We've heard it so often it's become background noise: we're in the middle of a mass extinction event, the sixth one in Earth's history, and it's accelerating. Except new research suggests that story needs a significant revision.
Kristen Saban and John Wiens from the University of Arizona analyzed five centuries of extinction data across plants and animals—examining 912 documented extinctions and drawing on information from nearly 2 million species. What they found was counterintuitive: extinction rates peaked around a century ago and have actually been declining since, particularly over the last 100 years.
"We discovered that the causes of those recent extinctions were very different from the threats species are currently facing," Wiens said. The historical extinctions that dominate our extinction-crisis narrative were driven largely by invasive species on islands—rats, pigs, and goats introduced by humans that devastated isolated island populations like those in Hawaii. But today's primary threat is habitat destruction on continents, particularly in freshwater ecosystems. These are fundamentally different problems requiring different solutions.
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Start Your News DetoxThis matters because it exposes a flaw in how we've been thinking about extinction risk. Many modern predictions take historical extinction patterns and project them forward, assuming the same drivers will continue. But the researchers found that past extinctions are "weak and unreliable predictors" of current risk. Mollusks and vertebrates were hardest hit historically; today, mainland species facing habitat loss are most threatened. The patterns don't match.
Another surprise: extinction rates over the past 200 years show no acceleration linked to climate change. That doesn't mean climate change isn't a threat—Wiens was careful to clarify that point. It means the historical record doesn't yet show its full impact, and projecting from the past won't capture what's coming.
When the researchers looked at current threat assessments from the International Union for Conservation of Nature across 163,000 species, a clearer picture emerged. Today's threatened species are concentrated in different places, facing different pressures, than yesterday's extinct ones. The comparison suggests we've been using an outdated map to navigate a changed landscape.
None of this is permission to relax. Saban emphasized that biodiversity loss remains "a huge problem right now." But there's something quietly powerful in the finding that extinction rates have declined since the early 1900s. It suggests that conservation actually works. When we invest in protecting species, it shows up in the data.
The real takeaway isn't that extinction isn't happening or that we should stop worrying. It's that we need to talk about what's actually happening with precision, not catastrophic metaphor. "If we're saying that what is happening right now is like an asteroid hitting Earth, then the problem becomes insurmountable," Saban said. Understanding the real shape of the crisis—where it's concentrated, what's driving it, where we've already made progress—that's what opens the door to doing something about it.
