Scoring and Ranking System

Native birds, amphibians, reptiles, mammals, plants, and vegetation communities are assigned local ranks based on ecological data collected by Toronto and Region Conservation Authority (TRCA) and other agencies.

Scoring and Ranking: A Proactive Approach

Based on NatureServe’s Natural Heritage Methodology, TRCA has developed its own scoring and ranking system for all species and vegetation communities found in the Toronto region.

This system was developed in the late 1990s out of growing concern for common species disappearing as land use development expanded northward. This proactive approach is designed to alert conservation managers to potential local species declines and losses in the future.

Currently, 58% of species in TRCA’s jurisdiction are listed Regional Species of Conservation Concern.


This listing of Species of Conservation Concern has proven to be an important and effective tool in making land-use and management decisions at the local, watershed and regional scale. This knowledge supports:

  • Predictive computer modeling
  • Natural heritage system targets
  • Land management decisions
  • Municipal planning
  • Watershed plans and report cards
  • Development applications

TRCA ecosystem science field staff team member collects data on local vegetation communities


All species (flora and fauna) and vegetation communities are assigned an L-rank from L1 to L5 based on their distribution throughout the jurisdiction. The ranks indicate the degree to which various species/communities need protection:

  • L1 to L3 = Regional Species of Conservation Concern
  • L4 = Urban Species of Conservation Concern
  • L5 = Not of Conservation Concern currently

View Methodologies:


The score detail informs the conservation actions needed to enhance the prospects for success. The following criteria are used to score species and communities:

Vegetation Communities

  • Local Occurrence
  • Geophysical Requirements (hydrology, soil type, pH etc.)

Vegetation Community Ranks and Scores – 2023

Flora Species

  • Local Occurrence
  • Population Trend
  • Habitat Dependence
  • Sensitivity to Development (collection or removal, outcompeted by invasive species, etc.)

Flora Species Ranks and Scores – 2023

Fauna Species

  • Local Occurrence
  • Population Trends (Regional and Continental)
  • Habitat Dependence
  • Sensitivity to Development
  • Area Sensitivity
  • Patch Isolation Sensitivity

Fauna Species Ranks and Scores – 2023

PLEASE NOTE: Native species and communities thought to be locally extinct (LX rank) and non-native species and communities (L+ rank) are only ranked and not scored.

Contact Us

Questions? For more information, please contact:
TRCA Watershed Planning and Ecosystem Science |