Effects of drought and wildfire on wetland ecosystem services in the Okefenokee National Wildlife Refuge, Georgia, USA

Background/Question/Methods

We focus on the need to consider recent and projected climatic variability in future estimates of ecosystem services, especially those in wetlands with fluctuating water levels. Because most wetland ecosystem services are not based on long-term studies nor traded in markets, estimates of their values are difficult to determine for comparative studies under conditions of climate change that include prolonged drought and wildfires. The National Wildlife Refuge (NWR) System includes diverse wetlands that differ in their capacities to provide ecosystem goods and services such as clean water, clean air, flood mitigation, carbon sequestration, and recreation. With limited conservation funds, identifying ecological and sociological variables that influence the value of ecosystem services supported by different wetlands is necessary to ensure efficient conservation plans well into the future.

Results/Conclusions

Our analysis of the Okefenokee NWRprovides the first estimates for the values of carbon sequestration in wetlands in this region. Our estimates of ecosystem functions were based on previously published rates of primary production, decomposition, and net ecosystem carbon storage in wood and peat deposits. We used a benefit transfer approach to estimate the per unit value of stored carbon without consideration of climate variability. We estimated the gross values of carbon storage using a methodology consistent with the 2006 IPCC Guidelines for Greenhouse Gas Inventories. This approach assumes steady-state carbon stocks that are divided into above-ground and below-ground pools, which are each divided into living and dead carbon. For the price component we considered estimates based on the Regional Integrated Model of Climate and Economy (RICE) 2011 model that proposed the 2015 estimated global social cost (Global Value) of carbon in the “business as usual” scenario  to be $13 per ton of CO2.  This approach indicates values of $140 per acre and the total value for the Okefenokee NWR to be $53 million per year.  These values are subject to inter-annual fluctuations in both the amount of carbon produced and stored because of climatic variability, especially if droughts and wildfires increase in frequency and duration. The values associated with mitigating greenhouse gases (CO2 and CH4) are also subject to potentially large variations. Nonetheless, this approach is likely to be useful in discussions with managers and planners who need additional parameters when deciding which tradeoffs can be most effective in establishing and sustaining protections for different types of wetlands.