The population of wild animals, including fish, birds, mammals, and amphibians and reptiles have plummeted by 58% between 1970 and 2012, according to the latest Living Planet Report published by conservation group WWF on Wednesday.

If current trends continue the world could lose more than two-thirds of wildlife by 2020, The Times reported.

Worst affected are species that live in lakes, rivers and wetlands — these freshwater dwellers have seen an 81% drop in populations over the past four decades, according to WWF.

The rapid rate of decline is attributed to rising human populations, habitat loss and degradation, hunting and climate change.