Biodiversity in Ontario's Greenbelt (PDF) - David Suzuki Foundation

In 2010, the conversion of agricultural lands to urban, built-up areas was also found to be a
significant threat to species at risk that may rely on agricultural fields for surrogate habitat, such
as grassland species. 63 Agricultural lands provide food and other commodities to southern Ontario
residents — but they can also act as habitat for many species at risk, such as the American badger
and barn owl. From 1993 to 2007, 68 per cent of the roughly five per cent of land that had been
converted in the Greenbelt was agricultural. 64 York Region underwent the most significant land
conversion of all the regional municipalities in the Greenbelt, accounting for 32 per cent of the land
converted in the Greenbelt between 1993 and 2007. 65
Edge effect
Agricultural lands
provide food and other
commodities to southern
Ontario residents — but
they can also act as habitat
for many species at risk,
such as the American
badger and barn owl.
Many species at risk in the Greenbelt require relatively undisturbed natural areas of a significant size
for all or some of their life cycles. As areas decrease in size because of habitat loss or fragmentation,
the “interior” habitat they offer grows smaller and the amount of exposed “edge” habitat grows larger,
augmenting threats to species that require the safety of interior habitat conditions for breeding
and/or nesting.
In woodlands, edge habitat is usually warmer, drier and more susceptible to disturbance by
predators and parasitic or invasive species than the sheltered, wetter interior forest. The Natural
Heritage Reference Manual defines interior habitat for woodlands as more than 100 metres from the
edge of the forested area, meaning that woodlands must be of a significant size
to ensure this habitat exists. 66 The smaller the forest patches become, the fewer
species remain within them. 67 In woodlands less than 100 hectares in size, for
example, interior habitats are smaller than what is required by species like the
hooded warbler and Acadian flycatcher. 68 The Greenbelt currently has an average
of 30 per cent natural cover (forests and associated wetlands), with areas in
the Niagara Escarpment containing well over 40 per cent. 69 These areas stand
in marked contrast to some sections of southwestern Ontario, where natural
cover can be as low as five per cent of the land base. 70 Environment Canada
recommends that watersheds retain a minimum of 30 per cent natural cover
to retain critical interior forest habitat. 71
63 Ryan Cheng and Peter Lee. 2008. Urban Sprawl and Other Major Land Use Conversions in Ontario’s Greenbelt
from 1993-2007: A Change Analysis Project Using Satellite Imagery. Report to the David Suzuki Foundation.
Global Forest Watch Canada. Edmonton, Canada. pp.4–5.
64 Cheng and Lee, Urban Sprawl, p.6.
65 Cheng and Lee, Urban Sprawl.
66 Natural Heritage Reference Manual, p.198.
67 Environment Canada. 2004. How Much Habitat Is Enough A Framework for Guiding Habitat Rehabilitation
in Great Lakes Areas of Concern. (2nd ed.). Report for the Ministry of the Environment. p.7.
68 Landowner Resource Centre. Conserving the Forest Interior: A Threatened Wildlife Habitat. www.lrconline.
com/Extension_Notes_English/pdf/forInterior.pdf.
69 Wilson, Ontario’s Health, Canada’s Future, p. 24.
70 Ontario Nature. 2004. Suggested Conservation Guidelines for the Identification of Significant Woodlands in
Southern Ontario. Report for Ontario Nature. Toronto, Canada. p.74.
71 Ontario Nature, Suggested Conservation Guidelines, p.8
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Biodiversity in Ontario’s greenbelt