Up to 48% of terrestrial ecosystems face “a high risk of extinction” if global warming levels rise between 3 and 5C, according to the worst-case scenario in a United Nations report published on Monday.
But there is hope to reverse that worst-case scenario, the report’s author said.
The Intergovernmental Panel on Climate Change (IPCC) report examines the possible long-term impact (from 2040 onwards) that climate change could have on humans and biodiversity by analyzing five different future scenarios.
The most optimistic projection, with an average temperature rise of just 1.5C (34.7F) above pre-industrial levels, predicts an extinction rate of between 3% to 14%.
Endemic species living in “biodiversity hotspots” — those that inhabit a single geographical area — face a particularly high risk.
The climate crisis could wipe out entire populations of native species living on small islands, 84% of those inhabiting mountainous regions, 54% living in oceans and 12% on continents, the IPCC report adds.
The report has detected changes, some of them irreversible, in the planet’s ecosystems due to extreme weather events directly linked to human activities.
Over half of the global species examined by experts have modified their habitat to cope with climate change, either by moving away from the Equator towards the Poles or by moving to higher altitudes.
“Other impacts are approaching irreversibility such as the impacts of hydrological changes resulting from the retreat of glaciers, or the changes in some mountain and Arctic ecosystems driven by permafrost thaw,” the report warns.
Extreme heat events have already triggered the first extinctions.
The white sub-species of the lemuroid ringtail possum, a small Australian mammal, disappeared after the 2005 Australian heatwave, and the Bramble Cays Melomys, a nocturnal rodent, was declared extinct in 2016.
“Climate change threatens to rapidly transform unique and threatened ecosystems, such as tropical rain forests, coral reefs, arctic and high-mountain ecosystems, as well as the Indigenous and forest-dwelling people whose livelihoods, cultures and identities are dependent on these ecosystems,” the report adds.
The assessment urges the international community to take measures to stem a loss in biodiversity and to push for the recovery of degraded ecosystems and increase the protection of nature reserves.
According to the report’s co-chair Hans-Otto Pörtner:
“By restoring degrading ecosystems and effectively and equitably conserving 30 to 50 percent of the Earth’s land, freshwater and ocean habitats, society can benefit from nature’s capacity to absorb and store carbon.”