Research published today in the prestigious journal Nature Water found that widespread application of the common farm fertilizer, urea, severely degrades water quality in the Canadian Prairies.
Researchers at the University of Manitoba and the University of Regina added urea to farm ponds to simulate the effects of agricultural fertilization in the southern Prairies. Urea increased growth of microscopic plants (algae) to levels 10 times higher than seen in other damaged ecosystems, such as Lake Winnipeg in Manitoba. The researchers found that the excess algae also drained essential oxygen out of the ponds.
When compared with hundreds of similar water bodies across southern Saskatchewan, the study showed that nearly half of all Prairie lakes, wetlands, and reservoirs may be degraded by decades of urea use.
Dr. Cale Gushulak, lead author of the research paper and an assistant professor at the University of Manitoba says that the team's findings also revealed that agricultural regions in China and the United States are equally vulnerable to damage by urea use. "Our findings help explain why surface waters around the world are experiencing rapid oxygen loss that kills fish, increases toxin exposure, and intensifies harmful algal blooms, pushing freshwaters to an ecological tipping point," says Gushulak.
Dr. Peter Leavitt, limnologist and founding director of the Institute for Change and Society at the University of Regina, co-authored the report and says that urea accounts for over half of global fertilizer use and is considered safe because it's non-toxic at concentrations ten times higher than those used in the research team's experiment. "Rather, the damaging effects of fertilizers are being increased by draining natural wetlands that are important biological filters, capturing runoff from farms before it enters rivers and lakes."
The study shows that use of urea by farmers is not the problem.
"Rather, it's wetlands mismanagement that excessively drains farmland and increases fertilizer export to freshwaters," says Leavitt. "And Saskatchewan is one of only regions in the world to actively promote wetlands drainage."
The researchers say this is a global problem
"Two-thirds of the world's population is supported by urea and other nitrogen fertilizers—so we cannot, and should not, stop its use," says Gushulak. "However, if the fertilizer is lost from the soils, and ends up degrading surface water, then everyone loses"
Gushulak says that Manitoba also heavily fertilizes with urea and lakes and wetlands in the province have also likely been impacted by this practice.
The Prairie Provinces are known for their high agricultural productivity due to fertile soils and short but intense growing seasons. Sustainable healthy sources of water are needed for all agriculture, but these resources are threatened across the Prairies due to ongoing agricultural impacts, drainage of wetlands, and climate change.
Read the full study at: https://www.nature.com/articles/s44221-026-00636-7
