Evaluating trade-offs and co-benefits among biophysical and cultural ecosystem services in freshwater wetlands variably impacted by groundwater extraction

Background/Question/Methods

Freshwater wetlands provide valuable supporting and regulating services like carbon storage, flood mitigation, and habitat for native species as well as cultural services like recreation and aesthetic value for the surrounding community. When wetlands are affected by large or persistent disturbances, such as groundwater extraction, trade-offs among these services can occur. While relationships among biophysical services and variability in public perceptions of wetlands have been documented separately, there have been limited integrative studies that examine trade-offs or co-benefits among both biophysical and cultural services. This study proposes a novel approach: to measure biophysical services, through soil and plant sampling (n=30 wetlands), as well as cultural services, through online and in-person surveys (n=482 surveys). It assesses the following research questions: 1) how has historic groundwater extraction rates influenced the ecosystem services of wetlands; 2) what trade-offs or co-benefits have emerged among biophysical and cultural services? The Tampa Bay region hosts numerous wetland complexes found within areas that serve the dual purposes of a wellfield, or designated area for groundwater extraction appropriated for the drinking water supply, and a publicly accessible park, where frequent visitors can observe changes to wetlands over time making it the ideal place for this interdisciplinary study.

Results/Conclusions

Results indicate significant (p< 0.1) trade-offs between groundwater extraction (a provisioning ecosystem service) and plant biomass (ρ = -0.26), presence of native tree species (ρ = -0.23), and soil carbon and nitrogen storage (ρ = -0.36 and ρ = -0.44, respectively). Wetlands exposed to groundwater extraction had 17% lower basal area, 28% lower soil carbon and nitrogen storage and an almost 40% increase in soil bulk density compared to reference wetlands. Resident preference was highest in wetlands with visible water, diversity of trees, and limited understory, indicating synergies among aesthetic value, nutrient retention, and tree diversity. Additional cultural services derived from wetlands and surrounding parks included physical activity (95% of participants), getting close to nature (81%), and observing plants and wildlife (79%). This research proposes innovative methods for integrating social and natural science data to address the persistent challenge of balancing human and environmental needs in urban spaces that other cities can utilize to manage these same issues. Depressional wetland protection status under the Clean Water Act is again up for debate at the Supreme Court and this research provides evidence for the loss of ecosystem services that can occur without protections from human activity like overpumping groundwater.