A new study highlights the growing threat climate change poses to animal life, identifying over 3,500 species as at risk. Published in BioScience, the research also reveals significant gaps in our current understanding of how climate stressors affect global wildlife.

“This is the beginning of an existential crisis for wild animals on Earth,” said William Ripple of Oregon State University (OSU), who headed the study, in a press release. “Historically, over-exploitation and habitat destruction have driven biodiversity loss, but we now anticipate climate change becoming a third major force,” he added.

Ripple, a leading ecologist in OSU’s College of Forestry, worked with teams from both the US and Mexico. They analysed data from 70,814 species across 35 animal classes, using information from public biodiversity databases and assessments from the International Union for Conservation of Nature (IUCN).

Their findings show that in at least six major animal classes – including centipedes, spiders, corals and jellyfish relatives – 25% or more of species face threats linked to a changing climate. Other groups, though impacted to a lesser extent, are far from risk, the scientists stress.

Ripple expressed particular alarm for marine invertebrates, whose limited mobility makes it difficult to escape shifting environmental conditions. “We are particularly concerned about invertebrate animals in the ocean, which absorbs most of the heat from climate change,” he said.

Extreme weather events are already driving large-scale animal die-offs. According to Ripple, “The cascading effects of more and more mass mortality events will likely affect carbon cycle feedbacks and nutrient cycling,” which in turn may disrupt predator-prey dynamics, pollination and other vital ecological relationships.

Examples of such mortality events include a 90% decline in molluscs along Israel’s coast, the 2021 heatwave that killed billions of coastal invertebrates in the US Pacific Northwest, and massive coral loss – 29% of the Great Barrier Reef – in 2016. Not only invertebrates are affected: an estimated 4mn common murres – a seabird – perished in 2015-2016, and Pacific cod populations dropped by over 70% during the same marine heatwave. Additionally, roughly 7,000 humpback whales have died in the North Pacific, likely due to similar conditions.

A troubling discovery is that most animal groups have not yet been evaluated for climate vulnerability – only 5.5% of known species have IUCN assessments. “Our analysis is meant to be a preliminary effort toward assessing climate risk to wildlife species,” Ripple said. He called for a global tracking system for climate-related mass die-offs and faster assessments for unexamined species.

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