Meet Iowa’s 400,000 Year Old Living Fossil

Hello, Iowa Pleistocene snail.
Photo: USGS

Northeastern Iowa holds a 400,000 year old time capsule. Rather than vast, flat prairies, this region boasts a rolling landscape of bluffs and ravines spared by the earth-tamping force of the last Ice Age’s glaciers. And nestled in the leaf litter on rubble piles beside the region’s chilly bluffs lives a tightly-coiled, quarter-inch endangered snail.

Discus macclintocki, the Iowa Pleistocene snail, was once-common but is now a highly-specialized snail that lives in pockets of Illinois and Iowa, where underground ice keeps the ground above 14 degrees Fahrenheit in winter and below 50 degrees Fahrenheit in summer.

But an increase in human development to the region has threatened the snail’s existence. And climate change may well cause the snail to meet its final end as our overheating planet cuts into the snail’s habitat. Amid the extinction crisis, larger, charismatic animals receive much of the spotlight. But we’re losing plant and invertebrate species like Discus macclintocki the fastest, and they have their own stories to tell.

The snail inhabits The Driftless Area, a region where the Mississippi River flows between Minnesota, Wisconsin, Iowa, and Illinois. This rugged region holds little evidence of glacial till or sediment left across much of the surrounding region by receding glaciers from the Pleistocene era that spanned from 2,580,000 to 11,700 years ago. That lack of glacial till or “drift” is the source of the region’s name. Today, much of the area consists of plateaus carved by ancient erosion from snowmelt draining into the river, drainage patterns that don’t match the glaciated areas, and landforms like mesas, bluffs, and pinnacles exposing bedrock.

Algific talus slopes hide all sorts of wonders.
Photo: USFWS Midwest Region (Flickr)

Among the gorges are a specific kind of habitat called algific talus slopes, which are piles of rubble beside the bedrock cliffs they detached from. Ice in sinkholes beneath and near the slopes cool the air in the summertime and warm it in the wintertime, resulting in small patches of plants typical of more northern locations, like evergreen trees including Canada yew and balsam fir. In essence, a glacial-era habitat remains on these slopes. Threatened species like the small, blue, Northern Monkshood flowers and at least nine glacial relict snail species, including the Iowa Pleistocene snail.

Scientists thought that the species of snail that’s lineage stretches back 400,000 years was extinct until 1928 when they found it on these algific talus slopes, according to U.S. Fish and Wildlife Service. It was placed on the federal endangered species list in 1977. Today, it lives on at least 36 known sites across Iowa and Illinois, though research suggests there could be more. The International Union for Conservation of Nature does not list the species as endangered, citing that surveys have turned up more locations than previously thought, though they have not updated their assessment since 2004.

U.S. Fish and Wildlife Service protects the snail by restricting access to its breeding habitats—but they still consider it threatened by the potential for human development such as “logging, quarrying, road building, sinkhole filling and contamination, human foot traffic, livestock grazing and trampling, and misapplication of pesticides.”

Beyond these local threats, there’s also the overarching threat of climate change. Rising temperature imperil the snail’s incredibly specialized habitats by melting the ice that keep temperatures cool and air moist. Researchers at the University of Wisconsin ranked algific talus slopes as an ecosystem of “moderate to high” vulnerability to climate change, which in turn imperils the already endangered snail. Fish and Wildlife Service calls it a “major long-term cause of snail population decline.”  No wonder Iowans are so worried about the climate crisis.

The Iowa Pleistocene snail’s story is typical of many of the world’s most-threatened and recently-extinct species: unassuming invertebrates inhabiting a tiny and fragile habitat that humans could easily wipe off the map, intentional or accidentally. Curbing the extinction crisis requires caring about more than just the charismatic megafauna at zoos, but also these tiny denizens.

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