Glacier National Park
The geographic location of Waterton-Glacier on the 49th parallel and the narrowness of the Rocky Mountain chain at this point contribute to the diversity of the region's vegetation. Glacier is at the center of a botanical watershed, a point separating plant communities common to the south from those in the northern ranges. As a result, many species are at their extreme limits of distribution.
Also, due to the narrowness of the mountains at this location, the Continental Divide lies very close to the Great Plains allowing for expanses of prairie to exist within park boundaries. A strong Pacific Northwest Coastal influence can be found in the Lake McDonald Valley west of the Continental Divide where approximately 100 Pacific coast plant species have been identified.
Weather patterns contribute to this diversity of vegetation in Glacier. Of particular interest is the Inland Maritime Climate that prevails in some western valleys of Glacier. This is the eastern most penetration of this weather pattern, and it results in higher precipitation and moderate winter temperature. The Pacific Maritime influence has created opportunities for plant species more often associated with the coast to gain a foothold in the Lake McDonald valley on Glacier's west side. East of the mountains, continental air masses coming out of the Arctic dominate in the winter, with subzero temperatures being common. The eastern slopes are located in the mountains' rain shadow, resulting in decreased precipitation and drier growing conditions. Also, the eastern valleys are subject to high downslope winds in both the summer and winter. These winds have a marked drying effect on plant communities.
Waterton Lakes National Park
Many unusual plants in Waterton like beargrass, devil's club, Macloskey's violet and western trillium are more common west of the Continental Divide. This occurs because the prevailing Pacific weather systems spill over the divide, bringing moister conditions and windborne seeds to Waterton. It is no coincidence that Waterton has six different species of anemone or windflower, for wind is the prevalent influence in the park.
The combination of Waterton's geographic situation, its topography (mountain and prairie) and its mild, moist, windy climate has created a wide variety of growing conditions within a very small area. Geologically, the Waterton area was very close to the southern edge of the continental ice sheet, so that glacial refugia for plants ("refuges" for plants and seeds that were not covered with ice) were not far away. This resulted in the dispersion of a large number of species into the area as the ice melted back.
Last updated: February 24, 2015