The Climate Emergency is Killing Species

It's happening in my neighborhood. Probably yours, too.

By Richard Conniff

An adult saltmarsh sparrow in Rhode Island (Photo: Evan Lipton)

In a narrow and rapidly dwindling strand of salt marshes along the Atlantic Coast, from southern Maine into Virginia, a clever but risky breeding strategy has allowed one bird species to thrive for hundreds of thousands of years.

The female saltmarsh sparrow weaves her small, cup-like nest from grass. But she doesn’t locate it sensibly—or at least not in a way we would consider sensible—in the relatively high-and-dry areas of the marsh. She would have to compete with too many other bird species there, and face greater pressure from predators hungry for her nestlings. Instead, she’s “created this nice little niche,” says Mark Urban, an ecologist at the University of Connecticut, and builds her nest “right on the edge” along the high-tide line.

You can see where this is going. Over the past 15 years, the saltmarsh sparrow has lost an estimated 70 percent of its population. There’s now a high likelihood that it will become extinct within the lifetimes of today’s high school and college students.

The list of culprits includes a grass—an invasive phragmites—which now grows in a dense, 10-foot-high wall right down to the waterline in many East Coast salt marshes. But the main culprit is sea level rise brought on by climate change. Even in the most sheltered backwaters, saltmarsh sparrow nests are simply drowning.

It’s a harbinger, says Urban, of what is likely to happen to tens of thousands of other species as climate change advances.

Urban describes himself as an aquatic ecologist who would “prefer to be out looking around, trying to catch frogs and salamanders and trying to understand their life histories.” But seeing how climate change was already affecting those life histories, he chose to spend the past two years developing one of the most detailed pictures yet of just how climate change is putting species at risk of extinction.

His study, published this week in the journal Science, projects that, even with global temperatures at current levels—a long-term average of 1.3 degrees Celsius above pre-industrial levels—1.6 percent of all species are likely to become extinct.

That overall number—1.6 percent of all species—might not sound so bad at first glance. But based on the current scientific estimate that there are 10 million species on Earth, that means 160,000 species face a high risk of extinction because of climate change that’s already happened.

That is, they are at high risk even before global warming hits 1.5 degree Celsius. That’s the threshold to avoid the worst effects of global warming—with a 2.0 degree rise as the much riskier backstop—agreed to by 195 nations in signing the 2015 Paris Agreement on climate change.

Beyond the 1.5 level, Urban writes, “extinctions will accelerate rapidly.” He notes without further comment that current international commitments aimed at reducing greenhouse gas emissions would actually “elevate global temperatures to 2.7°C” and put five percent of all species at risk of extinction. That’s 500,000 extinctions, taking down one in every 20 species on Earth, or in our own backyards.

In the worst-case scenario warming could hit 5.4 degrees Celsius and put 29.7 percent species at risk. That’s almost three million extinctions—one in every three species. It may sound unlikely that we would ever allow climate change to advance to that catastrophic level. But a 2021 study in the journal Nature Climate Change calculated that greenhouse gas emissions already in the atmosphere will lead to a global temperature rise as high as 2.3 degrees Celsius—close to the level that would put five percent of species at risk of extinction.

The new study is a meta-analysis. That is, Urban analyzed data from 485 studies produced by 1485 scientists over the past thirty years, published in peer-reviewed journals, and covering most known species. The studies included new data from Africa, Asia, and other areas that have been neglected in the past. Urban’s goal was to weigh past projections and make a more accurate overall projection for climate change risk, and also break it down by geographic regions and categories of species at greatest risk.

Australia and New Zealand face heavy potential losses, Urban writes, because “many terrestrial species can only track climate change so far before encountering the sea.” South America also faces greater risk because of “projected losses from hyperdiverse biodiversity hotspots inhabited by species with small ranges and specialized niches.” Finally, species everywhere living in mountain, island, and freshwater excosystems will face increasing pressure from climate change. Amphibians rank at the top of the list of likely victims because of their sensativity to weather, limited ability to disperse, and other factors.

Climate change extinctions are of course already occurring. The best-known case is the Bramble Cay melomys, which vanished sometime after 2009 from a low-lying island off northern Australia, after sea level rise and extreme weather caused repeated inundation of its habitat.

But drowning isn’t the only way climate change kills. Mountain species everywhere have had to move steadily uphill to find the cooler temperatures that suit them. Researchers call this “the elevator to extinction,” because mountains sooner or later top out. On the Hawaiian island of Kaua'i, warming has also enabled invasive mosquitoes and introduced malaria to reach higher up the mountain slopes, pushing some birds farther uphill and apparently causing recent declines in two mountain bird species. Extreme drought and wildfires also kill.

In other cases, the role of climate change is more ambiguous. For instance, climate change didn’t start the chytrid fungus epidemic, which has driven more than 500 amphibian species to the brink of extinction, and pushed another 90, mostly tropical frogs, over the edge. But it may help it spread faster, because frog immune systems respond less effectively in unpredictable weather.

How many of those 500 afflicted amphibians will follow the first 90 to extinction? And what percentage of those extinctions are attributable to climate change? These are the kinds of questions Urban has tried to wrangle with in his new study. When I suggested that this sounded like dark, depressing mathematics, he demurred.

“It's bleak in terms of what could happen if we don't do anything,” said Urban. “But it does suggest that if we can manage to mitigate greenhouse gas emissions and keep the world from warming beyond 1.5 degrees Celsius, then we're on a path to … still, some extinctions. But we could protect and save many of those species if we set our mind to it. So it's really a call to action more than anything.”

That makes sense to me. We are in the thick of a global climate emergency, despite what the billionaires who are about to lead the U.S. government would like us to think. It’s out job to shake ourselves out of our despair by working to save those saltmarsh sparrows from being drowned all along the U.S. East Coast, to stop greater sage-grouse from being displaced by oil rigs in the West, to support any of those endangered 160,000 species—or is it 500,000?—we could be working to protect.

A saltmarsh sparow nest in Maine (Photo: Bri Benvenuti/USFWS)

If species extinctions don’t count as an emergency for you, then think of Laihaina, the former capital of the Kingdom of Hawaii, reduced to ash last year by wildfire. Think of the extreme monsoon that triggered mudslides this past July and killed hundreds of people in Kerala, India. Think of city streets almost anywhere suddenly turned into rivers, sweeping cars downstream with their owners trapped inside.

We can—must—also be working to face up to the cause of the problem—the seemingly endless greenhouse gas emissions from our own fossil fuel addiction. Maybe it seems like we can succeed in that work now only at the city and state level. But members of Congress are seeing their constituents being bankrupted, displaced, and killed by extreme weather. Don’t let them look the other way.

It’s tempting in the face of the magnitude of the climate emergency, to just go to sleep and let the Republicans get on with their mindless, profit-hungry “drill, baby, drill” agenda. But if we do that, if we ignore the way that phrase rhymes with “kill, baby, kill., we may soon end up among the dead.

Other Useful Reading

Beware that climate change documents on U.S. government websites are likely to vanish without explanation after January 20, 2025:

The meaning of the 1.5 degrees C climate threshold [U.S. government]

Trump energy pick misinterprets studies to support claims, scientists say [Paywall]

Climate Action Tracker [to see how different countries are living up to their Paris Agreements—or more often not.]