Carcross Dunes are a result of a glacial process. About 10,000 years ago, the great ice sheets that covered much of North America were melting. Ice dams created a series of glacial lakes that submerged some valleys under 300 metres of melt water. A layer of sand and silt, which had been trapped in the glaciers, settled to the bottom of these lakes in a thick layer.

The Watson River cut through the lake bottom sediments and continues to bring sand and silt into Bennett Lake. This constant supply of sand makes the Carcross Dunes a truly dynamic system. In the spring, low water-levels expose the sand deposits and the prevailing winds blow the sand onto the beach and into the dunes.

Sometimes the wind blows the vegetation away and digs holes (blowouts) in the sandy landscape. Old forest, previously buried, is sometimes re-exposed. To the north east, the Carcross Dunes climb up onto a low ridge below Caribou Mountain.

The dunes habitat is home to some rare plants and insects.

Ten or more species of insects found in the Carcross Dunes are found in few other places on earth. Scientists studying the dunes have found eight species of insects that may be new to science.

The Coast Dart Moth (Euxoa cursoria) is found in the dunes of Europe and Asia, Carcross and Athabasca (Alberta). Their larvae are cutworms that feed on the roots of a variety of dune plants.

There are only six Baikal sedge (Carex sabulosa) populations in Yukon, one in Alaska, and another in Asia. This species has been listed as “threatened” under the federal Species at Risk Act.

Siberian asters (Aster sibiricus) are abundant in some of the most active portions of the sand dunes. Their decaying leaves contribute nutrients to the developing soil.

The Dune Tachinid Fly (Germaria angustata) and other rare insects can be found at the edge of the Carcross Desert. In July, you might see a female Dune Tachinid Fly looking for a place to lay her eggs. She will try and put them where they can hatch and attack a host caterpillar, perhaps a larva of the Coast Dart Moth. The Dune Tachinid Fly is difficult to distinguish from other blackish flies that hover over the dunes.

The genus Gnorimoschema, in the sub-family Gelechiidae, is a very diverse group of small moths which predominantly inhabit dry or arid places in the northern hemisphere. Five new species of Gnorimoschema were identified here in the 1980s and have not been scientifically described or named. Although winged and fully capable of flight, they often run, hop and flutter across their sandy home. At rest, their colouration makes them blend with the sand and difficult to see.

The Yukon Lupine (Lupinus kuschei) is a rare species of lupine that evolved in the dunes of Yukon and Alaska.

Source: Yukon Government