Sea level rise and prescribed fire management: Implications for seaside sparrow population viability

Abstract

In the Chesapeake Bay, Maryland, unusually high rates of sea level rise threaten endemic tidal marsh birds, while prescribed burning benefits these bird populations. Effective conservation of tidal marsh birds requires that management actions be prioritized based on their impact to the long-term population viability for these species. We used a population viability analysis to evaluate the relative influence of two sea level rise scenarios and two prescribed fire management scenarios on the population viability of seaside sparrows, a tidal marsh obligate species, at Blackwater National Wildlife Refuge and Fishing Bay Wildlife Management Area. Marsh loss caused by rising sea levels had a greater impact on seaside sparrow population viability than did prescribed fire. Limiting marsh loss over the next 50years to 15% of the present extent caused a 19% probability of reaching the quasi-extinction threshold, while losing 33% of extant marsh caused a 50% probability of reaching the quasi-extinction threshold. Prescribed fire increased the likelihood of seaside sparrow persistence; increasing the amount of frequently-burned marsh from 12% to 53% lowered the quasi-extinction probability from 0.20 to 0.10. Slowing the rate of marsh loss will have a greater positive effect on seaside sparrow viability than increasing the frequency of prescribed fire. Sea level rise poses the single greatest threat to the long-term persistence of tidal marsh bird populations.