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Row Crops. Are they Affecting Lake Ontario Watershed Health?

A key challenge for the agriculture sector is to feed an increasing global population, while at the same time reducing the environmental impact and preserving natural resources for future generations. Urbanization is in general known to change the land use in southern Ontario; turning agricultural land into commercial, industrial and residential areas often adversely affecting water quality in streams.

A recent study carried out by Trent University’s Environmental and Life Sciences Graduate Program and School of the Environment, supported by Environment and Climate Change Canada and the Ganaraska Region Conservation Authority, aimed to quantify land use/land cover changes within twelve Lake Ontario tributaries between 1971 and 2010. The study was completed also to determine whether these changes co-occurred with changes in total phosphorus (TP) and nitrate nitrogen (NO3-N) concentrations in streams (Max J. DeBues et al., 2019).

The Ganaraska Monitoring Report 2018 reports declines in stream TP and increases in NO3-N; however, the two nutrients have never previously been considered together, and the role of land use/land cover change has not been explicitly considered. The study by Trent University found that on a watershed scale, increases in row crop agriculture co-occurred with regional trends of total phosphorous decreases and nitrate nitrogen increases. The results highlight the interrelated connection of land, soil and water, and reminds us that food production requires long-term planning and multi-level governance components to build sustainable food systems.

Sustainable food production requires agricultural practices that improve soil health to maintain and provide fertile land for food production; which, in turn, play a key role in supplying clean water and building resilience to floods and droughts. For example, non-degraded soil captures and stores water, making it available for absorption by crops; and, therefore, minimizing surface evaporation and maximizing water use efficiency and productivity. Maintaining cultivated land, healthy soils and access to clean water is thus essential, not only to guarantee food production, but also for the resilience of the whole ecosystem.

Current intensive agricultural practices seem to lead to increased mobilization of synthetic fertilizers, which drive eutrophication causing algae bloom in water bodies. This affects aquatic life, and in the long-term, human health, due to continued water pollution. Perhaps, reshaping of some agricultural practices is required to reintegrate with the environment and to build climate resilient and healthy agricultural systems.

The full study can be found in the Journal of Great Lakes Research.

To learn more about watershed health, contact the Ganaraska Region Conservation Authority (GRCA) at 905.885.8173.

Written By: Dr. Jessica Mueller, GRCA’s Watershed Hydrogeologist