Ecosystem Fragmentation
Ecosystem fragmentation is a serious problem in southern Ontario. It began with extensive forest clearing for agriculture in the 19th century, but has accelerated in the late 20th century with increased pressures from home-building, road construction and other aspects of urban sprawl. A 1999 study of southern Ontario woodlands concluded that “forest fragmentation is more dramatic in Ontario south and east of the Canadian Shield than in any region of comparable size in the Great Lakes Basin.” A 1994 report by the Ministry of Natural Resources on the natural heritage of southern Ontario described the massive transformation of croplands, forests, and wetlands into built environments as “the most significant ecological ‘experiment’ on the landscape.” There is a pressing need for the province to monitor, study and manage the impacts of this ecological experiment.
Fragmentation is the division of a contiguous natural forested landscape into many smaller remnant woodlots. Natural vegetation becomes fragmented into small isolated patches or “islands” with more edge and less forest interior. One comprehensive study in an area between Brantford and Lake Erie found that in 1991 forest cover in the study area had been reduced to 26 per cent of the land surface, in 6,989 patches ranging in size from 0.09 hectares to 3345 hectares. The study found that 75 per cent of the patches were less than 3 hectares, and that fewer than 1 per cent of the patches were larger than 1,000 hectares. The study concluded that 98 per cent of the forest patches had no functional forest interior.
| Forest Fragmentation in Southern Ontario |
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| A study on a portion of the Niagara Escarpment, south of Peel, found that while forest cover increased between 1977 and 1995, the number of smaller forest patches increased, and the amount of forest interior declined by 24 per cent. A 1999 draft state of the environment report by York Region concluded that “forest cover in York Region has decreased from 23 per cent of the total land base in 1977 to 15 to 18 per cent in 1991. The forest that remains suffers from being fragmented into more than 4,000 woodlots. Southern areas of York Region have much less forest cover than the more northerly areas of the region. Cover ranges from 1.5 per cent in Markham to 28.1 per cent in Georgina.” Nine years later, in this rapidly growing region just north of Toronto, there is probably much less. |
Ecological research has shown that diversity of plants and animals is lower in small isolated forest patches, because of the lack of interior sheltered forest cover and invasions into forest cores by predators and non-native plants. Loss of interior habitat and competition from aggressive species bring about decreases in populations of rare and uncommon species, which can lead to extinction. For example, several recent Ontario studies show significant declines in the numbers of migrating and breeding populations of forest-interior bird species, and many studies have found distinct relationships between forest birds and woodland patch and size patterns. Many species of plants and animals are at risk of extinction due to loss of their woodland habitats in southern Ontario. Fragmentation of the landscape also modifies the cycling of nutrients and water, and can radically alter the biological communities in headwater streams that depend on forests for their cooling shade and organic inputs. Fully functioning, intact ecosystems have immense value, not least because they represent the product of millions of years of evolutionary fine-tuning. But it appears that Ontario’s natural heritage is eroding, without the responsible ministries even being able to track the rate of erosion accurately.
Fragmentation is particularly troubling in southern Ontario, not just because of the speed and scale of landscape conversion, but also because the forest ecosystems are unique. For example, deciduous Carolinian forests in southwestern Ontario are very diverse, containing many species of plants and animals at the northern edge of their range found nowhere else in Canada. Unfortunately, these are the most threatened forest ecosystems in Ontario, with forest cover in some counties reduced to as low as 3 per cent.
The Ministry of Natural Resources, which is responsible for biodiversity conservation and protection of the province’s natural heritage, has focused on identifying the best remaining natural heritage sites, with the intention of preserving the most significant sites. To date MNR has not looked at the overall state of the southern Ontario landscape, or assessed changes in forest cover or health. For example, MNR cannot adequately answer the following questions: How much forest have we lost, particularly in the last 20 or 30 years of rapid growth? How much forest do we have left in particular areas? How much do we need for functioning forest ecosystems? Are all forest ecosystem types adequately represented across southern Ontario? How much interior forest and how many connecting corridors do we need for wildlife habitat? How has forest structure or species composition changed?
MNR has very poor data on southern Ontario forests and woodlands. The Forest Resource Inventory (FRI) for southern Ontario is over 20 years old – most of southern Ontario was last inventoried in 1978. In 1997, MNR stated that the FRI was under review for southern Ontario because it did not address the resource management needs of the south. The FRI was designed for large scale classification of forests for timber and other forest industry purposes, but is of little use in southern Ontario where there are fewer and smaller patches of forest, and more complicated planning needs. In 1998, however, MNR staff said they were no longer planning to update the southern Ontario FRI, since all efforts and resources were being put to land use planning and forest industry needs in northern Ontario.
| Loss of Woodlands in Southern Ontario |
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| A 1999 study by the Federation of Ontario Naturalists and MNR’s Natural Heritage Information Centre (NHIC) used historical FRI data to calculate the distribution and losses of total woodlands in southern Ontario. The study concluded that by 1978, more than 80 per cent of woodlands had been lost across southern Ontario, and that only about 30 per cent of the remaining woodland area could be considered original woodland rather than replacement woodland.
In other words, only about 5 per cent of original, pre-settlement woodlands remain, and almost all of the original area has been disturbed, cut-over and altered. The study could not measure trends since 1978, due to the lack of data coverage for most of southern Ontario. |
There are some tools in the Planning Act (PA) and Provincial Policy Statement (PPS) of 1996 that could be used to address ecosystem fragmentation. Under the PA, municipalities must have regard to matters of provincial interest, such as “the protection of ecological systems, including natural areas, features and functions.” Municipalities must also have regard to the Natural Heritage policies of the PPS that state that natural heritage features, including significant woodlands south and east of the Canadian Shield, will be protected from incompatible development, and that the diversity of natural features in an area, and the natural connections between them, should be maintained and improved, if possible. MNR’s Natural Heritage Reference Manual, which provides guidance to municipalities in applying these policies, is discussed on pages 68-69 of this report. ECO is concerned, however, that the tools in place do not appear to be working to prevent ecosystem fragmentation.
Ecosystem fragmentation is a measurable phenomenon, given adequate resources, and MNR has the responsibility and capability to measure ecosystem fragmentation. In 1998 the NHIC proposed a multi-year data maintenance and analysis project covering southern Ontario, “in recognition of the need to have current, high-quality information to conduct informed land use planning and conservation planning in Canada’s most heavily populated and heavily developed region.” Unfortunately, adequate funding could not be obtained from MNR or other partners, and only a few small projects were under taken.
Some fragmentation mapping has now been carried out in southern Ontario, but only in a few selected areas where the information is urgently needed. A 1999 study funded by several agencies used MNR data and geographic information systems technology to map essential core natural areas, existing corridors and potentially restorable links between the cores near Point Pelee National Park, one of Canada’s most endangered ecosystems. Similar mapping was done by MNR in 1999 and 2000 for the Oak Ridges Moraine area, which identified areas of provincial natural heritage interest, including significant woodlands, regenerating areas and connecting lands, to ensure ecological function.
Of utmost importance in dealing with ecosystem fragmentation is the immediate need for detailed and well-funded research. The scale of the problem needs to be better defined. The research must occur under the direction of MNR and the Ministries of the Environment and Municipal Affairs and Housing, the provincial ministries responsible for land use planning and natural heritage, because most municipalities do not have adequate capacity to carry out sophisticated ecological inventory and planning, and cannot address ecosystem concerns that transcend their boundaries. Once the scope of the problem is defined, ministries will be able to evaluate and select management options to slow down or even reverse the damage caused by ecosystem fragmentation. With enough time and commitment, restoration of ecosystems is possible. However, in the short term the responsible ministries must show leadership, because this issue too often is caught in jurisdictional ping pong. Ministries must assist municipalities to ensure that ecosystem fragmentation is adequately considered in land use planning decisions and that provincial interests in protecting natural heritage and functioning woodland ecosystems are safeguarded.
| Recommendation 20:
The ECO recommends that MNR, MMAH and MOE research the scope of ecosystem fragmentation in Ontario and evaluate and select management options to slow down or even reverse the trend. |
| Recommendation 21:
The ECO recommends that the ministries assist municipalities to ensure that ecosystem fragmentation is adequately considered in land use planning decisions and that provincial interests in protecting natural heritage and functioning forest ecosystems are safeguarded. |
| This is an article from the 1999/2000 Annual Report to the Legislature from the Environmental Commissioner of Ontario. |
Citing This Article
Environmental Commissioner of Ontario. 2000. "Ecosystem Fragmentation." Changing Perspectives, ECO Annual Report, 1999-2000. Toronto, ON : Environmental Commissioner of Ontario. 135-139.
