Fire in Coastal Marshes: History and Recent Concerns

Nyman, John; Chabreck, Robert

Fire is a traditional management tool in coastal marshes and is an important part of this ecosystem. This paper reviews the role of fire in coastal marshes of the southeastern United States and explores future concerns. Fire prevents some tidal fresh marshes from being invaded by woody species and increases the production of preferred wildlife food plants in some brackish and intermediate marshes. These goals are best achieved by burning during fall or winter during a moderate, steady wind when water is on the marsh surface. Spring and summer burning interfere with plant growth and harm newly born wildlife. Some fires are apparently set year round in the mistaken belief that all fire benefits the marsh. Organic matter produced in marshes is an important part of estuarine trophic cycles, but how burning affects organic matter export to estuaries is unknown. Burning generally increases plant production, but that will not benefit estuarine food chains if the extra production is merely burned the next year. A cautious approach would be to burn often enough to maintain high plant production and create desired plant communities, but infrequently enough to allow litter build-up that could be exported by storm tides. It is not known how burning affects vertical accretion, which is the gradual formation of new soil on the marsh surface in response to subsidence and sea-level rise. Vegetation eventually drowns without accretion. Accretion depends on peat accumulation in Gulf Coast marshes, although mineral matter may be more important elsewhere. Burning might reduce vertical accretion if peat production is reduced. However, burning might enhance accretion if burning increases root production. Burning frequency will likely determine whether the effect is positive or negative, but this has not been studied.