HOW THE BALD EAGLE SOARED AGAIN
Comment le nombre de pygargues à tête blanche s'est envolé à nouveau
Le pygargue à tête blanche, aussi appelé « aigle à tête blanche », emblème des États-Unis, semblait condamné à l’extinction dans les années 1960. Pourtant, grâce à une série de mesures de conservation menées sur le long terme, l’espèce n’est aujourd’hui plus menacée. Retour sur un beau succès écologique.
An avian stalker follows the course of a shallow river in Wisconsin. The river’s edge is wooded; fish occasionally leap from the water. With a beat of its dark wings, a bald eagle glides along, its head white in the early autumn sunshine. Tourists witnessing the majestic sight might believe they are seeing something rare. They are not. The bird, America’s national symbol, was driven almost to extinction in the 1960s, but its population is soaring again. In June 2007 federal officials said it no longer even counts as an endangered species. Its recovery is a dramatic environmental success. What made bald eagles great again?
A DRAMATIC FALL
2. The eagle’s fall was dramatic. By one estimate America had some 100,000 nesting pairs in 1782, when it was chosen as the national symbol because of its evident freedom and strength. (Benjamin Franklin lamented the choice, though, describing the eagle as a bird of “bad moral character. He does not get his living honestly.”) Within a century its numbers had plummeted.
3. The reasons were various. Settlers cleared the nesting habitats and waterways that were home to waterfowl and other prey. Farmers saw the birds as destructive scavenger-predators and hunted them. (They did have some grounds for complaint: a farmer of free-range chickens in Georgia, for example, blames bald eagles on his property for killing stock worth millions of dol-
lars over recent years.) And the birds were poisoned by accident, because they scavenged smaller birds that had already been filled with lead shot by hunters. By 1940 Congress noted that the eagles faced probable extinction, and passed an act that forbade people to do them any harm. By 1963 only 487 nesting pairs survived in mainland America, though Alaska had a healthier population.
LAWS
4. By a decade or so ago, however, nearly 10,000 nesting pairs were thought to be in the contiguous United States. The national total is probably substantially higher today, though in places like Vermont state rules still count the bird as threat- ened. The 1940 law no doubt helped with the recovery. Laws ordering a great expansion of protected natural areas, such as national and state parks, protected more habitat. Most important, however, was the banning of DDT. This chemical was used as a pesticide to control mosquitoes and other pests, especially in the early post-war years, and posed one of the gravest threats to the bald eagle’s survival. DDT that the eagles absorbed from contaminated fish weakened the shells of their eggs and limited reproduction (other birds, such as brown pelicans, were also affected). In 1972 the Environmental Protection Agency (EPA) banned the use of DDT, and the bird’s recovery since then has been strong. 5. Given threats to the actions of the EPA from the current American administration, that success is worth recalling. Nobody is seriously proposing a return to the widespread use of DDT in America, though occasional worries about mosquito-borne diseases, such as Zika or the West Nile virus, provoke questions on doing so. Getting the eagle back was a victory that Americans of any political persuasion could celebrate: it came about because officials employed a scientific approach to understanding an environmental threat, then implemented regulations to limit harm done by humans to nature.