The conservation group's Living Planet Report, published every two years, said humankind's demands were now 50 percent more than nature can bear, with trees being felled, groundwater pumped and carbon dioxide emitted faster than Earth can recover.
"This damage is not inevitable but a consequence of the way we choose to live," Ken Norris, Director of Science at the Zoological Society of London, said in a statement.
However, there was still hope if politicians and businesses took the right action to protect nature, the report said.
"It is essential that we seize the opportunity - while we still can - to develop sustainably and create a future where people can live and prosper in harmony with nature," said WWF International Director General Marco Lambertini.
Preserving nature was not just about protecting wild places but also about safeguarding the future of humanity, "indeed, our very survival," he said.
The report's finding on the populations of vertebrate wildlife found that the biggest declines were in tropical regions, especially Latin America. The WWF's so-called "Living Planet Index" is based on trends in 10,380 populations of 3,038 mammal, bird, reptile, amphibian and fish species.
The average 52 percent decline was much bigger than previously reported, partly because earlier studies had relied more on readily available information from North America and Europe, WWF said. The same report two years ago put the decline at 28 percent between 1970 and 2008.
The worst decline was among populations of freshwater species, which fell by 76 percent over the four decades to 2010, while marine and terrestrial numbers both fell by 39 percent.
To gauge the variations between different countries' environmental impact, the report measured how big an "ecological footprint" each one had and how much productive land and water area, or "biocapacity", each country accounted for.
Kuwaitis had the biggest ecological footprint, meaning they consume and waste more resources per head than any other nation, the report said, followed by Qatar and the United Arab Emirates.
"If all people on the planet had the footprint of the average resident of Qatar, we would need 4.8 planets. If we lived the lifestyle of a typical resident of the USA, we would need 3.9 planets," the report said.
Many poorer countries - including India, Indonesia and the Democratic Republic of Congo - had an ecological footprint that was well within the planet's ability to absorb their demands.
The report also measured how close the planet is to nine so-called "planetary boundaries", thresholds of "potentially catastrophic changes to life as we know it".
Three such thresholds have already been crossed - biodiversity, carbon dioxide levels and nitrogen pollution from fertilisers. Two more were in danger of being breached - ocean acidification and phosphorus levels in freshwater.
"Given the pace and scale of change, we can no longer exclude the possibility of reaching critical tipping points that could abruptly and irreversibly change living conditions on Earth," the report said.
Get Breaking news, live coverage, and Latest News from India and around the world on NDTV.com. Catch all the Live TV action on NDTV 24x7 and NDTV India. Like us on Facebook or follow us on Twitter and Instagram for latest news and live news updates.