for National Geographic News
Thousands of Alaska's lakes have shrunk and many others have dried up over the past 50 years, scientists have discovered.
During this period the 49th U.S. state has been experiencing a steady warming trend, which suggests that global climate change will continue to shrink lakes that are critical habitat for millions of migratory waterfowl.
In a new study published last week in the Journal of Geophysical Research - Biogeosciences, researchers from the University of Alaska, Fairbanks, compared modern satellite photos to aerial photos from the 1950s.
The scientists also examined another set of aerial photos taken between 1978 and 1982.
The photos document changes in water levels in nine lake-strewn tracts ranging from the shores of the Arctic Ocean to Talkeetna, a region not far north of Anchorage (Alaska map).
The biggest changes, the study revealed, occurred in interior Alaska's boreal forest, which sprawls across two million square miles (five million square kilometers), says Brian Riordan, lead author of the study.
In this region, Riordan says, lakes have shrunk by 14 to 31 percent.
In the colder reaches of the Arctic and in Talkeetna, which enjoys a cooler maritime climate, there was very little change.
The team's findings document a trend that has also been observed by Native Americans.
"When I started the project, there was much speculation," Riordan said. "You would have village elders saying, My family's hunted ducks at this pond for 150 years, and in the past 20 years the shore has been receding each year.
"One of the most important results from our study is to put a number to it," Riordan said.
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