Ontario’s Greenbelt is composed of nearly 2 million acres of protected land including natural areas that provide ecosystem services to millions of people. While these areas face reduced pressure from land use conversion, they still face a pressures typical of natural systems in peri-urban landscapes including loss of biodiversity, invasive species, impacts from infrastructure projects and a changing climate. In order to determine the extent to which these pressures are shifting natural systems, indicators of system health are needed. This report will use existing natural system spatial data to quantify changes in the natural system across the Greenbelt. Through municipal case studies relying on previously collected high-resolution spatial and field-collected information, a list of recommended indicators will be developed, identifying high priority indicators for collection and reporting. It will also provide recommendations for additional, precise monitoring criteria based on data analysed at both regional and local levels.