Northern dunes not deserts
The Carcross Desert is a well-known feature in the southern Yukon, and many people stop to take a walk in the sweep of sand found just north of the community. But if you go exploring there, do not expect to find desert plants such as cactus or exotic succulents.
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The Carcross dunes, with Caribou Mountain in the background.
(photo: Bruce Bennett)
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Even though this area is commonly referred to as a desert, it is really part of a system of dunes with closer ties to landscapes from the end of the last ice age than to arid regions. Most, if not all, of the plants there would never survive in a real desert, and several of them are rare species even for this part of the world.
Carolyn Parker, a research assistant at the University of Alaska Museum Herbarium, has a special interest in northern dunes. While most of her research has been on the Great Kobuk Sand Dunes in northern Alaska, she has also visited the dunes outside of Carcross several times, and thinks that they are likely part of a system of dunes once found across northwestern North America.
A geomorphologist colleague thinks that the landscape in Kobuk was developed during the last ice age when it was part of the unglaciated region known as Beringia, a steppe-like landscape where the wind blew almost constantly, carrying sand to the river valleys where it formed extensive sand sheets and dunes.
Today active sand dunes are rare in the north, and many of the ancient dune systems are now covered by forest. While Parker has not had the chance to work with a geomorphologist in the Carcross dunes, she suspects that their history is probably similar to that of the Kobuk dunes.
The sand probably began to accumulate during the Pleistocene when large glacial lakes filled the river valleys in the southern Yukon. Today wind blowing across Lake Bennett is probably the main source of sand, and the most active dunes are found near the lake.
Huge sand flats are exposed at the edge of the lake when the water levels drop. Winds blowing from the southwest pick up the sand, spreading it as far as the slopes of Caribou Mountain.
For Parker, the unique assemblage of plants found in northern dunes is one of their most interesting features. In the Kobuk dunes she found everything from Lyme grass, usually found on the Alaskan coast, to moss campion, typically found in alpine areas. In low areas where water collects for part of the year, she even found wetland sedges surviving in the dunes.
One of the most interesting species in Carcross is also a sedge. Carex sabulosa, commonly known as Baikal sedge, is a showy Asian species found in only four other sites in North America. It is also found on the dunes near Kusawa Lake, but not in Kobuk.
In the Carcross dunes, Yukon lupine grows "like a weed," says Parker. This unusual species also grows in Kobuk, and Parker speculates that it could have migrated across the North during the ice age when active sand dunes and sandy habitats were more widespread.
A large dune system by Lake Athabasca in northern Saskatchewan reminds Parker of the Kobuk dunes as the vegetation is very similar. Closer to home, dune systems can also be found along Kusawa Lake and the Takhini River, around Atlin and between the Whitehorse sewage treatment plant and Swan Lake.
Parker tried to find out whether there might be similar dune areas in western Beringia, located in the Russian Far East, but she has not learned of any yet. But she says that active dunes come and go, and no one knows exactly why.
She points out that dunes now covered by forest could revert to active dunes if a forest fire sweeps through the area, clearing out the vegetation. Human traffic probably prevents plants from gaining more of a hold in the sandy areas along the Carcross Road.
Some people in Carcross told Parker that the dunes closer to the lake are more vegetated now than they were a few decades ago. The historic photographs that she has looked at seem to confirm this change.
Parker hopes that more work will be done in the Carcross dunes, and that a geomorphologist will have a chance to pin down dates for the formation of the features there.
"They are unique settings. Some people would say that we are looking at a little bit of the Pleistocene and I think that might be stretching it a bit, but I think that we are looking at landscapes at least partly representative of that era," she says.
For more information on northern dunes, contact Carolyn Parker at fnclp1@aurora.uaf.edu.
