Species are vanishing at an unprecedented rate, but we're not yet at "mass extinction" levels

Extinction has always been part of life. Some events were enormous, like the asteroid strike that wiped out the dinosaurs. Others unfolded more quietly, reshaping ecosystems.

Today, people are driving species toward extinction at alarming rates through habitat destruction, invasive species, and climate change.

But does this mean Earth is in the midst of a new mass extinction? Not quite, according to a recent study led by John Wiens of the University of Arizona and Kristen Saban of Harvard University.

Their findings show that while many species have disappeared, entire genera are not vanishing at the same pace. The loss of higher taxonomic groups is rare, often localized, and has slowed in recent decades.

Why genus extinctions matter

Species matter, but a genus carries more weight. Each genus represents unique evolutionary history, sometimes stretching back millions of years. Losing one can erase distinct genetic, ecological, and functional traits.

The tuatara offers a stark example. It is the only living member of a reptile lineage that dates back more than 250 million years. If it vanished, an entire evolutionary branch would be gone forever.

Wiens and Saban reviewed more than 22,000 genera from the IUCN database. They wanted to know if higher-level losses were stacking up.

The researchers identified 102 extinct genera in the past 500 years, less than half a percent of those assessed.

Genus-level extinction is uncommon

The extinctions weren’t evenly spread. Birds have lost 37 genera and mammals 21 – together making up about 1.6% of their total.

Other groups fared far better: amphibians lost just one genus, reptiles three, and ray-finned fishes four. Arthropods lost 11 genera, plants 12, and mollusks 14 – though most mollusk losses were limited to isolated islands.

These findings highlight a bias. Mammals and birds, both studied closely, show higher genus-level losses. Insects, though far more numerous, are under-assessed.

Even so, the data suggest that genus-level extinction is still uncommon compared to species-level decline.

The island effect

Most genus-level extinctions happened on islands. About three out of four extinct genera were island endemics.

Isolated ecosystems magnify vulnerability. Invasive predators, hunting, and habitat change hit harder where species have nowhere else to go.

Examples are scattered across the globe. The Mascarene Islands lost multiple bird genera. The West Indies saw mammals disappear. Saint Helena’s mollusks were especially affected.

Even freshwater systems showed vulnerability. All four extinct genera of ray-finned fishes lived in rivers or lakes.

Slowdown in extinction rates

Extinction rates climbed between the 1500s and 1800s, hitting their peak in the late 1800s and early 1900s. The decades with the most losses were the 1890s, 1900s, and 1930s.

Since then, rates have slowed. That finding directly challenges earlier claims that extinctions are speeding up.

Why the slowdown? One reason may be conservation. Efforts to protect birds and mammals in the past century appear to have worked.

Another possible explanation for the slowdown is timing. Many of the most fragile lineages, especially on islands, disappeared over a century ago. What remains may be more resilient, at least against the threats of that time.

Counting extinctions is challenging

Counting extinctions isn’t simple. Insects, for example, are underrepresented in the IUCN database. They make up nearly half of all species, but few genera are assessed.

Even with that gap, genus-level extinction remains below half a percent for insects and other groups.

Another factor is classification. Birds and mammals often have fewer species per genus. This makes them more likely to lose entire genera when species vanish.

Reptiles and amphibians, which pack more species into each genus, appear less vulnerable in this way.

Possible but uncertain patterns

The study also tracked 37 genera listed as “possibly extinct.” Most of them were monotypic, consisting of only one species. Many were island or freshwater specialists, echoing the confirmed extinction patterns.

If all of the possible extinctions were confirmed, the total number would rise slightly. But even then, the trend of rarity and slowdown would hold.

The big picture is clear: the crisis is real, but it looks different when measured at higher levels of classification.

Why extinctions must be stopped

“A recent study suggested that extinctions of animal genera are rapidly accelerating and that these extinctions endanger human survival,” said Wiens.

“We found instead that extinctions of genera are very rare across plants and animals, that they were mostly of genera found only on islands, and that these extinctions actually slowed down over the last 100 years instead of rapidly accelerating.”

According to Wiens, there was never any evidence that these extinctions, which peaked ~100 years ago and occurred mostly on isolated islands, endanger human survival.

“We argue that the reason why future extinctions must be stopped is not because they threaten humans, but because it is morally wrong for humans to drive other species to extinction.”

Saban highlighted another important issue – how science is communicated. “Now more than ever, given the widespread mistrust in science, it is important that we conduct conservation research carefully and present it accurately,” she said.

Irreplaceable value of species

So, what does this mean? We are not in a mass extinction at the genus level. But that does not soften the blow of losing hundreds of species.

Threats are changing. In the past, invasive species and overhunting drove island losses. Now, climate change and habitat destruction loom large.

The study urges caution. Scientists should avoid exaggerating extinction trends but must still stress urgency. Every extinction matters, not just for ecosystems but as a moral responsibility.

Humanity has the choice to act, not because its survival depends on every genus, but because each species adds irreplaceable value to Earth’s living fabric.

The study is published in the journal PLOS Biology.

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