National Ecological Framework (2 of 23)

Attribute Data Report



Since the late 1960s, governments, non-government groups, universities and industry have worked to develop a common, hierarchical ecosystem framework and terminology. It gained momentum in the 1970s, especially following the creation of the Canada Committee on Ecological Land Classification.

In 1991 a collaborative project was undertaken by a number of federal agencies in cooperation with provincial and territorial governments, all under the auspices of the Ecological Stratification Working Group, to revise previous work and establish a common ecological framework for Canada. The working group focused on three priority levels of stratification, namely ecozones, ecoregions, and ecodistricts.

The underlying principle for the initiative was the commitment and need to think, plan, and act in terms of ecosystems. The principle required people to move away from an emphasis on individual elements that comprise an ecosystem to a perspective that is more comprehensive - a holistic approach. This required an national ecological framework to provide a consistent, national spatial context within which ecosystems at various levels of generalization can be described, monitored, and reported on. The use of such a framework of standard ecological units provides for common communication and reporting between different jurisdictions and disciplines. In this case, the immediate requirement was to provide a common ground to report on the state of the environment and the sustainability of ecosystems in Canada. The concepts and hierarchy for ecological classification set out by the Canada Committee on Ecological Classification in the 1970s and 1980s (Ecological Stratification Working Group 1996, Ironside 1991) were the overall guide for the revised national framework.

The resulting national report "A National Ecological Framework for Canada" released by the Ecological Stratification Working Group in 1996 describes the methodology used to construct the ecological framework maps, the concepts of the hierarchical levels of generalization, narrative descriptions of each ecozone and ecoregion, their linkages to various data sources, examples of applications of the framework, and a list of contributors and collaborating agencies.

Although a set of six regional ecodistrict maps covering all of Canada were produced separately, no descriptions of the ecodistricts accompanied the maps (Ecological Stratification Working Group, 1995). Only a limited attribute database was prepared to accompany the maps in the time available (Selby and Santry, 1996).

Recent developments

Subsequent to the release of the main report in 1996, a number of new materials associated with the framework have been published providing broader, in depth studies and data, ranging from provincial, through national, to North American continental perspectives. These include:

  • the 1996 Ecoregions of British Columbia (revised 4th edition).
  • the 1998 Ecoregions of Saskatchewan;
  • the 1998 Terrestrial Ecozones, Ecoregions and Ecodistricts of Manitoba, An Ecological Stratification of Manitobas Natural Landscapes;
  • the 1999 Ecoregions and ecodistricts of Nova Scotia
  • the 1996 A Perspective on Canadas Ecosystems by the Canadian Council on Ecological Areas (CCEA), which provides a country wide, in-depth description of Canadas terrestrial ecozones; and
  • the 1997 Ecological Regions of North America, Towards a Common Perspective by the NAFTA Commission for Environmental Cooperation (CEC), provides the integrated, continental perspective.

In the course of developing the North American perspective, an ecoprovince level of generalization, between ecozone and ecoregion, was compiled for the Canadian framework (Marshall et. al. 1998). In 1999, a revised and expanded attribute database (the subject of this report), replaced the earlier version (Selby and Santry, 1996). It includes attribute data for the ecoprovince level of generalization.

Ecological land classification

Ecological land classification is:

"a process of delineating and classifying ecologically distinctive areas of the Earths 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 a number of these factors varies with the given ecological land unit. The holistic approach to land classification can be applied incrementally on a scale-related basis from site-specific ecosystems to very broad ecosystems" (Wiken 1986).

The fundamental basis for delineation of ecological units is to capture the major ecological composition and the linkages between the various components (e.g., landforms, soils, water, and vegetation) rather than treating each component as a separate characteristic of the landscape.

Key points in the application of ecological land classification in delineating ecological map units are identified in the box below (Commission for Environmental Cooperation, 1997; Wiken and Gauthier, 1996).

Key points in ecological land classification

  • Ecological Land Classification incorporates all major components of ecosystems: air, water, land, and biota, including humans.
  • It is holistic; "the sum is greater than the whole".
  • The number and relative importance of factors helpful in delineating ecological units varies from one area to another, regardless of the level of generalization.
  • It is based on a hierarchy with ecosystems nested within ecosystems.
  • It involves integration of knowledge and is not simply an overlay process.
  • It recognizes that ecosystems are interactive and that characteristics of one ecosystem blend with those of another. 
  • It recognizes that map lines generally depict the location of zones of transition.

Ecosystems are numerous and complex. The challenge is to make the ecological map units workable and understandable to reflect this complexity. It is equally important to recognize that while ecological land classification is science-based, it is also an art in the sense that ecological cycles, characteristics and interactions are not always readily apparent or measured and therefore need to be interpreted from the development of vegetation, soil, and landform characteristics or other factors.

Ecosystems not only vary tremendously, but form part of a "nested hierarchy" at multiple scales, in which smaller ecosystems are encompassed within successively larger ones. A hierarchical system permits the choice of detail that suits management objectives and the proposed use. Because management and other decision-making deal at various levels, from local to regional to national and even to international, one of the prerequisites of ecological land classification is to portray ecosystems at a level, scale, and intensity appropriate to the need.

Although the ecosystem concept implies equality among components (soils, climate, vegetation, etc.), all components may not be equally significant throughout the hierarchy (i.e., some can be more determinant or enduring than others). The dominance or importance of any one factor may vary considerably in defining the spatial expression of an ecosystem at each level of generalization. Ideally, differentiating criteria are based on enduring components of the ecosystem and are those that do not change perceptibly over time, such as geology, surficial materials, landform, and waterbodies. For any level of generalization the pattern of components may vary from one ecological unit to the next, as do their relationships and processes. For example, in northern Ontario ecosystems are controlled by the bedrock of the Canadian shield, shallow soils, and multiple lakes, whereas, southern Ontario exhibits flat sedimentary bedrock, buried by deep soils and fewer lakes.These factors influence other conditions such as habitat, vegetation growth, and productivity.

Although the basis for delineating individual ecological map units is to capture the major ecological components and the relationships between each component, it is essential to capture their relative abundance and pattern. Abundance refers to the relative quantities of components associated with each map unit and pattern concerns the arrangement of components vertically or horizontally. This process is directly opposed to traditional sector resource mapping as singular and independent items. Sector classifications are well suited for specific purposes and have been designed to meet focused needs. They have limitations, however, for state of environment and resource sustainability reporting which must consider linkages between issues and among the various components of the ecosystem. However, ecological classification, for a given level of generalization, gives up specific detail found in single sector surveys (e.g. forestry) in favor of more general data from several sectors.

The actual process of capturing ecosystems in map format is not an easy task. Ecosystems are by their nature very dynamic and interact with other ecosystems. They do not have discrete boundaries. The challenge is to depict the complexity of ecosystems through appropriate map units. Establishing ecosystem boundaries on a map involves distinguishing those systems in which structures exhibit a consistent or significant degree of change when compared to adjacent systems. Since land classification is based on multiple factors, the key to placing boundaries on an ecological map is an understanding of genetic processes (how it originated) and an understanding of the causes of the differences between classified units as opposed to the effects. For example, the boundary between the Cape Breton Barrens ecodistrict and the adjacent Cape Breton Plateau ecodistrict is due primarily to the lack of vegetation caused by exposure to extreme climatic conditions and shallow soil. Landform, and landform pattern with its geologic substrate and surface shape and relief are also important criteria for establishing boundaries at the meso-scale (ecoregions and ecodistricts). For example, the drumlinized till plain of the Lunenburg Drumlins ecodistrict separates it from the more subdued topography and associated expansive wetlands of the adjacent Rossignol ecodistrict (Webb and Marshall, 1999).

Ecosystems can range from natural systems through to those heavily modified by human activity, such as urbanization. Land use and other human factors can influence character and the delineation of some types of ecosystems. In some situations human activities have historically been pervasive, significantly influencing the ecological processes and character of a region. For example, the permanent influence of agriculture on the grasslands of the Prairie Provinces in western Canada, or urban development and agriculture on the Carolinian forests of southern Ontario. Ideally, the boundaries reflect factors that control ecosystems distribution at various scales, such that they can be recognized, compared, and applied regardless of human activities and other natural disturbances.