Scientists have found that more than 10,000 of the Alaska's lakes have shrunk or dried up over the past 52 years. Since 1950 Alaska has been experiencing a steady warming trend, increased thawing of permafrost and greater water loss through evaporation of open waters.
A team at University of Alaska, Fairbanks, compared modern satellite photos to aerial photos from the 1950s, 1978 and 1982. The scientists counted for changes in water levels in nine tracts ranging from the shores of the Arctic Ocean to Talkeetna, close of Anchorage. "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, researcher at the University of Alaska Fairbanks. "In this region lakes have shrunk by 14 to 31 percent" and most changes occurred during the 1970's.
In the coastal sea, buffed areas and Arctic colder regions the change was insignificant. The changes found by scientists have already been noticed 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. "
"No one has done a state water-body inventory of this magnitude," said Riordan.
"It will allow land managers to stop speculating about possible water-body loss and begin to address the implications of this loss."
Interior Alaska is particularly vulnerable to drying lakes "because it's a semi-arid region with extremely cold winters and relatively warm, dry summers," says David Verbyla, also from University of Alaska, Fairbanks.
Precise mechanisms that lead to this phenomenon are still unknown. "It's probably a combination of factors," Verbyla says. "One is that the permafrost [in this region] is thin and discontinuous."
"As global warming makes that permafrost even thinner," he said, "you could basically have leaks through [it] and lake water would sink far below ground".
"Another possibility is that warmer, longer summers are triggering more evaporation," he says.
Some say that climate warming could accelerate the rate at which marsh plants (like cattails, bulrushes, and sedges) invade open waters and convert them to meadows. "Increased forest fires could also play a role," Verbyla says.
Forest fires burn the layer of organic matter on the top of the soil, exposing it and decreasing its ability to insulate the permafrost from summer warm. "Up to 25 percent of the acreage in some areas has burned in the past 50 years," Verbyla says. "2004 was our biggest fire year ever. … Wildfire is a big deal in the boreal forest."
A lowering of the water table in the low altitudes is also suspected. Wetlands present a great diversity of plant and animal life. "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 Verbyla.
Alaska's stagnant waters environment offers for native villages activities like fishing or moose and bird-hunting areas. "In a lot of villages, spring duck hunting is a major subsistence activity," Verbyla said.
Some villages gain money by offering guided tours for visiting hunters. "In addition, he notes, Alaska law grants water rights to the native villages."
"What happens when the water they were given is reduced by 30 percent?" he asks. "Are they entitled to more acreage?"
The changes in hydrology of the lakes will produce shifts in the ecosystems. Dabbling ducks (like mallards, wigeons, teals, pintails, shovelers) might be favored by the new conditions to the disadvantage of the diving ducks (like pochards and scaups), which prefer deep water. "It could be beneficial to some species and detrimental to others," Verbyla said.
"I've seen a lot of fluctuation in water levels over the years," says Mark Bertram, a wildlife biologist from the U.S. Fish and Wildlife Service's Yukon Flats National Wildlife Refuge.
"There are obviously wetlands that are actively drying up, but I've also observed quite a few water bodies that are flooded that weren't flooded 13 years ago."
But Bertram agreed - despite this - that interior Alaska is drying.
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