Tradeoffs among ecosystem services in restored wetlands

Land management decisions frequently involve choices that reflect tradeoffs among ecosystem services. These tradeoffs are not always apparent, and land managers unknowingly may make decisions that diminish the value of some services while enhancing the value of others. Offset policies, such as wetland mitigation in the United States, rely on the assumption that ecosystems can be restored to provide a full suite of services. Wetlands provide many ecosystem services such as water quality maintenance, carbon storage, flood abatement, and biodiversity support. Our objectives were to describe tradeoffs among ecosystem services in mitigation wetlands and identify abiotic and biotic drivers underlying these tradeoffs. We measured denitrification potential, organic matter decomposition, herbaceous biomass, and soil organic content as indicators of nutrient storage and removal services in 30 mitigation wetlands in Illinois, USA. Additionally, we estimated surface-water storage potential, and, since wetlands provide valuable biodiversity support, we determined the species composition of plant, anuran, and avian communities. We found a positive relationship among biodiversity indicators for different taxa. Denitrification potential and surface-water storage potential were positively correlated. However, there was a tradeoff between biodiversity support and nutrient cycling processes; soil organic matter, biomass, decomposition rates, and potential denitrification were greater at less biodiverse sites. Our findings indicate that optimizing restored wetlands for nutrient storage and removal may come at the expense of biodiversity. It is unrealistic to expect all services to be maximized at a restoration site. Therefore, restoration practitioners should prioritize services based on needs and opportunities given local and watershed contexts.