Arctic summers are not what they used to be. The great wall of ice that as recently as the early 2000s extended far into the shallow Chukchi Sea north of the Bering Strait even in warmer months has retreated. The sea is so free of ice in summer that cargo and even cruise ships regularly ply its waters.
For the animals that live there, the rapid change may be devastating. Among them is the Pacific walrus, which relies on floating ice to rest between bouts of hunting for food on the seafloor. Without ice to rest on, more walruses are hauling out on land in unusually large numbers in summer, which can lead to stampedes where many animals—especially juveniles—are crushed to death.
Tracking this behavioral change is difficult. There’s been no consistent record-keeping of the timing and location of walrus haulouts in the Arctic. But in summer 2016, a group of researchers with the U.S. Geolological Survey compiled a database of all known haulouts since the 1800s, drawing on historic documents, oral reports and more recent scientific surveys. (You can read the full USGS report on the haulout data here.)
Mapping that data shows a species undergoing a shift.
Data sources:
U.S. Geological Survey
National Snow and Ice Data Center