Only 3% of the world’s ecosystems remain intact, study finds | Wildlife

According to a study, only 3% of the world’s land remains ecologically intact with healthy populations of all its native animals and undisturbed habitat.

These fragments of wilderness undamaged by human activities are mainly found in parts of the rainforests of the Amazon and Congo, the forests and tundra of eastern Siberia and northern Canada 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 undisturbed areas.

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 integrity.

Questions and answers

What are the five biggest threats to biodiversity?

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According to the United Nations Convention on Biological Diversity, there are five main threats to biodiversity. In descending order, these are: changes in land and sea use; direct exploitation of natural resources; climate change; pollution and invasive species.

1. For terrestrial and freshwater ecosystems, land-use change has had the greatest relative negative impact on nature since 1970. More than a third of the planet’s land mass and nearly 75% of freshwater resources are now devoted to plant or animal production. Along with the doubling of the urban area since 1992, features such as wetlands, scrubland and woodland – on which wildlife depends – are being leveled out of the landscape.

2. Direct exploitation of organisms and non-living matter, including logging, hunting and fishing, and soil and water extraction are all negatively affecting ecosystems. In marine environments, overfishing is considered the most serious driver of biodiversity loss. According to a 2005 Millennium Ecosystem Assessment, a quarter of the world’s commercial fisheries are overexploited.

3. The climate crisis is dismantling ecosystems at all levels. Extreme weather events such as tropical storms and floods destroy habitats. Warmer temperatures also change the timing of natural events, such as the availability of insects and when birds hatch their eggs in the spring. The distribution of species and their range are also changing.

4. Many types of pollution are increasing. In marine environments, pollution from agricultural runoff (mainly nitrogen and phosphorus) causes enormous damage to ecosystems. Agricultural runoff causes toxic algal blooms and even “dead zones” in the worst affected areas. Marine plastic pollution has increased tenfold since 1980, affecting at least 267 species.

5. Since the 17th century, invasive species have contributed to 40% of all known animal extinctions. Nearly a fifth of the Earth’s surface is threatened by plant and animal invasions. Invasive species alter the composition of ecosystems by displacing native species.

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Previous analyzes have identified wilderness areas based largely on satellite imagery and estimated that 20-40% of the Earth’s surface is minimally affected by humans. However, the scientists behind the new study say forests, savanna and tundra may appear untouched from above but, on the ground, vital species are missing. Elephants, for example, spread seeds and create large clearings in forests, while wolves can control deer and elk populations.

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

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The world is widely believed to be in a biodiversity crisis, with many wildlife populations – from lions to insects – plunging, mainly due to habitat destruction for agriculture and construction. Some scientists believe a sixth mass extinction of life on Earth is beginning, with serious consequences for the clean food, water and air that humanity depends on.

“Much of what we consider untouched habitat is made up of missing species that have been hunted [and poached] by people, or lost to invasive species or disease,” said study lead author Dr Andrew Plumptre, from the Key Biodiversity Areas Secretariat in Cambridge, UK. “It’s quite scary because it shows how unique places like the Serengeti are, which actually have functioning and fully intact ecosystems.

“We are now in the United Nations Decade for Ecosystem Restoration, but it focuses on degraded habitat,” he said. “Let’s also think about species restoration to try to build these areas where we have ecologically intact ecosystems.

The research, published in the journal Frontiers in Forests and Global Change, used range maps of 7,000 of 1,500 species currently on the International Union for Conservation of Nature’s Red List. Most of the 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. The analysis did not include Antarctica.

“It may be possible to increase the ecologically intact area by up to 20% through the targeted reintroduction of species that have been lost to areas where human impact is still low, provided that threats to their survival can be processed,” Plumptre said. He cited the successful reintroduction of wolves to Yellowstone National Park in the United States, which transformed the ecosystem.

Professor Pierre Ibisch, from the Eberswalde University for Sustainable Development in Germany and not part of the study, said finding that only 3% of the land was untouched was “predictably devastating”. He said: “We need to give nature a lot more room to carry us into the future, [but] I fear that the reintroduction of a few species in certain areas will change the situation. »

Ibisch said the analysis did not take into account the climate crisis. “Accelerating climate change is becoming the overriding threat to the functionality of entire ecosystems. The integrity of yesterday’s mammals tells us very little about the functioning of ecosystems in the [global heating] age.”

Professor James Watson from the University of Queensland, Australia, said: “This study underestimates many efforts by ecosystem scientists to map and save ecologically intact places across the planet. It uses maps for species that are essentially best guesses, meaning the message of where ecosystems are actually still roughly intact is clearly understated.

Plumptre acknowledged that species range maps were relatively crude and said the 3% figure was a “rough estimate”. He said: “The problem is that, at the moment, we don’t have any other cards.” Scientists should then focus on specific regions and use more detailed human impact and species data to identify ecologically intact sites, he said.

In January, more than 50 countries pledged to protect nearly a third of the planet by 2030 to halt the destruction of the natural world. “Make efforts to keep these [intact] places is very important,” said Plumptre. “They are so rare and special, and show what the world was like before humans had a major impact, helping us measure how much we have lost.”