The average size of wildlife populations has plummeted more than two-thirds in less than 50 years because of deforestation and rampant overconsumption, experts have said in a stark warning to save nature in order to save ourselves, Al Jazeera reports.

Human activity has severely degraded three-quarters of all land and 40 percent of the Earth's oceans, an accelerating destruction of nature that will have untold consequences on health and livelihoods, the World Wildlife Fund (WWF) said in its annual Living Planet Report on Thursday, September 10.

The Living Planet Index, which tracks more than 4,000 species of vertebrates, warned that increasing deforestation and agricultural expansion were the key drivers behind a 68-percent average decline in populations between 1970 and 2016.

The report, a collaboration between WWF International and the Zoological Society of London, warned that continued natural habitat loss increased the risk of future pandemics as humans expand ever closer into contact with wild animals.

The report, with contributions from about 125 experts, said that of the more than 4,000 vertebrate species studied, those that live in freshwater suffered an 84-percent decline.