Climate change drives animal extinction worldwide: study

The Earth is about 1.3 degrees Celsius warmer today than it was in the late 1800s. This seemingly small increase has quite profound effects on the natural world. The bird has become smaller. The lizards, insects, and snails have changed colors. Some goats have become nocturnal. These are adaptations that help animals survive climate change.

However, many species have not adapted quickly enough. Rising temperatures are not only eroding animal populations, but also driving entire species to extinction, sparking wildfires that kill wildlife in Australia and the Amazon. A few years ago, an Australian rodent called Bramble Cay’s Melomys went extinct, largely due to rising sea levels. Rising temperatures spread diseased mosquitoes across Hawaii’s highlands, killing entire populations of certain bird species.

That’s the situation today. It’s already pitch dark. So what will happen to wild animal populations if, or rather when, the Earth gets even hotter?

This pressing question is at the heart of a new study published in the journal Science. This study analyzes how different degrees of warming compared to pre-industrial averages will affect the proportion of the world’s species at risk of extinction.

The numbers reported in the study are alarming, but they also highlight an important message. If countries could curb greenhouse gas emissions, they could save thousands of species from permanent extinction.

500,000 species at risk of extinction due to current climate policies

This new study is a meta-analysis, meaning it combines the results of other existing studies (485 of them, to be exact). It estimates the proportion of known plant and animal species around the world that are predicted to become extinct under different future climate scenarios. These scenarios include current levels of warming and targets under the Paris Agreement, the United Nations’ global agreement to limit climate change, as well as more extreme emissions scenarios.

Scientists still don’t know exactly how many species exist on Earth, so converting these percentages into the actual number of extinct animals is difficult. Ecologist Mark Urban, the study’s sole author, said scientists now believe there are more than 10 million species. The current estimated loss of species due to global warming is approximately 160,000 species, and would rise to 500,000 species if the world fails to enact additional policies to reduce carbon dioxide emissions. That’s a lot. We’re talking about the potential for 500,000 species to become extinct due to climate change.

“Every time temperatures rise, the risk of extinction is accelerating,” Urban, director of the Center for Biological Risks at the University of Connecticut, told Box.

To be clear, Urban is reporting a risk of extinction. This is different from certainty of extinction. He likened endangered species to a cracked water jug: “You can see the water coming out.” “But what we don’t know is how big the crack is, so we don’t know how long it will take until the water runs out, which means the species will go extinct.

This study also has some important limitations. A model like this is only as good as the data fed into it, said Crystal Mantica Pringle, a researcher at the Canadian Wildlife Conservation Society who was not involved in the study. And research tends to skew towards certain types of animals or areas that are easier (and cheaper) to study, such as the forests of the United States or Europe rather than the Arctic. But Mantika Pringle and Elijah McLean, a conservation ecologist at the University of Exeter who were also not involved in the study, say the study is sound. “This is a pulse check on where we are,” Mantica Pringle told Vox.

Frogs and animals in mountains and islands are most at risk

The paper also looked at which animals and habitats are most and least at risk from global warming. Birds, for example, are at low risk of extinction because they are easily mobile, Urban found. As the ideal habitat for birds moves to the polar regions and up the mountains, birds try to move with it. However, warming temperatures remain a serious problem for many bird species, and other studies suggest that birds face a high risk of extinction in North America.

Conversely, organisms that can’t move easily, such as plants and other water-dependent organisms, will be more at risk, Urban said. In fact, Urban’s analysis found that amphibians, including frogs, are the most sensitive to a warming climate. Climate change could intensify droughts, and frogs need water. Rising temperatures may also contribute to chytrid fungus, a deadly pathogen that has wiped out dozens of frog species. Additionally, amphibians typically do not migrate very far, making it difficult to simply move from one habitat to another.

In terms of different habitats, the analysis shows that mountains, islands, and freshwater ecosystems appear to be most vulnerable to climate change. Again, this is not surprising. Mountain-dwelling animals can move to higher elevations as temperatures rise, but eventually they reach the top only to literally run out of space. This has led some scientists to describe climate change as an “escalator to extinction” for mountain species.

Islands face similar space problems and tend to be home to species with low abundance to begin with. Additionally, they are already battling other threats, such as invasive species, which could be exacerbated by warming temperatures. This point is important. Climate change is just one threat, but it often intensifies other threats, such as droughts associated with deforestation and the spread of wildlife diseases.

Are these numbers really that bad?

Excluding the worst-case scenario for greenhouse gas emissions, the study predicts that a relatively small number of species will become extinct due to climate change, with rates in the single digits. Does it really matter?

That’s the widely accepted answer, at least among ecologists. Even a small percentage represents tens of thousands of species, each of which has value to human society, whether we realize it or not.

Sometimes a single animal species is extremely important to a community’s culture, such as the Chinook salmon, which is considered sacred by some Native American tribes in the American West. And we already know that nature has treatments for many life-threatening diseases. Researchers estimate that an astonishing 70% of antibiotics and cancer treatments in use today have their roots in natural organisms.

“Most humans love nature, and while it is an aspect of nature, biodiversity is also the foundation of our health, wealth and culture,” Urban said.

Allowing even one species to become extinct is like playing Russian roulette, he says.

“We don’t even know what we’re losing,” Urban said. “But once you actually lose a species, it’s really irreversible. That’s it.”