Executive Summary — Ontario Wetland Evaluation System
A summary of the technical guidance documents that use scientific criteria to quantify wetland values and allow comparisons among wetlands.
The OWES is a science-based system that is used to evaluate and rank the relative value of wetlands. The ministry’s OWES manuals are technical guidance documents that use scientific criteria to quantify wetland values and allow comparisons among wetlands. The manuals provide the “evaluation procedures” referred to in the Provincial Policy Statement (PPS) and are used to determine wetland significance under Section 2.1 of the PPS.
The OWES consists of two manuals: the Southern Ontario Wetland Evaluation System (used to evaluate all wetlands located in Ecoregions 6 and 7) and the Northern Ontario Wetland Evaluation System (used to evaluate all wetlands located in Ecoregions 2, 3, 4, and 5). Coastal wetlands, as per the PPS definition, are scored using these OWES manuals. The Ministry of Natural Resources and Forestry (MNRF) periodically reviews and revises the OWES manuals.
The wetland evaluation process involves definition, identification and assessment of wetland functions and values. Wetlands are assessed based on the perceived values of characteristics, activities or expressions of the wetland or its parts that act to maintain ecosystem processes (ecosystem values), or have some utility or amenity value to a segment of society (human utility values). Examples of ecosystem values include primary production, watershed protection, conservation of biological diversity, and maintenance of natural bio-geochemical cycles. Human utility values include flood attenuation, recreation, production of harvestable products, water quality improvements, and research and education.
The wetland functions and values recognized in OWES are grouped into four main categories or components:
Biological: recognizes that wetlands can differ in terms of productivity and habitat diversity.
Social: measures some of the direct human uses of wetlands, including economically valuable products (such as wild rice, commercial fish and furbearers), recreational activities and educational uses.
Hydrological: characterizes water-related values of wetlands, such as the reduction of flood peaks, contributions to groundwater recharge and discharge, and improvements to water quality.
Special features: addresses the geographic rarity of wetlands, ecosystem age, and habitat quality for wildlife, including fish.