We recently investigated if it would be possible to put together a greenhouse inventory for the Greenbelt. Our report is unique in that it considers land-use emissions from agricultural practices and natural systems alongside traditional emission sectors. While there were some high level estimates and gaps in our analysis, our best net emissions estimate for the Greenbelt is about 4.35 MtCO2e / year, or 2.5% of Ontario's total. In contrast, the Greenbelt's natural assets store 261 MtCO2e. This significant difference between what the Greenbelt stores and what is emitted emphasizes the critical need to protect carbon sinks, such as farmland and forests as they play an important role in combating climate change.
The full report is available here.