Warming temperatures are driving Arctic greening

24.09.2020

As Arctic summers warm, Earth’s northern landscapes are changing. Using satellite images to track global tundra ecosystems over decades, a new study found the region has become greener, as warmer air and soil temperatures lead to increased plant growth.

–These types of studies, in which we pool detailed
datasets from respective partners spread throughout the world, help us to better
synthesise otherwise disparate findings to understand what is happening across the
entire circumpolar North. The big picture that greening is not consistent among
different regions raises questions we need to ask next regarding drivers and
feedbacks, says research professor Bruce Forbes from
Arctic Centre, University of Lapland.

His team has provided
detailed ground-level baseline data on annual growth of tundra shrubs in relation to
climate, i.e. dendroclimatology, at sites in West Siberia and northernmost
Fennoscandia.

–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 this biome-scale
response to rising air temperatures.

The study, published
this week in Nature Communications, is the first to
measure vegetation changes across the Arctic tundra, from Alaska and Canada to
Siberia, using satellite data from Landsat, a joint mission of NASA and the U.S.
Geological Survey. Landsat data can be used to determine how much actively growing
vegetation is on the ground – greening can represent plants growing more, becoming
denser, or shrubs encroaching on typical tundra grasses and moss.

When the tundra vegetation changes, it impacts not only the
wildlife that depend on the 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, releasing greenhouse gasses. The research is part NASA’s Arctic Boreal
Vulnerability Experiment (ABoVE), which aims to better understand how ecosystems are
responding in these warming environments and its broader implications.

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, since that’s
when Landsat satellites began collecting regular images of that region. With this
global view, 22% of sites greened between 2000 and 2016, while 4% browned.