Reviews of the history and the applications of ecological regionalization in Canada are given by Bailey et al. (1985), Rubec et al. (1988), Ironside (1989), Rowe (1992), Rubec (1992), Marshall et al. (1992), Wiken and Lawton (1995), and Marshall et al. (In press). These overviews and documents show a steady progress towards developing a broadly based ecosystem perspective.
The Canada Committee on Ecological Land Classification (CCELC) was created in 1976 to provide a national forum to encourage the development, both of a uniform national ecological approach to terrestrial ecosystem classification and mapping, and of a sound application of the ecological approach to sustainable resource management and planning. The objective of the approach is to delineate, classify, and describe ecologically distinct areas of the earth's surface at different levels of generalization using various abiotic and biotic factors at each of the levels (Rowe and Sheard 1981;Wiken 1986). The ecological units are defined through the spatial differences in a combination of these factors. The dominance of any one or more of these factors will vary from one place to another. Between 1976 and the mid 1980s a CCELC hierarchical classification evolved with seven levels of generalization. From the broadest to the smallest, they are: ecozones, ecoprovinces, ecoregions, ecodistricts, ecosections, ecosites and ecoelements (Environmental Conservation Service Task Force 1981;Rowe and Sheard 1981;Wiken 1979,1986;Ironside 1991).
Following the establishment of the CCELC classification framework, and benefiting from previous published scientific reports and maps at various scales, several syntheses of ecological (biophysical) land classification information at the national level were produced. In 1986 a map and report describing terrestrial ecozones (Wiken 1986) was published. In describing ecoregionalization Wiken (1986) stated:
"Ecological land classification is a process of delineating and classifying ecologically distinctive areas of the surface. Each area can be viewed as a discrete system which has resulted from the mesh and interplay of the geologic, landform, soil, vegetative, climatic, wildlife, water and human factors which may be present. The dominance of any one or more of these factors varies with the given ecological land unit. This holistic approach to land classification can be applied incrementally on a scale-related basis from site-specific ecosystems to very broad ecosystems."
In essence, the individual areas delineated on the earth's surface (i.e. ecozones, ecoprovinces, ecoregions, ecodistricts, etc.) gain their identity through spatial differences in a combination of landscape characteristics. The factors that are important vary from one place to another at all scales. By extending this approach to mapping, a provisional ecoregion map of Canada was produced in 1987 and was eventually published by the National Atlas of Canada (Wiken et al. 1993). This map included the first national approximation of ecozones, ecoprovinces, and ecoregions.
As well, working groups of the CCELC published related thematic studies such as the Wetland Regions of Canada (National Wetlands Working Group 1986) and Ecoclimatic Regions of Canada (Ecoregions Working Group 1989) to provide a specific focus on certain ecosystems or their component parts. The wetland regions represented areas within which similar and characteristic wetlands develop in locations that have similar topography, hydrology, and nutrient regimes. Subdivisions of the wetland regions are based on the distribution and relative abundance of the various kinds of wetlands. In contrast, the ecoclimatic regions recognize areas by emphasizing the roles and influences that climate has had in molding the patterns and inherent qualities of ecosystems. It chose gradients of ecologically effective macroclimate (as expressed by vegetation and soil development) as the defining criteria.
While it was recognized that the levels of generalization as developed by CCELC were conceptually sound, the spatial units which had been proposed (terrestrial ecozones, ecoregions, and ecodistricts) needed updating to reflect new information. The revised material would continue to serve monitoring and reporting needs at regional, national, and international levels. Specifically, in order for the framework to be used effectively, it was necessary that it:
- be revised in further consultation with the federal, provincial and territorial agencies with environmental resource management responsibilities across the country;
- reflects and relates to the latest efforts in regional ecological classification and mapping;
- provides links to other biophysical and socioeconomic databases, for example the Soil Landscapes of Canada (Shields et al. 1991) and population statistics (Government of Canada 1996);
- includes descriptions of ecozones and ecoregions in an easily retrievable format; and
- be supported by a data model that relates information between different levels of the framework and facilitates linking to external data sources.
To achieve this, a collaborative project was initiated in late 1991 between Environment Canada (State of the Environment Directorate), Agriculture and Agri-Food Canada (Centre for Land and Biological Resources Research) and Natural Resources Canada (Canadian Forestry Service). Project members (the Ecological Stratification Working Group), in consultation with provincial/territorial agencies, revised map unit boundaries and compiled attribute data about key levels of the terrestrial component of the national ecological framework.