A sweeping new analysis reveals that thousands of animal species, particularly invertebrates, face grave risks from climate change—while huge gaps in data leave many more species unaccounted for.
Key Points at a Glance
- More than 3,500 animal species identified as threatened by climate change
- Marine invertebrates are especially vulnerable due to their limited mobility
- Mass mortality events linked to climate extremes are on the rise
- Only 5.5% of described animal species have been assessed for climate risk
- Researchers call for urgent global integration of climate and biodiversity policies
In the unfolding drama of climate change, it’s not just polar bears and penguins that are in peril. A landmark study led by Oregon State University ecologist William Ripple has sounded a stark warning: more than 3,500 animal species across the planet face direct threats from climate change, while most of Earth’s known species remain unexamined for such risks.
Published in BioScience, the study leverages a massive dataset of 70,814 species spanning 35 animal classes. The researchers cross-referenced this biodiversity data with climate vulnerability assessments from the International Union for Conservation of Nature (IUCN). The result is both eye-opening and deeply concerning.
In six major animal classes—including marine invertebrates like anthozoans and hydrozoans, as well as arachnids and centipedes—at least one-quarter of the assessed species are already deemed threatened by climate change. These figures underscore what Ripple describes as an “existential crisis” for wild animals, as climate-related hazards become a new and formidable driver of biodiversity loss.
So far, overexploitation and habitat destruction have dominated the conversation around species decline. But climate change is rapidly emerging as an equally devastating force, triggering a wave of extreme events—marine heat waves, wildfires, droughts, and floods—that can wipe out entire populations in a single stroke.
One striking example: in 2021, billions of intertidal invertebrates died along the Pacific Northwest coastline during an unprecedented heat dome. In Israel, mollusk populations have collapsed by 90% due to rising ocean temperatures. And in 2016, nearly one-third of Australia’s Great Barrier Reef corals were lost following a severe marine heat wave.
But vertebrates are not spared. The same marine heat wave that devastated coral reefs also led to the starvation of 4 million common murres off North America’s Pacific coast. Meanwhile, Pacific cod saw a 71% population decline, and as many as 7,000 humpback whales are thought to have died from heat wave-related impacts.
Ripple warns that these cascading mass mortality events disrupt much more than individual species. They fracture food webs, destabilize ecosystems, and interfere with essential processes like nutrient cycling, pollination, and predation—threatening to unravel the fabric of life in entire biomes.
Even more troubling is what we don’t know. Of the 101 animal classes in the IUCN database, 66 have yet to have a single species evaluated for climate change vulnerability. The study’s 70,814 analyzed species represent only about 5.5% of all currently described animal species. Many invertebrates—especially those in oceans, which absorb the majority of the planet’s excess heat—remain in scientific obscurity.
The authors of the study are calling for urgent change. Ripple and his collaborators argue that a global database tracking climate-driven mass mortality events is essential. They also advocate for more frequent and inclusive climate risk assessments that consider a species’ ability to adapt to changing conditions.
There’s a critical need to move beyond the current vertebrate bias of the IUCN Red List. Despite making up less than 6% of named animal species, vertebrates receive the lion’s share of attention, leaving vast swaths of biodiversity in the dark.
Ripple emphasizes the importance of unifying biodiversity and climate strategies into a cohesive global policy. Without this integration, conservation efforts will fall short of addressing the true scale and complexity of the crisis. “Understanding the risk is crucial for making informed policy decisions,” he asserts.
Funded in part by environmental advocate Roger Worthington, the study was a collaboration between researchers in the U.S. and Mexico. It stands not just as a scientific achievement, but as a rallying cry to protect the vast, intricate, and still largely unexplored web of life now hanging in the balance.
Source: Oregon State University
