Pristine areas in the Amazon and Siberia may expand with animal reintroductions, scientists say

Deforestation in the Brazilian Amazon – one of the few fragments of wilderness undamaged by human activities. Photograph: Florian Plaucheur/AFP/Getty Images

Just 3% of the world’s land remains ecologically intact with healthy populations of all its original animals and undisturbed habitat, a study suggests.

These fragments of wilderness undamaged by human activities are mainly in parts of the Amazon and Congo tropical forests, east Siberian and northern Canadian forests and tundra, and the Sahara. Invasive alien species including cats, foxes, rabbits, goats and camels have had a major impact on native species in Australia, with the study finding no intact areas left.

The researchers suggest reintroducing a small number of important species to some damaged areas, such as elephants or wolves – a move that could restore up to 20% of the world’s land to ecological intactness.

Previous analyses have identified wilderness areas based largely on satellite images and estimated that 20-40% of the Earth’s surface is little affected by humans. However, the scientists behind the new study argue that forests, savannah and tundra can appear intact from above but that, on the ground, vital species are missing. Elephants, for example, spread seeds and create important clearings in forests, while wolves can control populations of deer and elk.

The new assessment combines maps of human damage to habitat with maps showing where animals have disappeared from their original ranges or are too few in number to maintain a healthy ecosystem. Some scientists said the new analysis underestimates the intact areas, because the ranges of animals centuries ago are poorly known and the new maps do not take account of the impacts of the climate crisis, which is changing the ranges of species.

It is widely accepted that the world is in a biodiversity crisis, with many wildlife populations – from lions to insects – plunging, mainly due to the destruction of habitat for farming and building. Some scientists think a sixth mass extinction of life on Earth is beginning, with serious consequences for the food, and clean water and air that humanity depends upon.