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The Great Lakes basin and the land surrounding it support a wide variety of Canada’s wildlife species, including many of Canada’s species that are endangered, threatened or of special concern. The density of human population, habitat loss and degradation, and growing pollution has put a great deal of stress on basin ecosystems.
The best way to preserve biodiversity is to protect the existing habitats which already support wildlife populations. But doing the right thing to conserve wildlife species and their habitats can be a difficult task: the habitat requirements vary for each of those species and ecological interactions are complex.
How Much Habitat is Enough is a project of Environment Canada’s Canadian Wildlife Service which strives to provide science-based answers to where, how much, and what type of wildlife habitat is needed in critical areas – focussing on the Great Lakes region. The initiative provides guidance for land-use planning and helps to fill a conservation biology knowledge gap. The latest effort is a report on the viability of urban forests as bird habitat.
The first edition of How Much Habitat is Enough: A Framework for Guiding Habitat Rehabilitation in Great Lakes Areas of Concern, published in 1998. It contained 18 guidelines on selecting where wetland, riparian (i.e. riverside) and forest habitat could be restored most efficiently to support wildlife populations. These include minimum per cent forest cover (30 per cent), maximum area of a watershed that should be impervious (10 per cent) and ideal wetland watershed cover (10 per cent). The guidelines were general and meant to be adapted to local conditions in the Great Lakes basin.
Parts of the Great Lakes basin are designated as Areas of Concern due to contaminated water, degraded habitat, and impaired wildlife populations. Severn Sound was an Area of Concern until 2002. How Much Habitat is Enough guidelines were used in its restoration. Thousands of trees were planted, phosphorus levels in water dropped, and some fish species reappeared. In total, 416 hectares of land and 138 kilometres of stream were protected.
How Much Habitat is Enough has seen widespread use as a tool to guide Areas of Concern restoration projects and planning. Used in over 40 natural heritage and watershed strategies, it has become a conservation biology primer and guide outside of original target Areas of Concern. This recently led to a second edition that captures the newest science on the topic.
As part of the How Much Habitat is Enough initiative Environment Canada is now releasing another report, Area Sensitive Forest Birds in Urban Areas, this one looking at urban woodlands as habitat for forest birds.
Previously, forest breeding bird surveys were conducted by staff of the Canadian Wildlife Service in the Great Lakes region to assess the guidelines related to forest bird habitats. The results showed that only large forests could support a rich variety of forest-interior birds and that many of the smaller forest patches currently available were not enough to support the species normally expected in that region. New science shows that in addition to forest size, the percentage of forest in an area is a major factor in determining what forest birds will breed in an area. These findings raise questions about forest birds, especially area-sensitive forest birds, living in urban areas.
The new report finds only 13 of over 40 species of forest breeding birds that potentially existed in Toronto still exist in its urban forests. The report recognizes that urban forests are ecologically beneficial in general, but their restoration is unlikely to increase the number of area-sensitive forest breeding bird species.
Therefore, birds that require forest interiors to successfully reproduce will be best provided for by ensuring that remaining non-urbanized parts of watersheds have a minimum 30 per cent forest cover.
How Much Habitat is Enough has guided watershed-scale conservation efforts through its adaptation and adoption in multiple natural Heritage and Watershed Strategies across Southern Ontario. In settled landscapes, municipal planning is the critical factor in how land is used. Natural heritage and watershed strategies influence municipal planning and now How Much Habitat is Enough guidelines are also being considered directly by planners. This guidance will be key in landscapes such as the Carolinian Life Zone, that part of Canada in south-west Ontario that has a relatively milder climate and a rich diversity of species.
The Carolinian zone is also home to more than 40 per cent of species present on the national list of endangered species. Initiatives such as the Essex County Biodiversity Strategy have adapted the guidelines to be compatible with the local landscape. Such projects will help to provide for habitat restoration and conservation.
The success of How Much Habitat is Enough indicates a clear need for conservation biology science to get to decision makers. Respondents to a 2002 assessment confirmed a wish for more science-based guidance, but revealed many principles that are taken for granted in the natural sciences are not often well known to elected officials, planners or even restoration practitioners. For the future, the continued challenge will be for scientists to provide clear information to already overloaded conservation volunteers, and professionals.