Ministry of Environment Ecology

PART I
Ecoregion Classification Background

Introduction

British Columbia has many ecosystems due to its varied physiography and climates. It is located at mid-to northerly latitudes and is bounded on the west by oceanic influences of the northern Pacific Ocean and on the east by continental climates of the Interior Plains and Rocky Mountains. Its varied geological history has resulted in a complex topography. In addition, the Province has had a complex climatic history . Current climatic patterns are varied but, most typically, the Province is dominated by moist, cool to cold,temperate climates in a mountainous setting, most of which is higher than 1000 metres above sea level. The plants and animals of the Province are affected by that environment and also by historic factors such as the position of glaciers or other barriers to dispersal and migration.

An Ecoregion classification was developed in order to provide a systematic view of the small scale ecological relationships in the Province. This classification is based on climatic processes and landforms, and it brings into focus the extent of critical habitats and their relationship with adjacent areas. The Ecoregion Classification system was adopted by the Wildlife Branch in 1985 to serve as a framework for recognizing small scale ecosystems in British Columbia (Demarchi 1988a). The Ecoregion classification helps us understand and to depict the great habitat diversity of the Province. Since 1985, the Ecoregion Classification has been revised 3 times to reflect more detailed mapping (Demarchi 1988b, 1993, 1995). The overview map, presented at 1:2,000,000, was mapped using 1:250,000 Landsat, topographic, biogeoclimatic and oceanographic data.

Most British Columbians have an intuitive feeling for the Province’s regional ecosystems. People from the Interior often travel to the "Coast" to do their shopping. You hear other expressions such as "up north" for anything north of Quesnel, the "Peace River" and the "Cariboo". These are not imaginary places or strictly administrative areas: they have their basis in an Ecoregion framework. For example "up north" is really those cold mountains, plains and plateaus which are usually under the influence of a cold Arctic air mass during the winter; the "Peace River" is the area of deep soil that occurs in the Alberta Plateau portion of British Columbia ; and the "Cariboo" is an area of rolling hills that are interspersed with wetlands, aspen groves and stunted Douglas-fir forests, and which lies between the area of hot-dry summers to the south and the area of sub-Boreal forests to the north. But these are unstructured classifications with poorly defined boundaries, little or no reference to scale and an unlimited number of possible units. While classifications do not have to be unnecessarily complicated, they must be usable. If they serve several users, then so much the better.

The Ecoregion Classification system is used to stratify British Columbia’s terrestrial and marine ecosystem complexity into discrete geographical units at five different levels. The two highest levels, Ecodomains and Ecodivisions, are very broad and place British Columbia globally. The three lowest levels, Ecoprovinces, Ecoregions, and Ecosections, are progressively more detailed and narrow in scope and relate segments of the Province to one another. They describe areas of similar climate, physiography, oceanography, hydrology, vegetation, and wildlife potential.

Within each terrestrial ecoregion, climatic zones occur where specific soils, plant and animal communities and aquatic systems develop because of the interaction of climate with the land surface and surfical materials. These zones are best defined within the Biogeoclimatic Ecosystem Classification system. Ecological zones in marine ecosystems are products of temperature, salinity, sea-bed configuration, wave energy, and water depth.

Each ecosystem is ultimately identified by sampling individual sites. At the lowest level in an ecosystem classification, attention is divided among specific parameters, such as: topography, surficial materials, soil development, moisture regime, microclimate, floristics, succession, productivity, and animal use for terrestrial environments; or, bathymetry, substrate, morphology, currents, water chemistry and animal use for aquatic environments.

Ecoregions should be thought of as ‘big picture’ ecosystems. As such the classification hierarchy should be viewed for its big, all inclusive landscape definitions, then progressively though more detailed levels, and finally at the lowest level other classifications need to be brought into play for the definitions of local ecosystems. The boundaries on Ecoregion/Biogeoclimatic/Biophysical Habitat maps must be thought of in the same way, broad lines for small scale ecosystems progressing to greater precision for the larger scale ecosystems. For convenience, however, one boundary is used to define all ecosystem levels, from the Ecodomain down through the Biogeoclimatic/marine zone to the Biophysical Habitat Unit level.

• Next Page