12 October 2006
FOR IMMEDIATE RELEASE
12 October 2007
FAIRBANKS, Alaska -- A first-of-its kind analysis of fifty years of
remotely sensed imagery from the 1950s to 2002 shows a dramatic
reduction in the size and number of more than 10,000 ponds in Alaska.
The analysis, by University of Alaska Fairbanks scientists and
published this week in the Journal of Geophysical Research, indicates
that these landscape-level changes in arctic ponds are associated
with recent climate warming in Alaska and may have profound effects
on climate and wildlife.
Over the past 50 years, Alaska has experienced a warming climate with
longer growing seasons, increased permafrost thawing, an increase in
water loss due to evaporation from open water and transpiration from
vegetation, and yet no substantial change in precipitation.
The shrinking of these closed-basin ponds may be indicative of
widespread lowering of the water table throughout low-lying
landscapes in Interior Alaska, write the authors. A lowered water
table negatively affects the ability of wetlands to regulate climate
because it enhances the release of carbon dioxide by exposing soil
carbon to aerobic decomposition.
"Alaska is important in terms of waterfowl production and if you have
a lowering of the water table that could have a potentially huge
impact on waterfowl production," said Dave Verbyla, co-author and
professor in the School of Natural Resources and Agricultural
Sciences at UAF.
"This is an issue relevant to flyway management in terms of all the
waterfowl that might use the Yukon Flats National Wildlife Refuge and
overwinter elsewhere, and this is something that goes beyond the
refuges in Alaska," said A. David McGuire, co-author and professor of
ecology at the Institute of Arctic Biology at UAF.
National Wildlife Refuges cover more than 77 million acres in Alaska
and make up 81% of the national refuge system. These refuges provide
breeding habitat for millions of waterfowl and shorebirds that
overwinter in more southerly regions of North America.
"No one has done a state water-body inventory of this magnitude,"
said Brian Riordan, lead author and data manager for the Bonanza
Creek Long-Term Ecological Research program at UAF. "It will allow
land managers to stop speculating about possible water body loss and
begin to address the implications of this loss."
Using black and white aerial photographs from the 1950s, color
infrared aerial photographs from 1978-1982, and digital images from
the Landsat satellite from 1999-2002, Riordan outlined each pond by
hand. "With automated classification your accuracy goes down,"
Riordan said. Cloud shadows can look like water and Alaska rarely
experiences a cloudless day, said Verbyla.
The most difficult part of the four-year project, said Riordan, was
"having the patience to circle 10,000 ponds for each time period."
The main study area was the subarctic boreal region of Interior
Alaska, which spans more than 5 million square kilometers bounded on
the north by the Brooks Range and on the south by the Alaska Range.
To contrast the semi-arid, subarctic sites of discontinuous
permafrost in Interior Alaska, the authors also selected a study area
in the Arctic Coastal Plain where the temperatures are much colder,
the growing season much shorter, and the permafrost is continuous,
and a more maritime site south of the Alaska Range.
All ponds in the study regions in subarctic Alaska showed a reduction
in area of between 4 and 31 percent, with most of the change
occurring since the 1970s. The ponds in the Arctic Coastal Plain
showed negligible change.
***
This project was funded through support from the National Aeronautics
and Space Administration Land Cover/Land Use Change Program and the
National Science Foundation and United States Department of
Agriculture jointly sponsored Bonanza Creek LTER program.
Contact:
Brian Riordan, data manager Bonanza Creek Long-Term Ecological
Research program, University of Alaska Fairbanks, 907.474.6364,
David Verbyla, professor, School of Natural Resources and
Agricultural Science, University of Alaska Fairbanks, 907-474-5553,
A. David McGuire, professor of landscape ecology, Institute of Arctic
Biology, assistant leader, Alaska Cooperative Fish and Wildlife
Research Unit, University of Alaska Fairbanks, 907-474-6242,
Marie Gilbert, public information officer, Institute of Arctic
Biology, University of Alaska Fairbanks, www.iab.uaf.edu,
907.474.7412, marie.gilbert@uaf.edu
Notes for Journalists:
Journalists (only) may obtain a PDF of this paper upon request to
Harvey Leifert, +1-202-777-7507, hleifert@agu.org. Include your name,
name of publication, phone, and email address. The paper and this
press release are not under embargo.
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