For those tuned into the environmental movement, mass extinction is more than just a scary-sounding phrase. Studies have shown that humans’ impact on the environment is swiftly eliminating entire species from the land and sea, and at a rate equivalent to major extinctions of the past. Geologic evidence has revealed five such mass extinctions – periods when the majority of the planet’s species have been eliminated – and current data shows the Earth is on the verge of a sixth one.

One of the last remaining amastrid land snail species on O‘ahu, Laminella. (Photo Credit: Kenneth A. Hayes / University of Hawai'i)

One of the last remaining amastrid land snail species on O‘ahu, Laminella. (Photo Credit: Kenneth A. Hayes / University of Hawai’i)

Yet, strange as it might seem, a recent study of Hawaiian snails reveals we may be even closer to that catastrophe than official sources claim.

To understand why, it’s important to first understand how we classify endangered animals. The International Union for Conservation of Nature (IUCN) is the preeminent authority on the matter, and its Red List officially states that 832 species have gone extinct since 1600. However, of the thousands of animals studied by the IUCN, invertebrates (i.e., spineless animals such as worms, insects and crustaceans) are severely underrepresented. This is skewing the data on endangered and extinct species because, though invertebrates make up less than one percent of the IUCN’s data, they comprise 95 to 99 percent of the planet’s biodversity.

What’s more, cataloging all the planet’s invertebrates under the IUCN’s strict guidelines would be extraordinarily difficult. Thus, to get a better idea of the planet’s rate of extinction, a group of scientists studied the Hawaii land snail family Amastridae.

The family comprises 325 species, 33 of which are classified by the IUCN as extinct. (Compared to other invertebrates, snails are much easier to track because they leave behind their shells.) In their assessment, published July 31 in the journal Conservation Biology, the scientists concluded that in fact 131 species of Amastridae are extinct. This dovetails with another recent study, authored by some of the same scientists, that estimates approximately 10 percent of 200 known land snail species have gone extinct worldwide. Compare that to the nine species that have been evaluated by IUCN and its assessment that three are extinct.

And while snails may not seem so significant to your daily life, the fact that this wide discrepancy exists between official and actual extinction numbers is a cause for major concern.

“The focus on birds and mammals and the proportionately negligible assessment of invertebrates masks a real crisis,” the researchers write.

In the Hawaiian land snails study, scientists used their data to estimate a much higher extinction figure than IUCN posits. Instead of 832 extinct species, they believe the number may be  closer to 130,000. In Hawaii, extinction rates may be as high as 14 percent per decade.

“We’re not criticizing IUCN, they’re not set up to estimate the number of species,” Robert Cowie, a University of Hawaii researcher who worked on both studies, told the Washington Post. “The point of the paper is to say, the vast, vast majority of invertebrates has not been assessed.”

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