Co-benefits and possible unintended consequences of restoring wetlands for nutrient reduction

Issue

Agriculture is a leading driver of eutrophication, the enrichment of water with nitrogen (N) and phosphorus (P). Edge-of-field practices such as the construction or restoration of wetlands that intercept and process runoff offer important opportunities to mitigate nutrient losses. However, the differential effects of wetlands on N and P removal influence the ratio of these critical nutrients and the composition of biological communities both within wetlands and in their receiving waters. Wetlands serve a suite of ecosystems services and their importance for supporting biodiversity is well established; however, the biological value of wetland restorations can vary widely and there is much value to be gained if we can learn to design and maintain wetlands to better optimize their ecological functioning.

Objective

Researchers will quantify several biological co-benefits/consequences of edge-of-field nutrient reduction achieved by wetland restoration. First, we will assess the biodiversity of primary producers and their consumers in a series of restored Iowa wetlands to understand their biological and conservation values. Second, we will examine the effects of wetland nutrient reduction on downstream communities to investigate their ecological roles the landscape.

Approach

Researchers will apply a bioindicator approach using surveys of primary producers and invertebrates to evaluate wetland functioning and habitat quality in relation to differences in restoration design, nutrient availability, and other local conditions. By measuring biological responses immediately upstream and downstream of the wetlands, the team will also test how changes to water quality (including shifting nutrient ratios) influence communities in receiving waters and risks of harmful algal blooms.