Science Adviser, 6 December 2024

Climate change alone could kill off more than a hundred thousand species

The Molokaʻi creeper, a flame-red songbird, is one of eight bird species in Hawaii that the U.S. Fish and Wildlife Service declared extinct last year. The cause? Rising temperatures allowed mosquitos to creep into its mountain habitat, infecting the birds with deadly malaria. Many more extinctions will come from climate change, according to an analysis published this week in Science, which estimates that 160,000 species are already in peril.

That climate change is a lethal threat is no surprise. Many researchers have predicted as much, often using computer models that correlate specific species’ habitat conditions with likely change from climate models. The new work pulls together 485 of these studies into a global estimate of how the threat increases as average temperatures continue to rise.

Like the Molokaʻi creeper, mountain-dwelling species are particularly at risk, the study confirms. These creatures have nowhere to migrate as temperatures climb. Also in dire straits are island ecosystems and rivers and lakes. More broadly, Australia and New Zealand are likely to experience higher rates of extinction from climate change, compared to other continents. That’s because species that migrate poleward in search of cooler habitat will eventually be driven into the sea.

With current warming now at 1.3°C above the pre-industrial average, an estimated 1.6% of species around the world are in danger of extinction from climate change. The reasons include heat stress, habitat change, invasive species, and other dangers. If temperature rises another 2.7°C—the amount likely given current pledges to reduce emissions—then 5% of species will be threatened with extinction from warming. Beyond that? Don’t even ask.

Science, 5 December 2024

Climate change extinctions

Climate change is expected to cause irreversible changes to biodiversity, but predicting those risks remains uncertain. I synthesized 485 studies and more than 5 million projections to produce a quantitative global assessment of climate change extinctions. With increased certainty, this meta-analysis suggests that extinctions will accelerate rapidly if global temperatures exceed 1.5°C. The highest-emission scenario would threaten approximately one-third of species, globally. Amphibians; species from mountain, island, and freshwater ecosystems; and species inhabiting South America, Australia, and New Zealand face the greatest threats. In line with predictions, climate change has contributed to an increasing proportion of observed global extinctions since 1970. Besides limiting greenhouse gases, pinpointing which species to protect first will be critical for preserving biodiversity until anthropogenic climate change is halted and reversed.