Our results indicate water depth, surrounding agriculture footprint, and amount of precipitation received all significantly influence the water quality of prairie wetlands in Alberta. All three factors influence total phosphorus present, whereas only water depth and surrounding agriculture footprint influence total nitrogen. The different processes that influence the nitrogen and phosphorus cycles may explain their different responses to precipitation. While the nitrogen cycle in wetlands is mainly influenced by biological processes, the phosphorus cycle is governed by geochemical processes. Although our results show a decrease in phosphorus with an increase in precipitation, the opposite relationship was expected. Typically, precipitation increases sediment wetness which promotes the solubilisation of phosphorus present in the soil. However, phosphorus solubility is also negatively influenced by acidity. In areas with higher human footprint, precipitation may acidify wetland water, in turn, leading phosphorus to precipitate out of the water column into the sediment. This latter process may explain the lower total phosphorus we observed in prairie wetlands with higher precipitation.
Our finding that nutrient loading increases with agricultural footprint is consistent with other studies—nutrient amounts in wetlands are positively correlated to the proportion of agriculture in the surrounding watershed. These elevated nutrient loadings, however, do not always translate into a loss of biodiversity. In prairie wetlands in Alberta, the nutrient threshold beyond which biodiversity is affected has yet to be established; this is exactly what ABMI hopes to determine. We’re currently analysing the effects of adjacent land-uses on the aquatic plants and invertebrates of Alberta,
and will publish a follow-up ABMI Science Letter to speak to our results.
We found prairie wetland condition to be influenced by both landscape and local factors. Thus both of these factors must be considered when creating and evaluating
policy to effectively protect Alberta’s wetlands. One of the main focuses of the recently introduced Alberta Wetland Policy is to protect wetlands for the long-term benefit of
Albertans. The policy suggests environmental impacts on wetlands be avoided, and if not reasonably avoided, then minimized. Where wetlands have been degraded or lost and restoration or mitigation is necessary, our results indicate that managers should focus their efforts—when managing for adjacent land-use effects—on wetlands with appropriate morphometry.