What important ecological trends influence greenlands protection?

The previous sections of this paper have discussed some of the recent trends in development patterns and Natural Heritage planning that relate to the loss or protection of greenlands in the Central Ontario Zone. However, of perhaps equal importance are several significant scientific advances that have recently been made in the burgeoning field of landscape ecology. In the past decade we have witnessed the emergence of a number of trends that are strongly influencing the identification of greenlands as well as the policies designed to protect these features. Perhaps foremost among these is the concept of landscape connectivity: the belief that one of the keys to a healthy system of greenlands is the maintenance of physical habitat connectors between and among large natural core areas such as major forests, wetlands, and valleys. Connectivity has been championed by a number of influential members of the scientific community and has recently been the focus of a major research project of the Federation of Ontario Naturalists (FON) and the Nature Conservancy of Canada (NCC) known as "The Big Picture Project." Using sophisticated computer modelling, a conceptual model of landscape connectivity for Ontario south of North Bay has been developed, based on a series of several kilometre-wide connectors that criss-cross the south-central portion of the Province, linking large core areas.

The concept of connectivity is also one of the cornerstones of the recently released Oak Ridges Moraine Conservation Plan. The plan is intended to establish habitat connections between key natural heritage features at a more local level than the FON model, but based on the same fundamental principle that everything needs to be linked together so as to facilitate the movement of plants and animals (and in doing so promote the exchange of genetic material) over large portions of the landscape.

There are two opposing schools of thought among ecologists regarding the merits of landscape connectivity and corridors. The prevailing argument is that corridors help offset the instability caused by habitat fragmentation. The concept of connectivity has its detractors, however, who believe that corridors provide conduits for disease, predators, and exotic species to spread through a population. Analyzing the pros and cons of this debate are beyond the scope of this paper. On balance, the merits of corridors, especially between core natural areas, outweigh their detrimental aspects, but they should not be viewed as a "cure-all" to counter the ills of habitat fragmentation.

It is important to remember that the purpose of establishing and maintaining landscape connectivity is to support the core greenland units. Core areas are the anchors of the natural heritage system and should be afforded greater consideration than corridors. Research into the dynamics of wildlife communities inhabiting some of these larger forest patches is revealing a disturbing trend. Rather than being population "sources," many of these forests may instead be acting as "sinks," exhibiting surprisingly poor productivity given their relatively large size. On an ecological basis, there is a tendency to overestimate the value of these forest patches as habitat. Ecologists are gradually discovering that some of the animal species one would expect to find in large forest patches are in fact absent, or present in small numbers and non-productive.

One of the practical disadvantages associated with re-connecting the landscape is that it can be extremely expensive to construct, even when some of the links in the chain (such as small woodland patches between larger forest blocks) are already in place. With limited financial resources available, it is questionable whether investments of this magnitude will achieve the best return. In the view of some, habitat restoration to close gaps and smooth out the edges of large core areas would be more cost-effective and ecologically sustainable. A recent analysis of the state of forest cover in the former Region of Hamilton-Wentworth (now the City of Hamilton) demonstrated that restoring a one-hectare forest gap could, in some situations, result in the creation of up to six hectares of forest interior habitat. Biodiversity cannot be maintained at current levels or expected to return to former levels without the existence of large, contiguous patches of natural habitat. In many cases this will require a commitment to undertaking habitat restoration (that is, creating more habitat), rather than merely maintaining the existing level of available habitat.