Only 3% of land on Earth still qualifies as ‘ecologically intact’, with undisturbed habitats and healthy populations of its native animal species, according to grim new research.
It is a much darker picture than that painted by previous assessments, which set this number much higher, estimating that 20% to 40% of the land is still intact. But these analyses, which focused specifically on habitat integrity, were mostly based on satellite images, which don’t provide much detail about what’s happening on the ground.
“The fieldwork done by many people clearly shows that there are species that have been lost in these areas of undisturbed habitat…large and medium carnivores and large and medium herbivores in particular,” wrote Andrew Plumptre, who heads the Key Biodiversity Areas Secretariat and was the study’s lead author, in an email. “Some have been lost or reduced in number to hunting by people, some have been lost to introduced invasive species, such as cats and dogs, and some to disease.”
IInstead of just looking at aerial images for the reportPublished Thursday in Frontiers in Forests and Global Change, Plumptre and his team also overlaid maps of human destruction of ecosystems with maps showing where animal species are too few in number to maintain a healthy ecosystem or have completely disappeared from their ranges. original distribution.
To assess integrity, the authors used three criteria. Like previous studies, they looked at habitat integrity, a measure of the influence humans have had on habitats. They also looked at the integrity of fauna, which is an indicator of how many of a land’s original species have gone extinct since antiquity (specifically since 1500 CE). And they assessed functional integrity, which determines where species are abundant and able to perform their ecological roles as top predators, seed dispersers or other functions. According to these last two measurements, terrestrial ecosystems are not doing very well.
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“Fauna integrity was 2.9% of the land surface and functional integrity was 2.8%,” Plumptre said. This means that approximately 97% of the land has been devastated by industry, hunting, the introduction of invasive species or other anthropogenic impacts.
The intact ecosystems the team has identified are in Congo, Tanzania, the Amazon rainforest, Siberia and southern Chile.
Even more troubling, the team discovered that only 11% of the ecologically intact land they identified is protected by the countries conservation laws. An even smaller part (only 4%) is covered by Key Biodiversity Areasor areas where the The International Union for Conservation of Nature says it is especially important to preserve wildlife.
All is not lost, however. The authors found that a critical element missing in large areas of otherwise untouched land is the disappearance of certain key species, particularly large mammals. Some of these large mammals have completely disappeared, but others still survive elsewhere. In these cases, the authors say that by reintroducing only a small number (between one and five) of species that play crucial functions in some areas could return up to 20% of the world’s land to ecological integrity.
The authors identify six important global locations where this method could be successful: eastern Russia, northern Canada, Alaska, the Amazon rainforest, the Sahara desert and the Congo rainforest. In these areas, although species populations have declined, there is still plenty of original foliage and habitat to support the animals if they are reintroduced.
The study argues that we need a new way of thinking about ecological health. At present, the authors say, restoration focuses primarily on restoring degraded habitats. It’s important, but it’s not enough.
“We should also be thinking about restoring species to regain ecological integrity over more of the Earth,” Plumptre said.
