Economic model shows southern Ontario wetlands provide $4.2 billion in natural filtration

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WATERLOO — An economic model has found that Ontario’s wetlands provide $4.2 billion in natural filtration to keep drinking water clean.

“People don’t care so much about these wetlands, they think they’re wasteland and we can convert them into shopping malls,” said Tariq Aziz, a postdoctoral fellow in the Department of Earth Sciences and of the environment from the University of Waterloo.

“But they provide us with a multitude of ecosystem services that are really essential to our well-being.”

The wetland ecosystem filters sediment and removes phosphorus from the water before feeding nearby waterways.

Aziz and supervising professor Philippe Van Cappellen compared natural filtration with Ontario’s cost to clean water through stormwater management facilities, in the study published in the journal Hydrological Processes.

By assigning a monetary value to wetlands, Van Cappellen said they were trying to show the importance of wetlands.

The entire wetland ecosystem, which includes animals, vegetation and the slower flow of water compared to streams, contributes to its natural filtering abilities, he said.

Wetlands can be divided into marshes, bogs, swamps and fens.

Swamps are dominated by trees or shrubs. Swamps usually have areas of open water with floating plants like water lilies, bogs are areas covered in nutrient-poor, highly acidic peat and fens are often found on peat, but are less acidic and have more than the bogs.

While Aziz found swamps to be the most valuable based on sediment and phosphorus removal per hectare, swamps contribute to water filtration at a higher rate as they make up 87% of wetlands from southern Ontario.

Aziz and Van Cappellen compared natural filters to three man-made alternatives: building an artificial wetland, which would cost $2.9 billion a year. Another solution implementing agricultural best management practices to remove phosphorus that would cost $13 billion per year, or expanding wastewater treatment capacity costs $164 billion per year.

Most of Waterloo Region’s drinking water comes from groundwater, but Van Cappellen said places like Brantford that draw directly from the Grand River are being impacted by lost wetlands.

“Sometimes to really put things into perspective, it’s good to put a monetary figure,” Van Cappellen said.

“It basically allowed (Aziz) to help the debate about the efforts we are making to protect our wetlands,” Van Cappellen said.

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