The Natural Heritage Reference Manual (OMNR 1999) outlines a Natural Heritage System approach. This approach is a useful method for the protection of specific natural heritage features and areas because it reinforces an understanding that individual areas and features have strong ecological ties to other physical features and areas in the overall landscape. When addressing the significant wildlife habitat feature of this system, it is important to consider significant wildlife habitat at more than one scale. Some habitats may be of national or provincial importance, such as an important migration stopover site for migrating birds (e.g. RAMSAR sites–Appendix A). Other habitats may be locally significant, such as a winter concentration area for a local population of deer. Generally, those habitats that are significant at larger scales are considered to be of greater significance than those at the local scale. That does not imply that significance at the local level is not important, as it can be very important. However, scale is a very important criterion when ranking significance between two or more potential sites.

Landscapes are relatively large geographic areas. From an ecological perspective, landscape boundaries are most appropriately defined based on climatic considerations and physiography. These are the two main ecological features used to identify ecological units known as site regions. At a finer scale, vegetation responses to climate and physiography are the primary factors used to define site districts. Hills (1959) divided the province into 14 site regions and 67 site districts (Figure 2-1). The ecosystems that occur in a given site district are distinct from those in other site districts with respect to climate, landform, and patterns of vegetation. For more information on site regions and site districts of Ontario (Figure 2-1), refer to a Framework for the Conservation of Ontario’s Biological Heritage (Beechey 1980). The Ontario Ministry of Natural Resources (OMNR) has used these ecological units as the basis for determining representation of potential Areas of Natural and Scientific Interest (ANSIs), wetland rarity in the provincial wetland evaluation system, and for determining the rarity of species and vegetation communities across the province. Planning authorities can also use these units as a basis for making landscape level decisions with respect to significance. Other criteria can be used to define landscape boundaries, such as watersheds, sub-watersheds, regional municipalities, and counties. Landscapes that only consider the smaller scales are not as ecologically sound as large-scale landscapes in natural heritage planning. Many significant features extend beyond administrative boundaries and certainly, wildlife is not confined by these boundaries. Planning authorities have to make planning policies for land within their jurisdiction. Ideally, a Natural Heritage System for a planning area would incorporate a variety of scales from global to local and these would be taken into account during the planning process.

Figure 2-1. Hill's Site Regions (modified) in Ontario.
Figure 2-1. Hill's Site Regions (modified) in Ontario.

By definition, a landscape approach to Natural Heritage System planning involves assessing the relative ecological value of individual features in a particular area in relation to other similar features in a larger area (i.e. a landscape). Such an approach, particularly when it considers natural heritage features at a variety of scales results in a comprehensive, sound Natural Heritage System. The concept of assessing ecological importance to similar features in a larger landscape can and should be applied even at the site- specific scale. A particular habitat for a species may be considered as significant wildlife habitat because it is under-represented at some scale in the landscape. This could be at the provincial scale, site region or even at the planning area level. Generally, greater priority is given to representation at larger scales.

The concept of representation at a variety of scales in the landscape can assist planning authorities to determine what habitats should be considered significant. For example, the black tern is a colonial nesting bird species that is under-represented (rare) at the provincial scale. Because these colonies are critical to local populations and the species is rare provincially, it is reasonable to assume that all colonies of this species should be considered significant. The great blue heron is also a colonial nesting bird. It is not under- represented (rare) at the provincial scale. Great blue herons can nest in colonies ranging from 5 or 6 nests to well over 100 nests. In smaller landscapes where great blue herons are common, the planning authority may decide that only those colonies with greater than a specific number of nests (e.g. >25), should be considered significant. However, in other small landscapes where great blue heron populations have declined from historical levels and are not common, the planning authority may decide that all colonies that are found in the planning area should be considered significant.

Natural heritage planning at the landscape scale has a number of advantages. These include:

  1. Enabling resource planners to identify the most important natural heritage features based on ecosystem representation and linkages between ecosystems. This is more effectively accomplished when examining the entire landscape and later focusing on the site-specific scale, than starting at the site-specific scale and working up to larger scales.
  2. Allowing planning authorities to reduce their time and costs early in the planning process. The identification of large natural areas and linkages by using ecologically sound, landscape level criteria such as representation, size, shape, distribution, connectivity and community and species diversity (Appendix B) often does not require extensive field studies. Many of the criteria can be applied using existing information on potential sites as well as remote technologies such as satellite imagery and air photo interpretation.
  3. Allowing subsequent finer scale, site-specific planning for significant wildlife habitat to be more focused. After a system of large, well-connected core natural areas has been identified, subsequent efforts to identify site-specific significant wildlife habitat can be concentrated on those portions of the planning area outside of the preliminary Natural Heritage System that have already been identified using landscape criteria.
  4. Providing the best protection for significant wildlife habitats that are difficult to identify and quantify. This would include such habitats as waterfowl breeding habitat, amphibian breeding ponds, snake hibernacula, bat hibernacula, marten and fisher denning habitat, habitats for area-sensitive species and a number of other specialised, highly diverse habitats. These habitats are critical to the survival of many species, but are extremely difficult to locate and, when they are located, the significant portions (i.e. critical habitat) of the habitat are often difficult to quantify. The identification and protection of a system of large, well-connected natural areas with good representation of the ecosystems and natural communities in the planning area will often include many of these features. The large size of these areas can provide better protection than if habitats are individually identified and protected as isolated features on the landscape. Isolated habitats, even with protective buffers, are less effective in protecting the ecological functions of a feature than when that feature is part of a larger natural area.
  5. Providing a greater probability that the habitat size thresholds of some species are met. The habitat size threshold for many area-sensitive species is much larger than the actual territory of an individual breeding pair (Villard et al. 1992). For example, the loggerhead shrike uses open scrubland habitat. The home range for a nesting pair is generally considered to be a radius of approximately 400 metres around the nest (approx. 0.5 km2). However, habitats that appear to be suitable may not be used unless there is a minimum amount of suitable habitat available within a defined landscape. A general guideline is that 10% of the landscape must be suitable habitat. Therefore, within a 100 km2 landscape, 10 km2 would have to be suitable shrike habitat before any of the habitat would be used. The same concept applies to many area-sensitive species. Appendix C lists a number of area-sensitive species and key references for these species.
  6. Allowing better integration of all of the natural heritage features and areas covered by the policy, than when they are identified and evaluated on their own. Ideally, a planning authority’s Natural Heritage System should be comprised of a fully represented system of well-connected natural heritage features and areas broadly distributed across the planning area.

The landscape approach to planning for significant wildlife habitat can be considered a first step in the planning process. It does not eliminate the need for finer scale site-specific identification and evaluation of significant wildlife habitat. Chapters 4 to 7 in this guide provide detailed discussion on the identification of site-specific significant wildlife habitat. Some potentially significant wildlife habitat will be missed when identifying a system of core natural areas at the landscape level. Many of these fine-scale sites can be very important habitats.

Examining significant wildlife habitats at a fine scale after a system of large, well- connected natural areas have been identified at the landscape level, provides the opportunity to gain a better understanding of the ecological functions and species interactions within these areas. This can be very beneficial to a planning authority, particularly during consultation regarding potential development in and adjacent to significant wildlife habitat.

Some field studies may be required to verify existing information or to collect information about potentially significant core natural areas. When conducting field studies, it should be kept in mind that additional information may be required at a later date for site-specific evaluation (Appendix D).

2.1 Gap analysis – A critical tool in landscape analysis

Gap analysis is the most commonly accepted landscape-scale methodology for identifying high priority natural areas in need of protection. Gap analysis is an approach to identifying and fulfilling natural heritage targets. It facilitates the identification of natural features that are not represented or are under-represented within natural areas systems and is the basis of the OMNR’s program for selecting ANSIs. The areas identified form core natural areas around which the rest of the Natural Heritage System can be completed. The key assumptions underlying natural area gap analysis are:

  • that enduring features on the landscape (i.e. landforms) are more stable in their distribution than vegetation or other biotic elements (Noss 1995)
  • that the ecological diversity of an area is largely a result of interactions between climate and enduring features (Noss 1995); and
  • that, by representing all landform-vegetation associations in a protected area system, a significant portion of the biodiversity will be maintained (Crins and Kor 1999)

Collectively, these assumptions recognise that the best way to ensure the survival of the greatest diversity of species is to ensure that the widest possible range of habitat types is protected. OMNR’s current gap analysis procedures are described in Crins and Kor (1999) and are summarised in Appendix E. Other important references include NCASI (1996) and Riley and Mohr (1994).

As described above, a gap analysis is a very useful method for determining which natural areas should be considered for protection. A gap analysis can also be used to determine what natural heritage features may be missing from the landscape. These can also include vegetative or biotic communities that were historically found in the planning area, but are no longer present or have been degraded.