Relying on stormwater management (SWM) ponds to restore the depleting wetlands is not sustainable and lacks the critical ecosystem services vital for biodiversity, a new study found.
With the continued losses of wetlands projected in the near future and emphasis on the underestimation of provincial wetland loss, the study captures the contributions of SWM ponds in a changing network of water bodies and the effects of land use and land cover in this change.
Waterloo researchers examined wetland loss, SWM pond creation and land use-based trends in seven southern Ontario municipalities within the most populated ecozones in Canada from 2002 to 2010 using a geographic information system.
Rebecca Rooney, an associate professor in the Department of Biology and lead of the Waterloo Wetland Lab, has been studying the ecological functions of stormwater ponds in comparison with natural wetlands since 2015.
“When wetlands are destroyed, the water they used to hold still needs to go somewhere. We build stormwater ponds to keep it from flooding basements and damaging property, but wetlands are so much more than basins that hold water. Ecosystem services like carbon storage, biodiversity support, and water filtration that natural wetlands provide for us for free are not necessarily replaced by stormwater ponds,” said Rooney.
She and her biology graduate students are continuing to investigate the trade-offs that come from this wetland to stormwater management pond exchange and aim to improve the design of new ponds to help preserve wetland ecosystem services in urban areas.
For the years under study, the findings show that the total number of created SWM ponds was 1.6 times greater than the number of wetlands lost for all municipalities combined and that an overall rate of 0.13 per cent of wetland area was lost per year.
“This is concerning because of the low proportion of wetlands left in these areas and the fact that the average SWM pond was smaller than the average lost wetland, which poses a big environmental challenge,” Birch said.
The researchers argue that wetland losses will continue with trends towards their replacement by SWM ponds. They observed that losses are concentrated among wetlands that are generally not protected by provincial policies because of their small size.
“We recommend that protections be strengthened for wetlands of all sizes, in turn protecting communities by retaining the important ecosystem services that are vital for biodiversity as well as human health and well-being, which wetlands provide,” Birch said.
The study, authored by Waterloo’s Waverley Birch, Michael Drescher, Jeremy Pittman and Rebecca Rooney (Biology, Faculty of Science), was recently published in the Journal of Environmental Management.