Mapping High Marsh along the Northern Gulf of Mexico Coast

Submitted by atripp on Thu, 06/03/2021 - 10:08

Although extensive work has been devoted to understanding the role of fire in maintaining ecosystem functions in upland systems, little research has focused on understanding the impact of fire on coastal wetlands or the response of birds to fire in high marsh wetlands. High marsh is a unique habitat type threatened by sea-level rise and characterized by a community of specialized emergent vegetation that tolerates irregular tidal inundation. Land managers’ decisions about prescribed fire in high marsh systems are complicated by uncertainty around the response of birds to the application of prescribed fire. Without an understanding of how prescribed fire impacts high marsh ecosystems, including several high-priority bird species, natural resource managers will be limited in their ability to manage and conserve the biodiversity of the Gulf Coast.

In response, a new multidisciplinary project will investigate the effects of fire on Gulf of Mexico marshes by mapping high marsh and monitoring black rail (Laterallus jamaicensis), yellow rail (Coturnicops noveboracensis), and mottled duck (Anas fulvigula) responses to prescribed fire application using an adaptive management framework. The framework will inform decisions by helping researchers and resource managers test predictions and improve the understanding of how these birds interact with high marsh ecosystems and prescribed fire. This project, led by Mississippi State University, includes co-investigators and collaborations with 12 universities, Federal and State agencies, and non-governmental organizations.

Scientists from USGS Wetland and Aquatic Research Center and Mississippi State University are collaborating on the high marsh mapping associated with this project. This effort will include two components. The first component is developing a rapid high marsh potential dataset. Light detection and ranging (lidar) and tide data will be used to refine existing marsh habitat maps and produce a rapid high marsh potential dataset for the northern Gulf of Mexico coast. This process will involve using Monte Carlo simulations to develop probabilistic outputs for high marsh delineation. These data will be used to assist with site selection for avian monitoring efforts in subsequent years for this project. The second component is developing a contemporary high marsh habitat map. Although elevation is a major factor in determining the distribution of high and low marshes, zonation within salt marshes is complex and influenced by topography and groundwater hydrology. This component will involve satellite imagery, including Sentinel-2 imagery, which has reflectance in three red edge bands, and the aforementioned lidar-based probabilistic outputs to produce contemporary maps of high marsh for the northern Gulf of Mexico coast. Both map products will be validated with real-time kinematic GPS and vegetation assessments.

Spartina patens–dominated high marsh in Grand Chenier, Louisiana, in 2019. (Credit: Rachel Villiani [USGS] used with permission).

Author Name
Nicholas M. Enwright
Author Email