Cold war spy satellite images reveal long-term decline in biodiversity

Images taken by cold war spy satellites have revealed a long-term decline in biodiversity due to the expansion of farming in Kazakhstan over the past 50 years.

Catalina Munteanu at Humboldt University of Berlin, Germany and her colleagues analysed satellite images of Kazakhstan taken between 1968 and 1969 by US satellites spying on the Soviet Union and declassified in 1996. Instead of looking for nuclear weapons, as the US government was doing at the time, the researchers searched the images for marmot burrows.

By comparing the cold war images with satellite pictures taken between 1999 and 2017, Munteanu and her team discovered that the number of marmot burrows within the same 60,000 square kilometre area in northern Kazakhstan had fallen by 14 per cent between 1968 and 2017.

A significant amount of the decline appears to be due to the expansion of farming, which began in Kazakhstan after the end of the second world war, says Munteanu. An estimated 60 per cent of the burrows were lost in areas that were transformed into farmland.

These historical images are also helping to shed light on animal behaviour. “I was really surprised to find that the marmots were using the exact same burrows for half a century long,” says Munteanu. Given that this particular marmot species only live around 6 years on average, that means the same burrows were used over many generations.

Spy satellite data could be used to study historical biodiversity more broadly, such as by looking at the prevalence of beaver dams, termite mounds or colonies of large birds like flamingos or pelicans, says Munteanu. These declassified images go back further than other satellites, because they were among the first in orbit. “It’s a little goldmine of data,” she says.

“I never thought of using this as a source of data,” says Dan Blumstein at the University of California Los Angeles. Blumstein says this data provides a benchmark for understanding the effect of human development on current patterns of biodiversity.

Monitoring marmots in particular may prove important because they form a key part of the ecosystem, says Erle Ellis at the University of Maryland, Baltimore County. “Declines in their populations could be a useful indicator of a variety of ecological dangers, from extinctions to ecosystem collapse,” he says.