TRCA's Updated Regional Target Natural Heritage System 2022

Includes key regional natural heritage features and areas important for the health and resilience of aquatic and terrestrial ecosystems.

What is TRCA's updated regional target NHS?

In 2022, building on the principles the  Terrestrial Natural Heritage System Strategy (2007) , TRCA completed an update to the technical component of the Strategy. Using updated data and an integrated approach,  TRCA's updated regional target NHS (2022)  identifies key natural heritage features and areas that are important for terrestrial and aquatic ecosystem across the landscape. The updated NHS was approved as a science-based screening tool by TRCA's Board in October 2022.

TRCA's updated regional target NHS:

  • Builds on the systems approach of the TNHSS (2007) and ensures the regional target NHS remains current and relevant to achieve TRCA and its municipal partners’ natural heritage objectives as land use and climate continue to change.
  • Identifies the most strategic areas for the NHS that should be targeted for protection, restoration, and enhancements to improve terrestrial and aquatic ecosystem health and resilience within and across watershed boundaries based on the most up-to-date science and data.
  • Provides an integrated and comprehensive decision support tool, as well as a series of stand-alone datasets, that helps to characterize terrestrial, aquatic, and hydrological priorities within and across the watersheds. This can inform various TRCA and municipal initiatives for ecosystem management and climate adaptation.

TRCA’s updated regional target NHS identifies 35% of the TRCA’s jurisdiction as target NHS comprising of existing natural cover (23.3%) and potential natural areas (11.9%). An additional 16.5% of the jurisdiction is identified as the Contributing Areas that support the NHS features and functions, but where traditional restoration opportunities may be limited due to its existing conditions (e.g., built areas) and/or future plans (e.g., approved for future development). The Contributing Areas are mostly within the urban land uses that have been identified as important for various ecological functions.


2022 Natural Heritage System

View the interactive map to explore the updated NHS in the Toronto region.

NHS 2022 Dashboard


How was TRCA's updated regional target NHS identified?

A total of 37 datasets, both existing and new, that characterizes ecosystem features, functions , and priorities were used in the model that was used to delineate the target NHS (2022).

Scroll down to view the series of data layers, classified into four major groups, used in the process.

1. Locked-in Features and Areas

This group includes 9 available datasets on natural features and areas that should be included by default within the NHS as they represent mostly existing features. In an urban landscape such as ours, these are the last remaining areas that contribute to overall ecosystem health:

  • Areas of Natural and Scientific Interest (ANSI): These are protected natural landscapes or features that have been identified as important for life science or earth science values.
  • Fish habitat: TRCA's regulated watercourse layer with a 10 m riparian buffer.
  • Habitat of endangered and threatened species: Includes all of the locked-in features and areas criteria listed here.
  • TRCA conservation lands: Includes all protected valley and stream corridors, flood plains, Lake Ontario shoreline and Environmentally Significant Areas (ESAs) within TRCA lands.
  • Wildlife habitat: Includes ESAs and all natural cover within 5 km from the shoreline (migratory bird habitat).
  • Wetlands: Identified using natural cover orthophotos, and includes Ecological Land Classification vegetation communities, Provincially Significant Wetlands (PSWs) and restored wetlands.
  • Woodlands: All forest and successional forest natural cover (derived from orthophotos) and restored woodlands.
  • Valleylands: Represented by the crest of slope, which is within regulation mapping as part of TRCA's regulated area.

2. Aquatic Functions

This group includes 6 datasets that identify the priority areas for aquatic species and habitat, including the upland areas that are important contributing areas for sensitive in-stream habitat and are as important for hydrological linkages:

  • Fish habitat suitability guilds: Habitat suitability analysis was done to identify four functional trait groups for fish communities. The habitat needs of these fish communities provide insight into the thresholds needed for conservation and restoration of natural cover. 
  • Riparian natural cover: All natural cover and forest cover as riparian cover for reach contributing areas.
  • Ecologically Significant Groundwater Recharge Areas: These include ecologically significant areas for replenishing groundwater systems.

3. Terrestrial Functions

This group includes 21 data layers that identify priority areas for terrestrial species and habitat, including areas predicted to have high suitability for multiple groups of species, connectivity priority areas, and areas with high diversity and/or combination of species and vegetation communities, including:

  • Biodiversity hotspots: Determining where differences in biodiversity are found across the Toronto region helps identify sites that are unique (biodiversity hotspots) relative to other sites in the jurisdiction.
  • Habitat connectivity: Habitat connectivity analysis and models were generated to identify regional priority wildlife corridor, and to assess if these corridors can address the habitat needs of multiple species.
  • Habitat suitability for birds and amphibians: Habitat Suitability Analysis was completed for nine groups of bird and amphibian species. These groups help to identify key areas that support biodiversity through functioning habitat.
  • Remaining natural cover: All natural cover not included in locked-in features and areas.

4. Municipal Natural Heritage System

This includes 1 consolidated data layer reflecting the areas that were identified as NHS priorities in municipal official plans (as of when the analysis was completed in 2020). This data layer plays a critical role in the identification and protection of natural features and areas.

The locked-in natural features and areas were included by default in the target NHS as they represent mostly existing features. The other data layers were used to select additional areas, mostly for restoration and enhancements, using an optimization tool called Marxan (Ball et al. 2009). It integrates and evaluates multiple criteria to identify the most optimal areas that can maximize the highest priority areas for each criteria.

In this analysis the model was set to select the top 40% priority at the watershed scale and 50% priority at the regional scale. This allowed for identification of the priorities at both watershed and regional scale. These additional areas were merged with the locked-in areas to identify TRCA’s regional target NHS and classified into existing natural cover, potential natural cover, and contributing areas based on land use and land cover information.


What does TRCA's updated target NHS mean?

Provincial directions require municipalities to identify and provide adequate protection and enhancements to the natural heritage system.

TRCA’s updated regional target NHS is a science-based screening tool that highlights the existing and potential features and areas that are important for long term health and resilience of ecosystems in TRCA’s jurisdiction.

It is intended to inform TRCA and its municipal partners various strategic and site level initiatives (with appropriate refinements), including:

  • watershed and subwatershed planning,
  • land use and infrastructure planning processes,
  • land securement and management,
  • ecological restoration and management,
  • green infrastructure implementation,
  • municipal comprehensive reviews, and
  • official plan review processes.

TRCA’s updated regional target NHS is not intended to disrupt existing decision-making processes, but rather to inform them based on up-to-date science and to identify partnership opportunities to facilitate collaborative conservation initiatives.


Explore more information about the Natural Heritage System in TRCA's Watershed and Ecosystems Reporting Hub:

Environmental Conditions of the Toronto Region