State of the Wetlands in the Lake Simcoe Watershed Ontario Streams Technical Report No
July 2018 State of the Wetlands in the Lake Simcoe Watershed Ontario Streams Technical Report No. 2018-01 Alexander Kissel, Habitat Technician & Alice Choi, GIS Technician, Ontario Streams ontariostreams.ca Summary Wetlands in the Lake Simcoe Watershed are critical to the health of the Lake and its surrounding ecosystem. They cover 18.4% of the surface area around the Lake or 52 847 hectares (ha). About 62.4% of these wetlands have been evaluated using the Ontario Wetland Evaluation System (OWES) Southern Manual. The distribution of wetlands vary with fewer and smaller wetlands on the Oak Ridges Moraine (7.1% of surface area), the Schomberg Clay Plains (5.5%) and the uplands west of the the Lake (10.9 to 12.7%), contrasting with the larger valley and shoreline wetlands in the lowlands around the Lake (25.7%). Small wetlands play an important role particularly in the landscapes where they make up a large portion of the wetlands. A high resolution (15 centimetre pixel) analysis of aerial imagery from 1999/2002 to 2013/2016 for the Lake Simcoe Watershed has shown that many small wetland losses, and the occasional larger ones, add up over this time period to a loss of almost eight square kilometres or 773 ha (1.5% of the total wetland area). This loss is higher than previous estimates using lower resolution (30-metre pixel) satellite imagery which cannot pick out the smaller losses that have a large cumulative impact. The highest losses have been from agriculture (46.4% of all losses), following in descending order by residential (10.5%), peat extraction (10.4%), canals (9.6%), highways/roads (6.6%), industrial/commercial (5.7%), fill (4.6%), dug-out ponds (4.3%), recreation (1.6%) and aggregates (0.3%).
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