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. “ “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 National
Wildlife Refuges cover more than 77 million acres
in “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 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 sub-arctic 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 All
ponds in the study regions in sub-arctic ##
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