Assessing trade-offs among ecosystem services in a payment-for-water services program on Florida ranchlands

Background/Question/Methods

Enhancing ecosystem services provided by agricultural lands is of much interest, but little research has examined how management for specific services affects others. We evaluated trade-offs among ecosystem services in an existing payment for ecosystem services (PES) pilot program in the Northern Everglades that is paying ranchers to retain water on their lands.  In addition to water storage, ranchlands offer multiple ecosystem services, including forage production, a mosaic of wetland and upland habitats, and associated biodiversity. Our objectives were to: (1) quantify biodiversity and forage production on four ranches participating in the Florida Ranchland Ecosystem Services Project (15 wetlands); (2) evaluate whether enhanced water storage created synergies or trade-offs for the ecosystem services of biodiversity or forage production; and (3) determine whether enhancing water services affects stressors such as pests (mosquitoes) and invasive plants and animals, thus detracting from services provided. Ultimately, our data will refine decision tools to evaluate trade-offs among multiple ecosystem services at scales relevant to ranchers and decision makers.

Results/Conclusions

We used an information criterion approach to evaluate models describing the association between water storage, primarily measured as water depth; invertebrate and vertebrate abundance; plant richness; non-native plant cover; and wetland forage cover. We predicted that diversity of most organisms peaks at intermediate water depths, except fish, which were expected to become more abundant with increasing depth.

Total abundance of macroinvertebrates, amphibians, and fish generally increased with water depth and peaked at intermediate to high depths, ~10-35 cm. Non-native vertebrates were too rare to compare with water availability. Plant richness decreased with increasing water depth in all wetlands. Plants associated with short-hydroperiod, diverse wet prairies declined with increasing water depths. Significant quadratic relationships between water depth and non-native plant cover were found in four of 15 wetlands.  Our prediction that upland forage cover would decline with water depth was supported for all wetlands, but decreases in wetland grass cover (forage species) was not found at deeper depths. Our results suggest that managing for water services may create synergies and trade-offs with diversity depending on which organisms are considered.