After the end of the Cold War, the United States declassified tens of thousands of images taken by two satellite systems, Corona and Gambit. They were used by scientists from the University of Virginia to follow the changes in the landscape and vegetation of the past half a century.
A number of high resolution photographs show the tundra of Eastern Siberia, where the US government was looking for rocket launchers and nuclear weapons storage. The authors of the study realized that the images can be useful for studying the vegetation of the tundra and its changes. Scientists compared photos of 11 different places taken in 1961-1980, and modern images from satellites. In addition to studying the images, scientists undertook several expeditions to Siberia to explore the same areas on the spot.
The authors of the work noticed that over a few decades, a high shrub and small trees spread strongly: alder, willow, birch and cedar stlanik. In some places, their area increased by 26%. “We know from satellite data that the Arctic is” greening “the last 35 years or so. However, the Siberian tundra remained practically unexplored for a long time. We knew that the same processes were going on here. Vegetation grows taller, more diverse and occupies large areas, “said one of the authors of the work, Professor of the University of Virginia Howie Epstein.
According to the researchers, although these phenomena are most likely associated with global warming, in general, their causes are much more complicated. So, with the spread of vegetation, more solar energy is absorbed, and not reflected, as from snow, which additionally raises the temperature. The spread of vegetation also leads to changes in the composition of the fauna.
As the authors of the paper note, in recent years they began to notice the reverse process – the reduction of the area occupied by bushes and trees. “We do not yet know exactly why this is happening, but it is clear that the spread of vegetation in the tundra is a more complicated process than is commonly believed. We still have a lot of work to understand the reasons for the changes in the Arctic and their mutual influence with global warming, “Epstein noted.
