Habitat destruction in a rainforest in Ecuador.

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 kilometre 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.

“We found the results surprising and frightening,” Nick Haddad, a professor of biological sciences at North Carolina University who led the study, said. “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.

In Asia, New Guinea, Russia, Canada and the Nordic nations, human activity steadily encroached on other huge forests.

Overall, the scientists wrote that “70 per cent of remaining forest is within one kilometre of the forest’s edge” – equivalent to a few city blocks.

“The expansion of human populations will inevitably continue to reduce and fragment natural areas,” they wrote, unless there were gains in agricultural yields and efficiency.

Another scientific report in 2011 projected that the world’s cropland would have to expand by 18 per cent by 2050 from the current 1.53 billion hectares to feed a rising world population.

The expansion of human populations will inevitably continue to reduce and fragment natural areas

And other estimates indicate that urban areas will also have to expand sharply, to 0.18 billion hectares by 2030.

The study said animals and plants are under threat from fragmentation which puts forests in range of humans, changing micro-climates and new, rival species from outside the forests.

“Fragmented habitats reduce the diversity of plants and animals by 13 to 75 per cent, with the largest negative effects found in the smallest and most isolated fragments of habitat,” it said.

Deforestation is a threat to animals ranging from jaguars in Brazil to orangutans in Indonesia, as well as other creatures such as birds, butterflies and frogs in addition to many rare plants.

In 2010, governments agreed a goal of setting aside 17 per cent of the world’s land area in wildlife parks and other protected areas by 2020, up from 12.7 per cent in 2010.