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I've just returned from a trip out to the west coast. Not having spent a lot of time on the far side of the divide, I was amazed at the number of changes that occur as one traverses from the Eastern to the Western Slopes.

The Rockies provide an effective barrier to weather patterns moving in from the Pacific coast, giving Alberta a very different climate from its western neighbour. As storms move inland from Vancouver, they come up against an impenetrable obstacle--the mountains. Climbing upward to move over this huge piece of rock, the air temperature rapidly cools with the steady rise in eleva-tion. Since warm clouds can hold more moisture than cold ones, they drop much of their rain and snow long before reaching the continental divide. I guest that's why they say in Vancouver you don't tan--you rust!

Annual rainfall is often one of the most important factors in determining which plants and animals will be found in a particular area. The town of Banff receives an average of 471 mm of precipitation each year compared with 477 in Golden and a whopping 1064 in Revelstoke. Golden forms the western boundary of an area known as the Columbia Forest while Revelstoke is at its heart and receives more than twice the annual moisture of either Banff or Golden. The Columbia Mountains are very wet and provide conditions for growth similar to the Coastal Range. As a result, the Columbia forest also contains many of the same species. The more than ample rainfall received in this area causes a lush, rain forest environment in British Columbia while Alberta displays a drier spruce/pine forest.

Leaving Canmore and heading west, the change is a gradual one. You begin by driving toward Lake Louise and the B.C. border through a forest comprise primarily of lodgepole pine and spruce. As you pass Golden, you enter the Columbia Forest and this is where the changes really begin to reveal themselves. By the time you get to Glacier and Revelstoke National Parks, trees unknown to Alberta have appeared; trees like the Western Red Cedar and the Western Hemlock. Both these trees need large amounts of moisture to survive and the western slopes provide just that. They also have very important historical ties as it was these Cedars that were used to carve the huge totem poles and dug out canoes of the west coast Indians. Today, the cedars are used extensively by B.C.'s cedar shake industry and the hemlock is one of the most important trees to the provinces logging industry. As a result they have been heavily logged leaving the provinces national and provincial parks to provide some of the few refuges of large undisturbed stands.

Other representatives of the Columbia Forest include the Interior Douglas fir, western white pine, western larch, grand fir and the western yew. Unlike the very open floor typical of the lodgepole pine forests around Canmore, the Columbia forest floor is very dense with ferns and other plants like the thim-bleberry. It's hard to believe that so much diversity can occur over such short distances. The next time you head west, keep your eyes out for some of the many changes through the ranges.