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

Background/Question/Methods

There is a great deal of interest in enhancing multiple ecosystem services provided by agricultural lands, but little research has examined how management for specific ecosystem services affects other services. We are evaluating tradeoffs among ecosystem services in an existing PES pilot program in the Northern Everglades that is paying ranchers to retain water on their lands, to reduce flow into Lake Okeechobee.   In addition to water storage, ranchlands provide forage, corridors critical to wildlife movement, contain a mosaic of wetlands, native grasslands/savannas, and harbor common wildlife as well as threatened and endangered species.  In order to sustain multiple ecosystem services on ranchlands, relationships among ecosystem services and environmental stressors must be understood. The objectives of this project are: 1) evaluate the effect of water retention on other ecosystem services, such as biodiversity and forage quality; and 2) investigate the response of stressors, such as invasive species, to water management. Here, we focus on the relationships between hydrology, forage, native plants and invasive plants. We plan to set these results into the broader context of economic impacts and will consider several other ecosystem services and stressors to water management. The project will identify tradeoffs that will inform sustainable management of ranchland. 

Results/Conclusions

A non-metric multidimensional scaling ordination was used to assess plant species composition. In wetlands embedded in intensively managed pastures, composition changed along a hydrological gradient (R² =0.38, p<0.001), while along the same breadth of hydrological gradient, in natural rangeland, the relationship was weak (R² =0.05, p=0.007).  Non-native richness was significantly positively related to maximum water depth in natural rangelands (R²=0.75, p=0.011), but unrelated in intensively managed pastures (R²=0.03, p=0.73). These results may be due to a greater number of non-natives in intensively managed wetlands which are adapted to different areas along the hydrological gradient while in natural rangeland wetlands, most non-natives occur in deeper wetland zones.  These results suggest that the response of wetlands to increases in hydroperiod may depend on land-use.  In less disturbed wetlands, plant composition weakly changed across the hydrological gradient, but richness of non-natives was strongly related to maximum depth. In contrast, within disturbed wetlands, plant composition sharply changed across the hydrological gradient and non-native richness was unrelated to maximum depth.  This suggests that tradeoffs in ecosystem services may be context dependent.  A deeper understanding of relationships among these and other ecosystem services is important to develop decision support tools for sustainable management of agro-ecosystems.