ENVIRONMENTAL HISTORY
Richard Hebda
Botany and Earth History
Royal British Columbia Museum
PO Box 9815 Station Provincial Government
Victoria, B.C.
V8W 9W2
and
Biology and School of Earth and Ocean Sciences
University of Victoria
PO Box 1700
Victoria, B.C.
V8W 2Y2
INTRODUCTION
The Montane Cordillera Ecozone's environmental history is complicated and poorly known largely because the region comprises the most complex biophysical setting in Canada.
The region's irregular topography ranges from deeply incised valley bottoms in the south to Canada's highest peaks immediately adjacent to the east and west. In the north, medium to high elevation plateaux are punctuated by mountain masses and bordered by continental mountain chains on both east and west sides (Holland 1976).
Three broad climatic trends are superimposed upon this landscape resulting in a bewildering array of poorly described subregional and local climates (Pojar and Meidinger 1991). First, mean annual temperatures decrease northward across the 7-8 degrees of latitude occupied by the zone. Second, the climate becomes progressively more continental along a gradient from the ocean-ward margin of the zone to the Rocky Mountains on the east. Extensive north-south dry belts occur in the east-facing lee of the Coast-Cascade Mountain system. Third, temperatures cool with elevation from hot valley bottoms to frigid mountain tops. Precipitation also increases with elevation though declining near peaks.
The zone's flora and fauna are of diverse origins spreading after deglaciation from southern arid regions, mild coastal lands in the west, cold landscapes to the north, and the interior of the continent to the east and southeast. This biotic diversity, when combined with the physical diversity of the region, has resulted in the ecologically most complex region of Canada. What we know of the region's environmental history helps understand how this diversity arose, provides insight into basic long term ecological processes and explains the distribution of ecosystems and species we see today.
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