Robert G. Bailey

Delineation of ecosystem regions

As a means of developing reliable estimates of ecosystem productivity, ecosystem classification needs to be placed within a geographical framework of regions or zones. This paper explains the basis for the regions delineated on the 1976 mapEcoregions of the United States. Four ecological levels are discussed—domain, division, province, and section—based on climatic and vegetational criteria. Statistical tests are needed to verify and refine map units.

Ecological regionalization in Canada and the United States

Abstract Present interest in environmental problems which are international, interstate or interprovincial in scope is drawing attention to the necessity for ecological regionalizations that will serve as a basis for intraregional transfer of experience. The major efforts at ecological regionalization by the national governmental agencies are described and compared. Although similar concepts have evolved in both countries, different systems of units have been developed for defining and mapping ecosystems at the regional scale. Before any regionalization is used it should be thoroughly tested, and modified if necessary.

Suggested hierarchy of criteria for multi-scale ecosystem mapping

Abstract Ecological units of different size suited to the kinds of questions being asked at different levels of management decisions need to be identified and mapped. A set of criteria for sub-dividing a landscape into ecosystems of different size is presented, based on differences in factors important in controlling ecosystem size at varying scales in a hierarchy.

The factor of scale in ecosystem mapping

Ecosystems come in many scales or relative sizes. The relationships between an ecosystem at one scale and ecosystems at smaller or larger scales must be examined in order to predict the effects of management prescriptions on resource outputs. A disturbance to an ecosystem may affect smaller component ecosystems, which are encompassed in larger systems that control the operation of the smaller systems. Environmental factors important in controlling ecosystem size change in nature with the scale of observation. This article reviews those environmental factors that are thought to be useful in recognizing and mapping ecosystems at various scales.

Problems with using overlay mapping for planning and their implications for geographic information systems

As part of the planning process, maps of natural factors are often superimposed in order to identify areas which are suitable or unsuitable for a particular type of resource management. Overlay maps may also be used to identify analysis areas for predictive modeling of resource productivity and ecological response to management. Current interest in applying computer-assisted mapping technology to making overlay maps is drawing attention to geographic information systems for this purpose. The resultant maps, however, may be so inaccurate or unable to capture significant units of productivity and ecological response that they could lead to imperfect or false conclusions. Recommendations are made on how to proceed in light of these problems.

Continental Types and Their Controls

The ecoregions on the Earth’s land masses are arranged in predictable patterns and are causally related to macroclimate, i.e., the climate that lies just above the local modifying irregularities of landform and vegetation. These macroclimates are regularly arranged with reference to several controlling factors.

Mesoscale: Landform Differentiation (Landscape Mosaics)

Macroclimate accounts for the largest share of systematic environmental variation at the macroscale or regional level. Within the same macroclimate, broad-scale landforms break up the east–west climatic pattern that would occur otherwise and provide a basis for further differentiation of ecosystems—the landscape mosaics mentioned earlier. The character of a landscape mosaic with identical geology will vary by the climatic zone. For example, vertical limestone would form quite different landscapes in a subarctic climate than in a hot and arid climate.

Microscale: Edaphic-Topoclimatic Differentiation (Sites)

We may subdivide landscape mosaics into smaller ecosystems called sites or microecosystems. At this point, we turn our attention to the component parts of these mosaics. These are minor in the sense of geographic scale but may play a decisive role in determining the land use.

Ecoclimatic Zones of the Earth

The effects of latitude, continental position, and elevation, together with other climatic factors, combine to form the world’s ecoclimatic zones, herein referred to as an ecosystem region, or ecoregion. Figure 5.17 shows the climatic zones where we might expect distinct ecosystem assemblages to occur. This map shows climatic units that are important to the climatologist and can be used to help determine ecosystem boundaries at the macroscale. Criteria for refining and delineating these zones, or ecoregions, at several levels of detail are presented below.

Role of Climate in Ecosystem Differentiation

Climate is the composite, long-term, or generally prevailing weather of a region. As a source of energy and water, it acts as the primary control for ecosystem distribution (Figure 4.1).