When U.S. spy satellites circled the globe at the height of the Cold War, trees were an afterthought for government agencies monitoring nuclear missile sites of the Soviet Union and its allies.
Half a century later, however, the more than 800,000 detailed black-and-white images created by these orbiting eyes are a trove of ecological data. Scientists have begun using the photos as a kind of time machine, providing insights into how ecosystems have changed since the mid-20th century.
New research mapping forests in Romania’s Carpathian Mountains – one of the wildest places remaining in Europe – illustrates the potential of these satellite images. There, scientists have created a detailed picture of which areas have been continuously forested since shortly after the end of World War II. The results highlight unprotected, high-value forests that are at risk of damage from logging and other activities. The implications stretch beyond the borders of Romania, offering a strategy that would work in poorly-mapped temperate forests that ring the globe.
“If we really want to understand the forest systems, we have to think about the history of those forests and this is an aspect that has been widely neglected so far because data was missing from that period,” said Catalina Munteanu, a biogeographer and postdoctoral researcher at the University of Freiburg in Germany, who led the research.
Old forests are an ecological treasure, storing vast amounts of carbon, harboring a plethora of species and preserving relationships between organisms that shape relatively intact ecosystems. While the value of such forests has been recognized for decades – whether it’s old-growth forests of northwestern North America or Amazonian jungles – not all of these forests have been identified, leaving them more vulnerable to destruction.
Munteanu witnessed this firsthand growing up in Brasov in the early 2000s. The Romanian city is surrounded by the Carpathian Mountains. She would hike through a seemingly pristine forest of beech and larch trees, then crest a hill and confront a clearcut.
Later, as a PhD student, Munteanu was looking for ways to help conserve forests in her home country and elsewhere. In conversations with an advisor at the University of Wisconsin in Madison, she wondered if images from the Central Intelligence Agency’s CORONA program of around 100 satellites– now declassified – might hold a key to better understanding the location of the most ecologically important forests and threats posed by development. “There’s a lot of news about the loss of old growth forest and valuable forest ecosystems in Romania, but we don’t know exactly where all the old growth forests are,” she said.
Backed with a European Union grant, Munteanu launched EcoSpy, a research project aimed at figuring out ways to use these images to better understand ecosystems around the world. While other scientists had already begun using these pictures, they were often confined to local and regional levels, partly thanks to the challenge of converting black-and-white photographs into useable digital information, said Munteanu.
For EcoSpy, a technical breakthrough came when a colleague found that software created to make sense of images from modern drones could process the older photographs. Working with researchers from Germany and Romania, she matched the CORONA images with newer ones from modern Landsat satellites to see which forests had remained untouched since at least the 1960s.
The scientists identified 7,380 square kilometers of older forests with high ecological value in the Carpathians, an area slightly larger than the state of Delaware, according to the study published in Conservation Biology. That’s nearly double the size of old-growth forests previously identified in the region.
The researchers also found that roughly half of these forests were at high risk of damage from people, based on how accessible forests were, the proximity of roads and towns, and local reliance on firewood.
These detailed maps could be a useful tool for conservations and forest managers, highlighting which valuable forest tracts are most endangered. “This is going to be able to pinpoint: If we care to conserve these forests, where do we start? Where are the best candidates?” said Munteanu.
The approach could be applied beyond Romania as well. The old spy images cover much of the globe. Munteanu thinks her team’s analysis of the satellite imagery could be used in similar temperate forests, which cover parts of Europe, North America and Asia.
Meanwhile, these old spy images are being used to decipher other ecological mysteries. In Romania, scientists are tracking the historic locations of ant hills to understand which environmental conditions determine where a certain species of ant lives. As part of EcoSpy, researchers found a drop in populations of ground-dwelling marmots in Kazakhstan as habitat was converted to farmland. Now, Munteanu is collaborating with people studying changes in forests in southern Germany and South America, as well as lakes on the Tibetan plateau.
While the Cold War might have eased, the demand for these byproducts is heating up.
Munteanu, et. al. “Using historical spy satellite photographs and recent remote sensing data to identify high-conservation-value forests.” Conservation Biology. Aug. 2021