The math of extinction: how many species vanish every year?

History · Published 18 October 2026 Swipe more like this →

In short: To understand if humans are accelerating the loss of life, scientists first have to calculate the 'normal' pace of extinction. By looking at the fossil record, they can establish a baseline for how many species vanish naturally without human interference.

Determining the background extinction rate requires isolating natural processes from modern human activity. Studies of marine fossils suggest that species typically last between 1 and 10 million years. If we assume these extinctions happen independently and gradually—rather than through catastrophic events like the end of the Cretaceous Period 66 million years ago—we can derive a baseline. Based on these figures, if there were 1 million species on Earth, one would expect to see about 0.1 to 1 extinction per year.

There are several ways to quantify this 'normal' rate. One method is the 'million species years' (MSY) metric, which suggests approximately one extinction occurs per million species years. This means that if the planet hosted only one species, it would take one million years to go extinct. Another perspective is the specific rate for certain groups; for example, one bird species is estimated to go extinct every 400 years under background conditions. These figures serve as a critical yardstick for measuring the impact of modern drivers like habitat loss, pollution, and invasive species.

The contrast between these rates and recent history is stark. Over a period of 2,000 years, Polynesian migrants in the Pacific might have wiped out 2,000 bird species, which represents about 17 percent of the global total. In the Hawaiian Islands alone, humans and introduced animals like pigs, rats, and goats caused the loss of dozens of bird and plant species. While island ecosystems are notably sensitive, these examples demonstrate that human-induced extinction can occur at a velocity that dwarfs the geological baseline.

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