More than 3,500 animal species are directly threatened by climate change

Climate change is rapidly joining overexploitation and habitat destruction as a third major driver of global biodiversity loss.

A sweeping analysis has recently identified at least 3,500 animal species that are directly threatened by rising temperatures, intensifying storms, droughts, and other climate-related stresses.

The research, led by Oregon State University ecologist William Ripple, draws on international databases to show that risk is especially acute for invertebrates, particularly marine species that cannot easily move away from warmer waters.

The experts warn that true vulnerability is likely far greater because most animal groups have never been formally assessed for climate danger.

“We’re at the start of an existential crisis for the Earth’s wild animals,” Ripple said. “Up till now, the primary cause of biodiversity loss has been the twin threats of overexploitation and habitat alteration, but as climate change intensifies, we expect it to become a third major threat to the Earth’s animals.”

Animals are vulnerable to climate change

Ripple and colleagues analyzed records for 70,814 species across 35 taxonomic classes, relying on the International Union for Conservation of Nature’s threat categories.

The researchers discovered that in six whole classes – arachnids, centipedes, anthozoans, hydrozoans, and two other invertebrate groups – at least one-quarter of species are judged vulnerable to climate change.

Other classes, including mammals, birds and reptiles, contain smaller but still significant proportions of climate-imperiled members. The oceans stand out as a danger zone because seawater absorbs most excess heat from greenhouse forcing.

“We are particularly concerned about invertebrate animals in the ocean, which absorbs most of the heat from climate change,” Ripple explained. “Those animals are increasingly vulnerable because of their limited ability to move and promptly evade adverse conditions.”

Mass mortality events

In recent years extreme climate events have delivered dramatic proof of these vulnerabilities. Off Israel’s coast, a 90 percent crash in mollusk abundance followed a jump in sea-surface temperature.

During the 2021 Pacific Northwest heat dome, billions of intertidal mussels, clams, and snails died in a matter of days. A severe marine heatwave in 2016 bleached nearly 30 percent of Australia’s Great Barrier Reef.

Terrestrial and pelagic vertebrates have suffered too: an extreme warm spell in 2015-2016 altered the marine food web in the North Pacific, starving four million common murres, slashing Pacific cod numbers by 71 percent, and contributing to the loss of roughly 7,000 humpback whales.

Ripple noted that such mass mortality events reverberate through ecosystems. “The cascading effects of more and more mass mortality events will likely affect carbon-cycle feedbacks and nutrient cycling.”

“Those effects also likely will have an impact on species interactions such as predation, competition, pollination and parasitism, which are vital for ecosystem function.”

Missing data on a massive scale

Although the headline figures are sobering, the authors emphasize that they represent only a fraction of the problem.

Sixty-six of the planet’s 101 recognized animal classes have not had any species evaluated for climate risk by the IUCN, and the 70,814 species examined in the study account for just 5.5 percent of all described animals.

“Our analysis is meant to be a preliminary effort toward assessing climate risk to wildlife species,” Ripple said.

“Understanding the risk is crucial for making informed policy decisions. We need a global database on mass mortality events due to climate change for animal species in all ecosystems, and an acceleration in assessing currently ignored species.”

The Red List itself is heavily skewed toward vertebrates, which make up fewer than six percent of named animal species, leaving the vast majority of invertebrates – essential to pollination, soil health, and marine food webs – largely unexamined.

Climate and biodiversity policies

Ripple argued that improved risk assessments must be coupled with policies that synchronize biodiversity conservation and climate mitigation.

“There is also a need for more frequent climate risk assessments of all species and better consideration of adaptive capacity,” he added. “We need the integration of biodiversity and climate change policy planning on a global scale.”

He and his co-authors call for real-time monitoring of die-off events, expansion of citizen-science initiatives to cover overlooked taxa, and incorporation of species’ dispersal abilities and genetic diversity into risk models.

Only with such detailed knowledge, they contend, can land managers and lawmakers craft interventions that give vulnerable species a fighting chance.

Urgency to protect animals

With global temperatures already flirting with the 1.5°C threshold that scientists warn will unleash accelerating hazards, the time for closing data gaps is rapidly shrinking.

The new study shows that climate change is no longer a distant or incremental danger for wildlife; it is a present crisis that compounds long-standing threats.

Whether governments heed the warning will decide how many species remain confined to the 3,500-strong endangered column – and how many more quietly slide into it as the planet continues to warm.

The study is published in the journal BioScience.

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