When the Soviet Union launched Sputnik into orbit in 1957, the United States responded with its own spy satellites. The espionage program, known as Corona, sought to locate Soviet missile sites, but its Google Earth–like photography captured something unintended: snapshots of animals and their habitats frozen in time. Now, by comparing these images with modern data, scientists have found a way to track the decline of biodiversity in regions that lack historic records.
The researchers tested the approach on bobak marmot (Marmota bobak) populations in the grassland region of northern Kazakhstan. There, Soviets converted millions of hectares of natural habitat into cropland in the 1960s. The scientists searched the satellites’ black and white film images on a U.S. Geological Survey database for signs of the squirrellike animal’s burrows. They identified more than 5000 historic marmot homes and compared them with contemporary digital images of the region, mapping more than 12,000 marmot burrows in all.
About eight generations of marmots occupied the same burrows in the study area over more than 50 years, even when their habitats underwent major changes, the team reports today in the Proceedings of the Royal Society B. Overall, the researchers estimate the number of marmot burrows dropped by 14% since the ’60s. But the number of burrows in some of the oldest fields—those persistently disturbed by humans plowing grassland to plant wheat—plunged by much more—about 60%.
When their burrows were damaged by plowed fields, marmots would often return and rebuild. But the consistent human activity likely weakened marmot families, as the energy animals spent rebuilding took its toll on their health, the team says. The prolonged disturbance may have significantly reduced marmots’ population size in those areas over time, the authors say.
Researchers have long known that marmots use the same burrows over decades, says Daniel Blumstein, an ecologist and marmot expert at University of California, Los Angeles, who was not involved in the study. But the long-term decline of burrows in areas farmed years ago is surprising, he says.
The work may be the longest recorded modern response of a mammal to its habitat being developed for agriculture, says study author Catalina Munteanu, a geographer at Humboldt University of Berlin. The approach, she says, offers a “really exciting” chance to look at changes in species populations that are visible from space, such as termite mounds, beaver dams, grazing trails, and, in this case, burrows.
Blumstein agrees. Tools like this, he says, might help us reduce our impact on animal habitats by better managing our activities.