Incorporating Climate Change with Conservation Planning: a Case Study for Tidal Marsh Bird Conservation in Delaware, USA.
Department of Applied Economics and Statistics, University of Delaware, Newark, DE.
Northeastern USA tidal marshes provide critical ecological services, including carbon sequestration, water filtration, storm protection, erosion control, and wildlife habitat. Regardless of the services provided, salt marshes have been filled, drained, and degraded since European settlement and the unique wildlife dependent on these ecosystems requires immediate conservation action. Furthermore, global sea level rise has become the foremost cause of contemporary and future marsh loss. Sea levels have risen ~2 mm/year over the last century and predicted marsh losses due to sea level rise are estimated to be 0.5–1.5%/year. Increases in marsh flooding from sea level rise creates a real and immediate challenge to tidal marsh bird persistence and uncertainties surrounding sea level rise must be integrated into conservation decisions to have smart and proactive conservation planning. Decisions about how to allocate limited conservation funding are often subjective and lack quantitative and repeatable methodologies. To assist with the prioritization of salt marsh habitat, we tested two quantitative methods (benefit targeting and binary linear programming optimization), to determine the best combination of unprotected tidal marsh parcels that would yield the greatest conservation benefit. We used three budget level scenarios, $10M, $15M, and $20M to develop budget specific parcel portfolios based on benefit targeting and optimization, and used tidal marsh obligate breeding bird density as our conservation target. We used three sea level rise scenarios (0.5m, 1.0m, 1.5m) to estimate the land cover types that would remain within each selected parcel. The optimization method selected more parcels, protected more marsh area, and conserved more tidal marsh obligate birds, than the more traditional benefit targeting method. Total marsh area ranged from 7.2–9.6% greater and bird density ranged from 7.3–12.8% greater given the optimization method. When benefit targeting and optimization protected the same number of birds optimization provided a cost savings of $1.75M-$2.9M. All sea level rise scenarios inundated >95% of the wetland area on selected parcels. Agricultural land had the greatest amount of area remaining of any land cover type in all scenarios, ranging from 79.9 ha, 82.0% of total portfolio area ($10M–1.5m scenario), to 648.7 ha, 70.8% of total portfolio area ($20M–0.5m scenario). Optimization models can be used to develop comprehensive strategies that protect marshes with current core tidal marsh bird populations, however, increasing rates of inundation from sea level rise will likely lead to losses of existing wetland areas. The potential future benefits of adjacent agricultural lands to tidal marsh birds through marsh migration should be incorporated into optimization models for more effective conservation planning and spending of limited financial resources.