UWaterloo study says wetlands provide water filtration services worth billions

A new University of Waterloo study found marshes to be the most valuable wetland type for sediment and phosphorus filtration. The marsh at Point Pelee National Park (pictured) is one of the largest remaining marshes in southern Ontario. Photo Credit: Chris Hill, stock.adobe.com

A new study from the University of Waterloo uses economic valuation to illustrate the importance of water filtration in Southern Ontario’s wetlands, estimating that the process could provide $4.2 billion worth of sediment filtration and phosphorus removal every year.

The value is based on the average rate of sediment accretion in each type of wetland in Southern Ontario, including marshes, bogs, swamps and fens. Researchers calculated how much it would cost Ontario for the removal and disposal of the same amounts of sediment and phosphorus in stormwater management facilities.

Marshes were found to be the most valuable wetland type for sediment and phosphorus filtration, based on the removal rates per hectare, explained  Tariq Aziz, who carried out the study during his PhD and postdoctoral work in Waterloo’s Department of Earth and Environmental Science. Swamps comprise some 87% of Southern Ontario’s wetlands, contributing about 80% of the overall filtration services at a value of about $3.4 billion per year, he said.

“By calculating the economic value of wetland filtration and comparing it to the costs of engineered interventions, we hope to reinforce the importance of protecting our wetlands,” Aziz said in an official announcement from the University of Waterloo.

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Aziz added that wetland protection has only become more critical as sensitive ecosystems continue to be lost by conversion to agriculture or urban development. The research team wanted to show how wetlands are among the most productive terrestrial ecosystems, providing huge economic benefits that could not easily be matched with alternative approaches.

In southern Ontario alone, the study notes that about 68% of wetlands have been converted to other uses since 1980.

Ontario currently accounts for about 25% of all the wetlands in Canada and 6% of all wetlands in the world, according to the Ministry of Natural Resources.

The study, “Economic valuation of suspended sediment and phosphorus filtration services by four different wetland types: A preliminary assessment for southern Ontario, Canada”, was authored by Aziz and his supervisor professor Philippe Van Cappellen. It was published in the journal Hydrological Processes. 

The economic modelling also calculated how much it would cost to replace the existing phosphorus filtration function of wetlands with three different human-engineered solutions. For instance, artificially constructed wetlands could cost an average of $2.9 billion per year; implementing agricultural management practices to remove an equivalent phosphorus load would cost $13 billion annually; and expanding current wastewater treatment capacity to replace wetlands’ filtration service could cost upwards of $164 billion per year.

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