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Terrestrial Natural Heritage

The Living City depends on a network of natural habitats to maintain biodiversity and a healthy environment for the benefit of all living things. Toronto and Region Conservation is working to identify and build this critical network of natural areas through its innovative Terrestrial Natural Heritage Program.

Based on an extensive inventory of our regions forests and wetlands, animals and plants, the program will provide information on the health of our region and monitor changes. It will show the linkages between terrestrial natural systems and aquatic habitats, water management, air quality, loss of species, recreation, safety and aesthetics. It will identify the ideal network of natural areas needed for a healthy functioning ecosystem and set priorities for protection and restoration. Most importantly, it will provide a science-based tool that will help inform planning and development decisions that protect important natural features and functions.

What is Terrestrial Natural Heritage?

Terrestrial Natural Heritage includes plants, animals and natural communities associated with the land, as opposed to aquatic environments. It encompasses wetlands and plants and animals that require land for at least part of their life cycle (such as amphibians and waterfowl).

Terrestrial Natural Heritage includes: Water, Land, Air and forest

Water Land Air Forest

Our Natural Heritage System

A Natural Heritage System consists of all of the natural cover in a region. It is called a "system" because of the interactions and dependencies between and among its parts.

According to the Great Lakes Remedial Action Plan, the recommended amount of natural cover needed for reasonably healthy and resilient ecosystems is 30 per cent. Currently, natural cover in the TRCA region stands at approximately 17 per cent and falls as low as 5 per cent in some municipalities.

In the more rural areas of the jurisdiction, such as the Oak Ridges Moraine in the north and the Duffins Watershed and Rouge Valley in the east, more sizable areas of natural habitat remain with some remarkable natural heritage features. Rouge Park, for example, possesses a high diversity of plant and animal species and is a vital ecological link between Lake Ontario and inland areas. As well, Tommy Thompson Park on the waterfront is an important haven for migrating birds.

Habitat Map Large
Forests, Meadows, Wetland in TRCA Region


Habitat fragmentation, particularly forest fragmentation, is a major concern for terrestrial habitat within the TRCA's jurisdiction.

Jack Inthe PulpitPlant and animal populations are seriously affected by fragmentation. For example, animals that require cover for movement are unable to cross open agricultural areas between forest patches due to the risk of predation. Other barriers such as roads and urban areas are formidable or dangerous obstacles to animal movement.

NewtHabitat fragments - especially forests - have edges on all sides. The issue of negative "edge effects" is of particular concern for biodiversity in fragmented forest landscapes. These negative effects include: increased wind damage and drying, growing populations of non-native species which crowd out other plants, and increased predation of birds and other small animals by such species as raccoons, skunks, foxes, crows, etc.

FragmentationHabitat fragments are also more vulnerable to disturbance by humans. Recreational pressures can lead to trampling, erosion, and the accidental introduction of invasive exotic plants. Wildflowers are often picked or removed to be transplanted in people's gardens. Amphibians and reptiles are collected by children, and house cats hunt for birds and small mammals. Dumping of refuse in natural areas remains a common practice, while pesticides, pollutants, and dust can drift in to habitat patches and affect sensitive species. Even noise from backyards, industry, or construction can disrupt the activities of some species.

Biodiversity in Our System

The TRCA has identified more than 200 flora and fauna "species of concern" that are at risk in the region due to habitat loss or sensitivity to urbanization. Sensitive species that are indicators of good health in our environment, such as spring peepers and scarlet tanagers, have been extirpated (extinct locally) from the southern urbanized portion of the region. Helping to conserve and enhance biodiversity in the region will ensure that there will be opportunities for us and our children to experience the richness and variety of life which has evolved over millions of years.

Peepers Large
Map of Location of Spring Peeper and Scarlet Tanager

Terrestrial Natural Heritage System Strategy (TNHSS)

The Strategy -2,014K pdf icon

Appendix A -1,598K pdf icon

Appendix B -1,638K pdf icon

Appendix C -1,664K pdf icon

Appendix D -2,348K pdf icon

Appendix E -3,940K pdf icon

Appendix F -1,062K pdf icon

Appendix G -1,062K pdf icon

Appendix H -1,026K pdf icon

Appendix I -1,397K pdf icon

Appendix J -1,031K pdf icon

Terrestrial Volunteer Monitoring Program

Monitoring Results 2002-2007 - 2,223K pdf icon