The earth’s wildlife population has been cut in half since 1970, according to the World Wildlife Fund’s 2014 Living Planet Report, released Tuesday.
The authors of the study blamed human intervention, including habitat loss, hunting, and fishing. The report also considered climate change a factor, but its influence was harder to quantify.
The study measured 10,000 populations of about 3,000 animal species to create an index of the world’s fish, birds, mammals, amphibians, and reptiles. Some populations have remained stable, but they were outweighed by the declines—especially among freshwater species.
Human activity is consuming the planet’s resources faster than they can regenerate, the study authors concluded. “For now, we can cut trees faster than they mature, harvest more fish than the oceans can replenish, or emit more carbon into the atmosphere than the forests and oceans can absorb,” says the report. “The sum of all human demands no longer fits within what nature can renew.”