Most of Earth’s terrestrial habitats have lost their ecological integrity, including areas previously categorised as being intact, a study published in the journal Frontiers in Forests and Global Change shows.
The study analyzed three factors to assess the integrity and intactness of Earth’s ecosystems. The extent to which people have made changes to the land, the number of animal species lost from a habitat, and the number of individuals of a key species – a species needed in an functioning ecosystem – still present. Previous surveys often overlooked the last two factors.
“We know intact habitat is increasingly being lost, and the values of intact habitat have been demonstrated for both biodiversity and people,” lead study author Andrew Plumptre, biodiversity expert at the University of Cambridge’s Conservation Research Institute, said in a news release. “But this study found that 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.”
Previous efforts to quantify and map ecosystem integrity have focused exclusively on the influence of human activity — including the incursion of human settlements, roads and light and noise pollution — on ecosystems all over the world. Estimates suggest between 20 and 40 percent of terrestrial habitat is free from direct human influence. But humanity impacts much larger areas by air and water pollution, introduction of alien species, and by changing the climate.
Plumptre and his colleagues combined data on human impacts and loss of animal species from various global databases to map the ecological integrity of different regions. They compared current plant and animal diversity levels in intact habitat with historical biodiversity records.
“We only find about 2 to 3 per cent of the Earth’s land is where you could be considered as having the same fauna and flora that you had 500 years ago, in pre-industrial times, before major human impacts had occurred,” Plumptre concludes.
Areas identified as functionally intact included east Siberia and northern Canada for boreal and tundra biomes, parts of the Amazon and Congo basin tropical forests and the Sahara Desert. Of the 2 to 3 percent of ecologically intact sites, only 11 percent lie within environmentally protected areas. However, many other of the intact sites, including parts of the Sahara, Amazon and northern Canada, are within territories managed by indigenous communities, which have played a role in maintaining their ecological integrity.
The study also show that Earth’s terrestrial ecosystems could be restored, as the habitat is still intact, but key species are missing or the biodiversity is significantly reduced. Ecosystem fragmentation is another problem. Many small habitats are still intact, but as they lack connections, they can’t support as many species as one single habitat of the same size could.
“The results show that it might be possible to increase the area with ecological intactness back to up to 20 percent 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 and numbers rebuilt to a level where they fulfill their functional role.”
“Conservation of intact ecosystems is critical for the maintenance of biodiversity on Earth, and in turn for the services that these ecosystems provide to humans,” says co-author Kimberly Komatsu.
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