Nearly half of endangered mammals and a quarter of birds are already harmed by climate change -- a much bigger segment than previously thought, researchers have found.
Endangered primates and elephants are among the groups squeezed hardest by global warming, partly because they reproduce slowly and thus take longer to adapt to rapid environmental changes, they reported.
While most studies seek to predict global warming's future impact on animal survival, the new analysis found that for "large numbers" of threatened species, the damage was already being done.
The data suggests that "the impact of climate change on mammals and birds in the recent past is currently greatly under-appreciated," said a study in the journal Nature Climate Change this week.
According to co-author James Watson of the Wildlife Conservation Society, "something significant needs to happen now to stop species going extinct."
"Climate change is not a future threat anymore," he added.
Researchers had amassed data from 136 previous studies looking at 120 mammal and 569 bird species.
They compared documented changes in climate with growth or decline in population sizes, geographic ranges, body mass, and reproductive and survival rates.
The team then extrapolated the data to all land mammals and birds listed as threatened by the International Union for Conservation of Nature (IUCN).
Of the 873 listed mammal species, 414 (47 percent) have likely "responded negatively" to climate change, and 298 (just over 23 percent) of 1,272 birds, the researchers found.
Climate change can affect animals by limiting food and water, spreading disease and shrinking living space.
- Elephants, apes, marsupials affected -
Only seven percent of mammals and four percent of birds identified by the study were recognised by the IUCN as threatened by "climate change and severe weather", the authors said.
"We recommend that research and conservation efforts give greater attention to the 'here and now' of climate change impacts on life on Earth," they wrote.
"Conservation managers, planners and policy makers must take this into account in efforts to safeguard the future of biodiversity."
Along with elephants and apes, the team found that marsupials were among the worst affected mammals. Many had evolved, like primates, in stable tropical areas now becoming more volatile due to climate change.
Many of the hardest-hit bird species lived in aquatic environments, which are considered among the most vulnerable to temperature increase, the researchers added.
Meanwhile rodents that can burrow and avoid extreme weather conditions will be less vulnerable than other mammals to climate change, the team said.
In December 2015, 195 nations adopted the Paris Agreement to limit average global warming to "well below" two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels.
This would be achieved by curbing planet-heating greenhouse gases from burning coal, oil and gas.
But scientists warn that 2C is already too high, and that the world is on track for warming even beyond that, with disastrous consequences for life as we know it.