NASA’s Landsat program—which will see its newest satellite launched in 2021—has given us a view from space of forests, farms, fresh water resources, and cities across our planet since the early 1970s — the longest scientific
record of its kind. Now, researchers have used high-resolution Landsat data acquired since 1985 to show how the Arctic tundra has in many places been getting greener as the region’s overall temperatures rise — and 2020 saw a 10-15ºF “heat wave” which contributed to more wildfires and continued loss of sea ice.
From a NASA news release on Sept. 22, 2020:
“The Arctic tundra is one of the coldest biomes on Earth, and it’s also one of the most rapidly warming,” said Logan Berner, a global change ecologist with Northern Arizona University in Flagstaff, who led the recent research. “This Arctic greening we see is really a bellwether of global climatic change – it’s a biome-scale response to rising air temperatures.”
Berner and his colleagues used the Landsat data and additional calculations to estimate the peak greenness for a given year for each of 50,000 randomly selected sites across the tundra. Between 1985 and 2016, about 38% of the tundra sites across Alaska, Canada, and western Eurasia showed greening. Only 3% showed the opposite browning effect, which would mean fewer actively growing plants. To include eastern Eurasian sites, they compared data starting in 2000, when Landsat satellites began regularly collecting images of that region. With this global view, 22% of sites greened between 2000 and 2016, while 4% browned.
When the tundra vegetation changes, it impacts not only the wildlife that depend on certain plants, but also the people who live in the region and depend on local ecosystems for food. While active plants will absorb more carbon from the atmosphere, the warming temperatures could also be thawing permafrost, thereby releasing greenhouse gasses.
The research is part of NASA’s Arctic Boreal Vulnerability Experiment (ABoVE), which aims to better understand how ecosystems are responding in these warming environments and the broader social implications.
“We assessed pan-Arctic changes in tundra greenness using high spatial resolution Landsat satellite observations and found evidence to support the hypothesis that recent summer warming contributed to increasing plant productivity and biomass across substantial portions of the Arctic tundra biome during the past three decades… Overall, our high spatial resolution pan-Arctic assessment highlights tundra greening as a bellwether of global climatic change that has wide-ranging consequences for life in northern high-latitude ecosystems and beyond.”
— Berner, L.T., Massey, R., Jantz, P. et al. (Nature Communications)
The team did note that there were many areas of the Arctic that did not exhibit greening even though temperatures had been rising, which could be due to other factors such as drought, increasing wildfires, and changing hydrological activity like the thawing of permafrost.
Also, as this story was posted, the 2020 Arctic sea ice minimum was reported to have been the second-lowest on record while global CO2 levels in the atmosphere continue to rise — currently at 414 ppm (consistently measured from Mauna Loa in Hawaii at over 400 ppm since March 2015.) Learn more about how NASA is monitoring Earth’s warming climate here.