Across North America, widespread wetland drainage has taken place over the past two centuries, mostly for agricultural conversion. Ashbridge’s Marsh was an extensive freshwater wetland at Waasayishkodenayosh, the mouth of Toronto’s Don River. Large-scale disturbance began during the early European settlement era, eventually resulting in almost complete wetland drainage and the emplacement of many meters of fill by 1900. In 2021, during river channel and wetland restoration, buried wetland soils were uncovered. Here, we present analyses of geochemical properties of these buried soils along with radiocarbon ages, pollen assemblages, and Indigenous knowledge of the pollen taxa recorded to better understand the pre- or early settlement era Ashbridge’s Marsh. Radiocarbon dates on seeds returned ages spanning the 19th century, with one seed dating to the 16th century. Bulk density, carbon and nitrogen analyses are consistent with freshwater marsh habitat. Pollen diversity was high, with ∼35 taxa recorded per sample. Marsh and swamp taxa co-dominate the assemblages, including two endangered and one extirpated tree species; abundances of disturbance indicators including ragweeds ( Ambrosia L.) were low. Taken together, the data indicate that these buried soils represent relatively undisturbed ecosystems and can therefore be used alongside Indigenous knowledge to inform wetland restoration.
Sengupta et al. (Thu,) studied this question.