ANCHORAGE, Alaska – Warming temperatures over the past half-century have been slowly drying out the Kenai Peninsula, transforming wetlands into forests and shrinking ponds, according to a study that analyzed vegetation change at more than 1,100 locations.
The loss of wetlands could reduce bird-nesting habitat, and the expansion of woody growth into wet areas could increase the danger from wildfires, said biologist Eric Klein, lead author of a paper published this August in the Canadian Journal of Forest Research.
“You’re getting rid of these natural breaks,” Klein said. “It becomes quicker and easier for wildfires to spread.”
The study found that wooded areas in the Kenai National Wildlife Refuge had grown dramatically since 1950, expanding from 57 percent to 73 percent of the land. Wetlands shrank, from covering about 5 percent to less than 1 percent.
Many lakes lost volume too, especially small, isolated “kettle lakes” that have existed since the ice age ended 8,000 to 12,000 years ago.
“It seems like that there is an environmental shift taking place,” said Klein, who conducted the research for his master’s degree in environmental science at Alaska Pacific University. “This is just one more piece of the puzzle.”
Global air temperature has risen at least 1 degree Fahrenheit over the past century, but some areas of the Arctic have warmed much faster. Many scientists believe that increases in human-produced greenhouse gases have helped drive the warming, in addition to complex natural cycles.
Effects accelerating
Whatever the causes, the effects have been accelerating. Every decade has brought spring green-up about 2.3 days sooner and pulled the ranges of animals and plants about four miles farther north. Recent scientific papers have documented the invasion of shrubs into North Slope tundra, while spruce forests in the Interior have declined because of summer droughts. Last year’s Arctic Climate Impact Assessment cited forest fires and the Kenai’s beetle epidemic as further evidence of climate change.
On the Kenai, average air temperatures have risen about 1.2 degrees Fahrenheit over the past 30 years, allowing dwarf birch, blueberries and black spruce to colonize bogs that existed intact since glaciers retreated up to 12,000 years ago, according to co-author Ed Berg, an ecologist with the U.S. Fish and Wildlife Service.
“When you dig down into the peat, you don’t see any stems or shrubs,” Berg said in a statement about the research. “Had they grown there in the past, they would have been preserved.”
Klein, now a staff biologist for an Anchorage environmental engineering firm, launched the study in 2003 with help from Berg in the field and help with the analysis from Alaska Pacific University biology professor Roman Dial. The three scientists completed “Wetland Drying and Succession Across the Kenai Peninsula Lowlands” last fall.
Changing landscape
Using aerial photographs taken in 1950, Klein examined 1,113 locations chosen at random across about 546,000 acres in three broad areas of the Kenai wildlife refuge. At the time, more than half were forested, with 31 percent open land, 5 percent swampy and 7 percent ponds or small lakes.
When Klein located the same spots on photos taken in 1996, he discovered that a remarkable shift had taken place. Forest had grown, while open land and lakes had shrunk. The area covered by swamps and bogs had almost disappeared. Burned and unburned areas changed about the same.
Klein also visited 84 sites in the field with Berg and several technicians, spending much of the summer of 2003 thrashing through Kenai backcountry, examining firsthand how the land had changed.
“The bugs were horrible,” he said. “There were some places where you could only write if you had a head net on, and that was after you covered yourself in Deet.”
Klein documented many lakes and ponds with expanding aprons of vegetation, with new bushes and trees lurking at the fringes. One pond was especially dramatic, completely swallowed by successive bands of invading plants.
On the 1950 aerial photo, it had stretched 100 feet across.
“When we got to the site, and there was no water left at all,” Klein said, “you could see these very distinct bands (of vegetation), almost like a bull’s-eye on a dart board, extending from the center out.”
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