shrubbery found in arctic
in the Alaskan Arctic have discovered that shrubs are growing larger and spreading across previously barren territory in the
tundra. The findings add to the scientific consensus that the region is gradually getting warmer.
Federal researchers combed through archives
of aerial photos, comparing new images to those of the same locations taken 50 years ago. Of the 66 aerial photos taken for
the study, growth increases were reported in 36 of those images, with the growth of some plants estimated to be as much as
In the remaining 30 images, no changes
to tundra shrub cover - either growth or reduction were found.
"The Alaskan Arctic for three decades has
gotten considerably warmer and experimental and model studies have shown that there should be more shrubs," said study co-author
Matthew Sturm, a geophysicist at US Army Cold Regions Research & Engineering Laboratory in Fort Wainwright, Alaska.
"We come along and find these photos, and
that's exactly what we're seeing," Sturm said.
The Army lab team said the study is the
first time that tundra growth has been analyzed in the high-latitude area through picture comparisons. The results appear
in the latest issue of the journal Nature.
The findings echo other Alaskan Arctic
studies performed with satellite imaging in the Alaskan Arctic, according to scientists who did not participate in the photo
"It certainly opens the door for more work
to support the suggestion that temperature is increasing," said Jeff Hicke, a research associate at the University of Colorado
at Boulder, who recently conducted a separate study on tundra vegetation growth using satellite imagery.
Aerial photos were taken in July of 1999
and 2000 from a low-flying aircraft over a swath of land measuring 248 miles from east-to-west and 93 miles north-south. The
tundra parcel is located between the Brooks Range and the Arctic coast.
They identify the exact area, including
the same shrub clusters, that the military originally photographed between 1948 and 1950.
Scientists said the new photographs clearly
illustrate a shift in the treeline over the past 50 years. They also show moose footprints, indicating the animals have migrated
northward to follow the shrubs.
"The treeline is definitely moving. You
can see the increase," said co-author Ken Tape, a research technician at the University of Alaska-Fairbanks Geophysical Institute.
"There's more spruce in this picture than in that picture. The treeline is moving north."
The deciduous shrubs below the treeline
were identified as dwarf birch, willow and green alder. The photos represented changes in height, diameter and density. The
largest increase in shrubbery was 15 percent, Tape said.
The research area is virtually uninhabited.
Because the tundra is frozen for as long as nine months during the intense Arctic winter and is spongy in the summer, the
region is not prone to fires.
"There's virtually no human impact, which
makes it a particularly good laboratory for studying these kinds of vegetative change," Tape said.
According to a study published in February
by the United Nations, climate change in polar regions is expected to be among the largest anywhere on Earth. Already, the
extent and thickness of Arctic sea ice have decreased, permafrost has thawed and the distribution and abundance of many species
has been effected.
A second U.N. climate summary released
in January estimated that global temperatures could rise as much as 10.5 degrees over the next century.
The Army lab study also suggests the additional
shrub growth will extract more carbon dioxide from a warming atmosphere, helping to moderate the effects of global warming