Two summers ago, almost a decade after the
first infestation, the moths returned. “We got a few
berries, but not as many as we used to,” says
Chugach elder Ephim Moonin Sr., whose house in
the village of Nanwalek is flanked by tall salmon-
berry bushes. “Last year, again, there were hardly
For more than 35 years, satellites circling the
Arctic have detected a “greening” trend in Earth’s
northernmost landscapes. Scientists have attrib-
uted this verdant flush to more vigorous plant
growth and a longer growing season, propelled
by higher temperatures that come with climate
change. But recently, satellites have been picking
up a decline in tundra greenness in some parts of
the Arctic. Those areas appear to be “browning.”
Like the salmonberry harvesters on the Kenai
Peninsula, ecologists working on the ground have
witnessed browning up close at field sites across
the circumpolar Arctic, from Alaska to Greenland
to northern Norway and Sweden. Yet the bushes
bereft of berries and the tinder-dry heaths (
low-growing shrubland) haven’t always been picked up
by the satellites. The low-resolution sensors may
have averaged out the mix of dead and living vegetation and failed to detect the browning.
Scientists are left to wonder what is and isn’t
being detected, and they’re concerned about the
potential impact of not knowing the extent of the
browning. If it becomes widespread, Arctic browning could have far-reaching consequences for
people and wildlife, affecting habitat and atmospheric carbon uptake and boosting wildfire risk.
The Arctic is warming two to three times as fast as
the rest of the planet, with most of the temperature increase occurring in the winter. Alaska, for
example, has warmed 2 degrees Celsius since 1949,
and winters in some parts of the state, including
southcentral Alaska and the Arctic interior, are on
average 5 degrees C warmer.
An early effect of the warmer climate was a
greener Arctic. More than 20 years ago, researchers used data from the National Oceanic and
Atmospheric Administration’s weather satellites to assess a decade of northern plant growth
after a century of warming. The team compared
different wavelengths of light — red and near-infrared — reflecting off vegetation to calculate the
NDVI, the normalized difference vegetation index.
Higher NDVI values indicate a greener, more
productive landscape. In a single decade — from
1981, when the first satellite was launched, to
1991 — the northern high latitudes had become
about 8 percent greener, the researchers reported
in 1997 in Nature.
The Arctic ecosystem, once constrained by
cool conditions, was stretching beyond its limits.
In 1999 and 2000, researchers cataloged the
extent and types of vegetation change in parts of
northern Alaska using archival photographs taken
during oil exploration flyovers between 1948 and
1950. In new images of the same locations, such
as the Kugururok River in the Noatak National
Preserve, low-lying tundra plants that once grew
along the riverside terraces had been replaced by
stands of white spruce and green alder shrubs. At
some of the study’s 66 locations, shrub-dominated
vegetation had doubled its coverage from 10 to
20 percent. Not all areas showed a rise in shrub
abundance, but none showed any decrease.
Salmonberries are widely harvested during the summer
in southern Alaska’s coastal regions. The shrubs have
been hit hard by moth damage in recent years.
the green As the
Arctic warms up, it’s
getting greener, but some
pockets have been going
brown instead. Satellite
imagery and ecologists
on the ground have
observed browning in the
circled areas on this map.