In just the last half-century, humans have caused a staggering, worldwide drop in the number of sharks and rays that swim the open oceans, scientists have found in the first global assessment of its kind, published in the journal Nature.
Oceanic sharks and rays have declined by 71 percent since 1970, mainly because of overfishing. The collapse is probably even more stark, the authors point out, because of incomplete data from some of the worst-hit regions and because fishing fleets were already expanding in the decades before they started their analysis.
“There is a very small window to save these iconic creatures,” said Nathan Pacoureau, a marine biologist at Simon Fraser University in Canada and the study’s lead author. More than three quarters of oceanic shark and ray species are now threatened with extinction, jeopardizing marine ecosystems and the food security of people in many nations.
The research offers the latest data point in what is a dismal trajectory for Earth’s biodiversity. From butterflies to elephants, wildlife populations have crashed in recent decades and as many as a million species of animals and plants are at risk of extinction.