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Terrestrial Natural Heritage - About Our Approach

 Using ecological data collected from aerial photography and field investigations, mapping and ongoing monitoring of species and habitat conditions, this approach will provide a powerful tool to direct land use policy, strategic planning and environmental decision-making.


The Terrestrial Natural Heritage approach identifies and evaluates natural heritage systems and assesses the status of habitats and species. Using ecological data collected from aerial photography and field investigations, mapping and ongoing monitoring of species and habitat conditions, this approach will provide a powerful tool to direct land use policy, strategic planning and environmental decision-making.


Complex ecological information is needed for making informed decisions about Terrestrial Natural Heritage. Currently, land-use decisions are made on a site-by-site basis, and fail to consider cumulative impacts. A regional strategy is required to set a context for making ecologically sound decisions. In addition, conservation planning has focused on protecting only the best or most representative natural heritage features. Our approach addresses all of these concerns in order to counteract the degradation of our natural heritage system due to habitat loss, fragmentation and increased urbanization


  • to give clear direction for data collection, land acquisition, ecological restoration and stewardship
  • to provide a systems context and address the cumulative impacts of land use changes in a comprehensive and standardized manner
  • to be efficient, transparent and accessible
  • to raise public, governmental, and agency awareness of our role in making decisions on a shared environment
  • to motivate positive change
  • to educate and engage the public in decision-making
  • to provide a strong basis for setting proactive targets for protection


Our approach organizes aspects of terrestrial natural systems into three categories (or indicators):

  • The Landscape
  • Vegetation Communities
  • Plant and Animal Species

This three-level framework will be used for each of the following components of the approach.

1. Ranking

Assessing the conservation status of the habitat patches, vegetation communities, flora species and fauna species using a quantitative scoring and ranking system.


Every patch of natural habitat in the region is ranked from 1 to 5 according to a series of landscape criteria, including size, shape and surrounding land use (matrix influence). The Total Score for these criteria tells us something about how well a habitat patch may be functioning.

Landscape Criteria:

Size Score | Shape Score | Matrix Score | Total Score

Vegetation Communities

The Ministry of Natural Resources has defined different types of habitats in southern Ontario, according to dominant tree species, the variety of other plants that grow with them and soil and moisture conditions. Our approach applies this Ecological Land Classification system which recognizes many types of vegetation communities ranging from wetlands, meadows, beaches and savannahs. Click here for more information about the Ministry's classification system.

TRCA biologists assign each type of vegetation community a rank, according to its abundance and ecological needs. The map below shows in detail all of the types of vegetation communities that are found in a valley within the TRCA jurisdiction.

Chapman Valley Vegetation Community Types

The types of vegetation communities:

Switchgrass - Beachgrass Open Sand Dune
Switchgrass - Beachgrass Open Sand Dune

Fresh-Moist Sugar Maple Hardwood Deciduous Forest
Fresh-Moist Sugar Maple Hardwood Deciduous Forest


In the past, a species has not been considered a conservation concern unless it is rare. Ironically, protecting a species only when their populations are low results in more species become rare. The Terrestrial Natural Heritage approach uses a more proactive way to monitor species.

Species are all given a rank for their conservation status, according to not just rarity but also their sensitivity to disturbance and their specialized ecological needs. This will be used to address both the goals of preventing rarity and of setting goals for a healthier system.

Maps are developed, showing species of concern that have been observed in the TRCA region. The map below shows that most of the animal species of concern occur in the northern, more rural areas of our region.

Known Distribution of Selected TRCA Fauna

A species of concern: Yellow Spotted Salamander
Yellow Spotted Salamander

2. Data Collection

Collecting information about the habitat patches, vegetation communities and species.
Recent aerial photography is used to collect information at the landscape level. Data concerning vegetation communities is collected in the field by accredited biologists. Species data is gathered by both biologists and by trained volunteers. Also, other life science information is checked and entered into our database. All of this information is used in our ongoing monitoring program (see below).

3. Evaluation

Combining the information to describe the natural heritage system.
Our approach uses the assigned ranks to evaluate terrestrial natural systems at any scale, from the region down to individual sites. The ranks are employed in analysing and reporting under a variety of measures such as the percentage of natural cover in the region or the distribution of species of concern. This analysis is used to evaluate health and to inform the decision-making process (target setting and strategy development).

4. Target Setting

Defining a healthier system.
The TRCA sets measurable targets for attaining a healthier natural system. The Approach incorporates a modelling exercise that uses Geographic Information Systems to evaluate potential conditions at any scale from the region to watersheds, down to individual sites. Both positive and negative changes of various scenarios can be predicted using the modelling. Maps are created to show potential improvements in the landscape by modelling meadows or agricultural lands into forest (or wetland).

5. Strategy Development

Making plans for attaining and sustaining a healthy system.
TRCA's Draft Terrestrial Natural Heritage System (TNHS) Strategy (TRCA, 2004 Draft) proposes an achievable and sustainable vision for the future of the Toronto region's terrestrial natural heritage and describes how we can get there. It uses science-based analytical tools, based on sound ecological criteria, to identify an expanded and targeted land base for inclusion in a terrestrial natural heritage system. The strategy incorporates the most rigorous current thinking on terrestrial natural heritage protection and restoration principles to identify quantity, quality and distribution targets for a terrestrial natural heritage system. In addition, the most comprehensive data on the Toronto region's terrestrial natural heritage assets were used to develop the strategy. Strategic directions for stewardship and securement of the land base, a land use policy framework will help to achieve the target TNHS, and other implementation mechanisms are included in the strategy.

The Draft TNHS Strategy has been completed and has been open for stakeholder comment for much of 2004 and 2005. This consultation process has now been finalized and we are currently reviewing and responding to these comments. Presently, we are rewriting and finalizing the Strategy based on these comments with a final TNHS Strategy anticipated in early 2006.

The Terrestrial Natural Heritage System Strategy is a very important piece of The Living City objectives for Regional Biodiversity and Sustainable Communities.

6. Monitoring and Reporting

Keeping track of the system over time.
The TRCA is developing a Watershed Monitoring Network, which includes terrestrial, aquatic, and water management monitoring protocols. The protocols will measure terrestrial and aquatic health over the long term. The intent of the Network is to bring community and government initiatives together to form a more complete program.

The terrestrial monitoring program will fill the current need for landscape, vegetation communities and species indicators to be comprehensively monitored and reported on at regular intervals.

Monitoring Maps:

Jack-in-the-Pulpit Locations | Michigan Lily Locations | White Oak Locations | Ovenbird Locations |
Northern Spring Peeper Locations | Gray Treefrog Locations | White Trillium Locations

Progress Report

Download The Terrestrial Natural Heritage Program of Living City Progress Report -11,750K pdf icon

Terrestrial Volunteer Monitoring Program Progress Report 2006 -6,425K pdf icon


Size Score:Landscape Criteria Size Score

Shape Score:Landscape Criteria Shape Score

Matrix Score:Landscape Criteria - Matrix Score

Total Score:Landscape Criteria - Total Score

Switchgrass - Beachgrass Open Sand DuneIntact sand dune systems are very rare along the western part of Lake Ontario. The best-developed examples are at Toronto Island and Frenchman's Bay. In the foreground of the picture is a sea-rocket open sand beach, with sand dunes dominated by beach grass (Ammophila breviligulata) centre. In the background are some areas of treed and shrub sand dunes with eastern cottonwood (Populus deltoides) and sandbar willow (Salix exigua)

Beach and dune areas have a unique assemblage of plants and animals. They form in response to natural wind, wave and current action. The Toronto Islands formed as a sand spit from material eroded off the Scarborough Bluffs and carried westwards. Hence they are the same type of feature as other Great Lakes sand spits such as Presqu'ile, Sandbanks, Long Point, Rondeau and Pinery. In spite of extensive modification and extreme urbanization a couple of kilometres to the north over the past two centuries, the Toronto Islands retain portions of very high-quality habitat. These areas have been designated by the province as Areas of Scientific and Natural Interest (ANSI).

Coastal habitats often face threats from shoreline stabilization efforts: the plants there require moving sands. They also are negatively affected by intensive recreational use due to trampling. With the some care, a balance can be found between protection of the dunes and recreational use. The Lake Ontario shoreline in our region, as well as Great Lakes shorelines in the province, are a focal point of our natural heritage system.

Fresh-Moist Sugar Maple Hardwood Deciduous Forest:Deciduous forests dominated by sugar maple are one of our most well-distributed types of natural habitat. On moist sites on clay-based soils such as at the Humber College Arboretum (shown), or along the edges of floodplains, sugar maple can grow with a variety of other hardwoods, including bitternut hickory (Carya cordiformis), white ash (Fraxinus americana), and blue beech (Carpinus caroliniana).

On healthy sites where urban impact is limited, these rich sites host a large array of spring-blooming wildflowers whose activity peaks before the trees come into leaf. Such wildflowers include spring beauty (Claytonia spp.), trillium (Trillium grandiflorum and erectum), trout lily (Erythronium spp.), and squirrel corn (Dicentra canadensis).

Yellow Spotted Salamander:This species is experiencing population declines, presumably throughout its range. Local populations are thought to be decreasing due to habitat loss and fragmentation.

The Spotted Salamander prefers moist deciduous or mixed woodland, particularly where there is available cover in the form of stones, logs or boards. It breeds in woodland ponds and shallow marshes large enough to maintain water through much of the summer, and usually without fish. The Spotted Salamander burrows into the ground during the summer.

Spotted Salamanders should be considered sensitive to fragmentation because they need good connectivity between woodland and wetland habitat. Individuals have been recorded travelling 90 to 180 metres between these habitat types, however, movement outside of migration to breeding pools is restricted.

The Spotted Salamander is known to be sensitive to increases in acidity within breeding pools, which may be a cause for known population declines. It is also sensitive to poor water quality and lowering of water tables due to development. Removal of dead wood results in habitat loss for this species, and trampling compacts soils and destroys ground cover.

Jack-in-the-Pulpit Locations:Jack-in-the-Pulpit Locations

Michigan Lily Locations:Michigan Lily Locations

White Oak Locations:White Oak Locations

Ovenbird Locations:Ovenbird Locations

Northern Spring Peeper Locations:Northern Spring Peeper Locations

Gray Treefrog Locations:Gray Treefrog Locations

White Trillium Locations:White Trillium Locations