The Power of Small Wetlands for Clean Water

From 2017 to 2019, Ducks Unlimited Canada (DUC) and their conservation partners constructed 75 new wetlands and replaced infrastructure on an additional 17 existing wetland restoration projects in southwestern Ontario to improve the resilience of Lake Erie watersheds to climate change-driven increases in precipitation. The interactions between phosphorus loadings from agricultural runoff and climate change projections are complex but are primarily driven by the projected change in precipitation patterns. The rising nutrient load in Lake Erie, combined with other changes to Ontario’s climate, has triggered increasingly severe harmful algal blooms over the last decade causing significant financial, economic, and social impacts to communities in the Lake Erie basin. Following wetland construction, DUC implemented a rigorous monitoring program to determine the nutrient retention capacity and the nutrient reduction efficiency of these restored systems. The monitoring indicates that the restored wetlands act as important “phosphorus sinks,” with less phosphorus leaving the wetland basins than entering them. The implementation of these new wetland projects within the Lake Erie watershed is seen as significant accomplishment in contributing to the goals of the Canada-Ontario Lake Erie Domestic Action Plan.

Read the Summary Link to Full Case Study

Identifying Actions

The Lake Erie Action Plan identifies over 120 actions by Canada, Ontario and other partners, to meet binational 40% phosphorus load reduction targets. Wetlands are identified in the LEAP report as an important natural heritage feature in retaining and filtering runoff. The report also identifies the following priority actions:

  • Support watershed and nearshore-based strategies and community-based planning for reducing phosphorus loads.
  • Conduct research to better understand and predict the impact of climate change on the Lake Erie ecosystem

With wetland loss rates of more than 85% in many counties of southwestern Ontario, wetland restoration can play an important role in retaining non-point source phosphorus on the landscape. A changing climate increases the risk of phosphorus loss and the need for multiple best management practices to be selected for each site to maximize their effectiveness under variable conditions. The existing knowledge base for these practices and their collective impact needs to be updated as climate change progresses, consistent with an adaptive management approach. DUC is a leader in wetland conservation and restoration in Canada.

In 2017, DUC, in partnership with eight other conservation groups, identified candidate wetland restoration opportunities within the Lake Erie watershed and established a monitoring program to determine the nutrient retention capacity and the nutrient reduction efficiency of these restored systems. These restoration opportunities came directly from landowners who approached DUC or the conservation partner or were identified as part of another project being implemented on the property such as municipal drainage works, agricultural BMPs, or other stewardship activities. All project opportunities were first screened using desktop GIS tools to determine if a field site visit was warranted. DUC identified the 17 projects requiring the replacement of existing infrastructure based on engineering inspections and landowner feedback.

Implementation

Wetland restoration in the Lake Erie watershed supports the Domestic Lake Erie Action Plan recommendations related to reducing non-point sources of pollution that negatively impact the water quality of Lake Erie. With funding from Infrastructure Canada and the Ontario Ministry of Natural Resources and Forestry, $1,300,000 in funding was allocated to the two subcomponents of this project. Between 2017 and 2019, 75 new wetlands were constructed (69 in the Lake Erie watershed) and infrastructure was replaced on an additional 17 existing wetland restoration projects in the Lake Erie watershed. The new wetland projects ranged in size from 0.1 ha (0.3 acres) to 9.5 ha (23.4 acres) of restored wetland habitat. In addition to their restored wetland values, these projects are important for their ability to secure and protect additional existing wetlands and adjacent upland habitat under a conservation agreement, often times leading to additional stewardship opportunities.

Along with providing healthy landscapes for waterfowl, these new wetlands provide a multitude of additional ecological benefits to the landscape including helping to improve surface-water quality in southern Ontario. A monitoring program was established to determine the extent to which these restored wetlands have the potential to reduce phosphorus loads entering streams and rivers across the working landscape of southwestern Ontario and ultimately reduce phosphorus loading to Lake Erie.

Outcomes and Monitoring Progress

DUC’s Institute for Wetland and Waterfowl Research (IWWR) implemented the standardized wetland monitoring protocol for one water year beginning October 1, 2018 to assess the ability of newly restored wetlands to retain nutrients and reduce non-point source nutrient pollution in southwestern Ontario. This science was repeated again with a second water year of monitoring in 2021.The results from both studied years demonstrated that newly restored small wetlands are effective sinks of both total and dissolved forms of phosphorus and nitrogen, including soluble reactive phosphorus.

  • Results indicate the restored wetlands act as “phosphorus sinks,” with less phosphorus leaving the wetland basins than entering them.
  • Mean wetland retention capacity for phosphorus was determined to be 11.7 kg per hectare per year with a 46% overall mean reduction efficiency.
  • All eight wetlands efficiently captured soluble reactive phosphorus (SRP), the form of phosphorus considered most problematic for water quality in Lake Erie, with a mean SRP retention capacity of 4.8 kg per hectare per year, and a 60% reduction efficiency.
  • Restored wetlands were found to function in a nutrient retention role in all four seasons, an indication that restored wetlands can be effective to reduce nonpoint source nutrients from entering Lake Erie.

Next Steps

Through this work, DUC and its many conservation partners have made strong progress in driving a systemic change in approach toward watershed-scale wetland conservation, a natural solution that will be increasingly needed in the Great Lakes region and beyond. DUC science staff continue to study and plan for the potential impacts of climate change to ensure wetland and waterfowl management objectives are achieved and policy efforts that reduce the threat of climate change and enhance the resiliency and sustainability of wildlife and their habitats are implemented.

Resources

Link to Full Case Study

Additional resources:

Using climate change projections enables better adaptation decisions, as it allows you to better understand how the climate may change. To learn how to choose, access, and understand climate data, visit ClimateData.ca’s Learning Zone.
For more information on variables that may be useful in work related to marine management, visit ClimateData.ca and click “Explore by Variable” for future climate projections related to temperature and precipitation, which can be used to inform marine management.