Warming temperatures are driving Arctic greening

Date:
September 22, 2020
Source:
NASA/Goddard Space Flight Center
Summary:
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.



FULL STORY ==========================================================================
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.


==========================================================================
"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." The study, published this week in Nature Communications, is the first to measure vegetation changes spanning the
entire Arctic tundra, from Alaska and Canada to Siberia, using satellite
data from Landsat, a joint mission of NASA and the U.S. Geological Survey (USGS). Other studies have used the satellite data to look at smaller
regions, since Landsat data can be used to determine how much actively
growing vegetation is on the ground. Greening can represent plants
growing more, becoming denser, and/or shrubs encroaching on typical
tundra grasses and moss.

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.

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.

"Whether it's since 1985 or 2000, we see this greening of the Arctic
evident in the Landsat record," Berner said. "And we see this biome-scale greening at the same time and over the same period as we see really
rapid increases in summer air temperatures." The researchers compared
these greening patterns with other factors, and found that it's also
associated with higher soil temperatures and higher soil moisture. They confirmed these findings with plant growth measurements from field sites
around the Arctic.

"Landsat is key for these kinds of measurements because it gathers data
on a much finer scale than what was previously used," said Scott Goetz, a professor at Northern Arizona University who also worked on the study and
leads the ABoVE Science Team. This allows the researchers to investigate
what is driving the changes to the tundra. "There's a lot of microscale variability in the Arctic, so it's important to work at finer resolution
while also having a long data record," Goetz said. "That's why Landsat
is so valuable."

========================================================================== Story Source: Materials provided
by NASA/Goddard_Space_Flight_Center. Original written by Kate
Ramsayer. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Logan T. Berner, Richard Massey, Patrick Jantz, Bruce C. Forbes,
Marc
Macias-Fauria, Isla Myers-Smith, Timo Kumpula, Gilles Gauthier,
Laia Andreu-Hayles, Benjamin V. Gaglioti, Patrick Burns,
Pentti Zetterberg, Rosanne D'Arrigo, Scott J. Goetz. Summer
warming explains widespread but not uniform greening in the
Arctic tundra biome. Nature Communications, 2020; 11 (1) DOI:
10.1038/s41467-020-18479-5 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200922135742.htm

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