Research by Ducks Unlimited Canada claims to have connected the dots between the continued loss of wetlands in Manitoba and increasing phosphorus loads into Lake Winnipeg.
Bob Grant, manager of provincial operations for Ducks Unlimited Canada, said the loss of wetlands upstream from the lake has the same effect as dumping 114 tonnes of commercial fertilizer, or 10 Super B truckloads, directly into the lake every year.
“Never before has DUC’s push to stop the loss of wetlands been so staunchly supported by research,” said Grant.
“Our results are by far the most compelling scientific support for the benefits that Manitoba’s wetlands provide to all Manitobans. In fact, this research has broad application across Canada and should be taken seriously by all municipal, provincial and federal governments.”
Read Also
British Columbia farmers to receive increased AgriStability supports
B.C. farmers to receive bump in AgriStability compensations due to weather concerns, international trade instability
Grant said up to 70 percent of wetlands have been lost or degraded in settled areas of Canada in the past century.
This has had a negative impact on the environment and arguably a large role in the eutrophication of Lake Winnipeg, a process in which an increase in chemical nutrients such as phosphorus spark excessive plant growth, choking out marine life.
To demonstrate how the loss of wetlands affects the environment, DUC partnered with the University of Guelph and Tarleton State University to study the Broughton’s Creek watershed, in the Rural Municipality of Blanshard north of Brandon.
The first phase of the project determined that 5,921 wetlands, or 70 percent of the total in the Broughton’s Creek watershed, were lost or degraded due to drainage between 1968 and 2005.
If the results of their research were scaled up to represent all southwestern Manitoba, wetland drainage has caused a staggering increase in phosphorus loads into Lake Winnipeg.
“Given that the province of Manitoba and the city of Winnipeg are investing millions of taxpayer dollars to reduce nutrient loading to Lake Winnipeg and to deal with climate change, stopping the continued destruction of wetlands should be a top priority,” said Pascal Badiou, a research scientist with DUC’s Institute for Wetland and Waterfowl Research.
Badiou pointed out that wetland destruction also results in significant economic costs due to downstream flooding, lost biodiversity, diminished ecotourism opportunities, lost groundwater recharge and the many other ecological functions that wetlands lose when drained or degraded.
Government policy should reflect that value, said Badiou, and landowners who protect or restore wetlands on their property should be paid from the public purse for providing long-term environmental services that benefit all citizens.
The figure of 114 tonnes of phosphate fertilizer being dumped into the lake was arrived at using the same method the province used in estimating the impact of various pollution sources on the lake, such as the hog industry.
“We know what certain land uses export in terms of nutrients. For example, we have a phosphorus-nitrogen export co-efficient for cropland, forest, pastures and grasslands and other land uses,” said Badiou.
“So, if you know the type of land that you’re draining, and the amount of additional land that is being drained, you can calculate the amount of nutrients entering into that stream. “
Looking at the land use changes on the Broughton’s Creek watershed over past decades made it possible to figure out the amount of increased nutrients making their way into the lake using a relatively straightforward mathematical formula, he added.
Badiou said that wetland drainage results in as much nutrient loading into Lake Winnipeg as all other human caused factors, such as fertilizer runoff, municipal and septic sewage combined.
“In the agricultural context, there’s a lot of blame being put on farmers for fertilizer runoff. But draining a wetland just compounds the problem,” he said.
“So we think that there are significant ways to reduce the problems that Lake Winnipeg is facing if we prevent wetland drainage and restore wetlands.”
Ranjan Sri Ranjan, an irrigation expert and professor of biosystems engineering at the University of Manitoba, has studied wetland drainage and restoration in projects across North America.
He said that the positive effects of wetlands as carbon and nutrient sinks are documented.
In the Manitoba climate, where rainfall and spring runoff events tend to be intense, intermittent and highly seasonal, wetlands act as “settling ponds” preventing nutrients from being exported downstream.
The myriad plant and animal species that thrive in wetlands then take up, sequester and recycle nutrients in dissolved and particulate forms, rendering them effectively immobile for long periods in places where they can do no harm.
“It is a win-win situation, and as an irrigation engineer by training, I know that finding reliable sources of water is important for farmers,” said Ranjan.
With funding from Agri-Food Research and Development Initiative, he is working on a project that will use tile drainage to remove excess water from farmland that is then stored in a constructed wetland on nearby marginal land.
In dry years, water flows through the tiles into the subsoil to optimize moisture levels for the crop.
The role of nutrients as limiting factors in crop production is well understood, he added, and farmers spend thousands of dollars on fertilizer every year to optimize yields.
But without adequate water, no crop can grow, he said.
