États-Unis

Wildlife returns to one of US' most famous rivers

The splash was so loud that Lewis Pugh thought someone had jumped off the bridge he was swimming under. But then Pugh, in the midst of a month-long swim down the United States’ Hudson River, saw what had joined him in the water: a bald eagle. "This majestic creature spread its wings and lifted up right in front of us. I will never forget the sight of it," says the environmental advocate. The British-South African, who is a United Nations Patron of the Ocean, is in the tail end of a 517km swim down the Hudson. The journey is designed to cast a spotlight on the river’s resurgence – and the need to protect the world’s waterways from pollution, climate change and a range of other threats. The appearance of a bald eagle on the Hudson would have seemed nearly impossible a few decades ago. America’s national bird, they were on the verge of extinction in the northeastern United States, decimated by the widespread use of the pesticide DDT. But since a ban on the pesticide in 1972, the bald eagles have returned. During his swim, Pugh also saw a black bear, beavers, snakes and some snapping turtles, which can reach 30kg.

The return of wildlife to the Hudson, once one of the country’s most-polluted rivers, is seen in many quarters as a conservation success story. It comes after a decades-long effort to clean up the waterway and, for many, it is a promising sign for the future. In 1972 the United States passed the Clean Water Act, which stopped companies from routinely dumping toxins into the river. Bans on commercial fishing were introduced in 1976 and extended in 1985. In 2002, officials began dredging silt laden with polychlorinated biphenyls, better known as PCBs, which had contaminated a 320km stretch of the river. New York State passed a law that established the Hudson River Park Trust to operate and maintain a new public park and estuarine sanctuary along the Manhattan shoreline, one of many efforts to rewild the Hudson’s banks. Challenges remain, though. Old dams in some tributaries are still preventing fish from reaching their spawning grounds. As well, riverine planning is uncoordinated, as over 80% of the watershed is privately owned. Climate change is another challenge. Warmer ocean temperatures, causing sea-level rise, as well as more intense heatwaves, flooding and droughts, are affecting the river’s ecology. In an assessment in 2011, 70 of 119 wildlife species in New York state were found to be vulnerable to climate change, with mollusks and amphibians near the top of the list.

Freshwater ecosystems are particularly biodiverse, supporting about 10 per cent of all described species. Some 55 per cent of fish species depend on freshwater for their survival. These species are going extinct more rapidly than terrestrial or marine species, with around one-third of all freshwater biodiversity facing extinction due to invasive species, pollution, habitat loss and over-harvesting. In 2018 the World Wildlife Fund estimated that populations of animals living in fresh water experienced a far more drastic decline than elsewhere on the planet – 83% between 1970 and 2014.

Photo Endurance swimmer Lewis Pugh in his 517km journey down the Hudson River
UNEP