Farms, roads and towns are fast slicing up the world's wilderness, leaving 70 per cent of the world's remaining forested land less than one km from a forest edge, a US-led study showed.

The report, by two dozen researchers on five continents and using data the covers the past 35 years, said a rising human population was putting more pressure on forest animals and plants, which suffer greater risk of extinction as their habitats become fragmented.

Too close for comfort: the shrinking forestry buffer. Credit:Erin Jonasson

"We found the results surprising and frightening," Nick Haddad, a professor of biological sciences at North Carolina University who led the study, told Reuters. "The signs are all still downwards."

The Amazon and Congo basins were the main areas where vast tracts of forests remained far from human activity, according to maps published with the study in the journal Science Advances.