Just 3% of world’s ecosystems remain intact, study suggests
Pristine areas in the Amazon and Siberia may expand with animal reintroductions, scientists say
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.
Researchers suggest reintroducing a number of important species to 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 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.
“Much of what we consider as intact habitat is missing species that have been hunted by people, or lost because of invasive species or disease,” said Dr Andrew Plumptre, the lead author of the study, from the Key Biodiversity Areas Secretariat in Cambridge, UK. “It’s scary, because it shows how unique places like the Serengeti are, which have functioning and intact ecosystems.
“We’re in the UN decade of ecosystem restoration now, but it is focusing on degraded habitat,” he said. “Let’s also think about restoring species so that we can try and build up these areas where we’ve got ecologically intact ecosystems.”
The research, published in the journal Frontiers in Forests and Global Change, used maps of the ranges of 7,000 species in 1,500 and today from the International Union for Conservation of Nature’s Red List. Most data was for mammals, but it also included some birds, fish, plants, reptiles and amphibians. Many of the intact areas identified were in territories managed by indigenous communities.
“It might be possible to increase the ecological intact area back to up to 20% through the targeted reintroductions of species that have been lost in areas where human impact is still low, provided the threats to their survival can be addressed,” said Plumptre. He cited the successful reintroduction of wolves into Yellowstone national park in the US, which transformed the ecosystem.
Prof Pierre Ibisch, at the Eberswalde University for Sustainable Development in Germany, said finding just 3% of land was intact was “devastating”. He said: “We need to give nature significantly more space to carry us into the future, [but] I fear that the reintroduction of a few species in certain areas is not a gamechanger.” Ibisch said the analysis did not take account of the climate crisis. “Accelerating climate change is becoming the overarching threat to the functionality of entire ecosystems. Yesterday’s mammal intactness hardly tells us a lot about the functioning ecosystems in the [global heating] age.”