In the course of the past few centuries, mankind's economic growth has caused many of the problems that other species face. However, greater human prosperity now offers other species their best chance of hanging on.
There have been five great extinctions in the history of Earth. One killed off the dinosaurs, another wiped out as much as 96 percent of species on Earth. All probably were caused by geological events or asteroids. Many scientists think that a sixth is under way, this one caused by man.
From the time that he first sharpened a spear, technological progress and economic growth have allowed man to dominate the planet. He is reckoned to be responsible for wiping out much of the megafauna — giant elk, aurochs, marsupial lions — that once populated Earth. When he paddled across the Pacific, he exterminated 50 percent to 90 percent of the bird life on the islands he colonized. Technology allowed him to kill creatures and chop down forests more efficiently and to produce enough food to sustain 7 billion people. As a result, during the past few centuries, extinctions are thought to have been running at around 100 times the rate they would average in his absence.
When people start to reach middle-income level, however, other species start to benefit. That is partly because, as people get richer, their interests begin to extend beyond necessities toward luxuries. For some people that means expensive shoes, for others a day's bird-watching. Green pressure groups start leaning on government, and governments pass laws to constrain companies from damaging the environment. In the West, a posse of pressure groups such as Greenpeace and the Environmental Defense Fund started up in the 1960s and helped bring about legislation in the 1970s and 1980s.
Growth also has indirect benefits for biodiversity. People clean up their environment in ways that help other species — through building sewage-treatment plants, for instance, and banning factories from pouring effluent into rivers. Prosperity and peace tend to go together, and conflict hurts other creatures as well as man, as the wars in the Congo have shown.
Richer countries generally have better governments, and conservation cannot work without an effective state. Agricultural yields rise, allowing more food to be produced on less land, and population-growth rates fall: In East Asia fertility has dropped from 5.3 children per woman in the 1960s to 1.6 now.
One consequence is that, in rich countries, conditions for other species are improving, by and large, and endangered creatures are moving away from the edge of the cliff. America's bald eagle, for instance, was down to 412 breeding pairs in the 1960s. There are now 7,066. Whale populations are mostly recovering thanks to a moratorium on commercial whaling.