A global analysis of Earth’s threatened and endangered species has upended our scientific understanding about the extent to which climate change is affecting wildlife.

“We are massively underreporting what is going on,” /wcs.academia.edu/JamesWatson"}}">James Watson, a co-author of the new study and director of science and research initiatives at the /www.wcs.org/"}}">Wildlife Conservation Society, told The Huffington Post.

The research, published Monday in the journal Nature Climate Change, estimates that 47 percent of mammals and 23 percent of birds on the International Union for Conservation of Nature’s Red List of Threatened Species have been negatively affected by our changing planet. Those estimates are shockingly higher than previous assessments, which the authors note had shown 7 percent of listed mammals and 4 percent of birds were affected.

The report adds to an ever-growing body of evidence that swift action is needed to tackle a phenomenon that’s driving a biodiversity crisis, sea-level rise, drought and extreme heat.

Julie Larsen Maher/Wildlife Conservation Society Elephants were among the most vulnerable to climate change effects, the study found.

For the analysis, a team of researchers from Australia, Italy and Britain combed through all relevant studies published from 1990 to 2015 that documented a species that was affected or not by changes in climate. For each of those more than 2,000 species, the authors categorized the effect as negative, positive, unchanged or mixed.

Of the 873 mammal species looked at, 414 were hurt by climate change, with elephants, primates and marsupials among the most vulnerable. For threatened birds, 298 of 1,272 species are experiencing negative effects, with waterfowl and birds who live at high altitudes being among the hardest hit, according to the findings.

Of course, effects vary greatly for each species. Overall, though, it’s clear that many more animals are in trouble than had been thought.

And given that the analysis looked only at mammals and birds, which are by far the most studied species but represent only a small percentage of the biodiversity on Earth, the problem could be far worse than the findings suggests, according to Watson.

“Most of these species haven’t even been assessed against climate change, so we’re clearly underreporting that,” he told HuffPost. “This is a bad story for birds and mammals, but it probably means that we are really, really getting it wrong for a lot of other species.”

The new study follows an analysis of threatened wildlife, which Watson also co-authored, showing that the biggest threat to biodiversity is not climate change, which gets a lot of attention, but age-old human activities, including logging, hunting and farming. Today, three-quarters of Earth’s land surface faces “measurable human pressures,” while just 3 percent of the world’s biodiversity hotspots remain unaltered, according to a global analysis Watson co-authored in August.

When it comes to assessing the effects of climate change on flora and fauna, Watson said, most studies look at what might happen to a population in the future, perhaps 50 or 100 years down the line. (A 2015 study, for example, found that if climate change continues unabated, 1 in 6 plant and animal species will become extinct.)

The problem with such forecasts, Watson argued, is they are “absolutely unhelpful for the here and now and what policymakers can do.”

“Climate change is already happening, and it’s going to get worse,” he said, adding it is essential for world leaders to reduce carbon emissions in an effort to keep global temperatures from reaching 2 degrees Celsius above what they were in pre-industrial times, as nearly 200 countries committed to do as part of last year’s historic Paris climate agreement.

“Nature is extremely resilient if you give it a chance,” Watson said. “But the big thing is acting now, not in 20 to 50 years time. Not making climate change a future threat, but prioritizing climate-smart actions now. Because every day, every minute, that we delay, you lose those opportunities.”