How high? Identifying elevation thresholds to guide coastal marsh restoration

Introduction

Coastal marshes are highly valuable ecosystems facing threats from rising sea levels and intensifying storm events. To elevate marsh surfaces and prevent loss of ecosystem services, the beneficial use of dredged material (BUDM) is increasingly being implemented across the United States.

Objectives

The objective of this study was to aid decision-makers and restoration practitioners by identifying elevation thresholds that control the optimal function of Spartina patens-dominated marshes along the Texas Coast.

Methods

This study was conducted in the coastal marshes of the J.D. Murphree Wildlife Management Area (Texas). We collected elevation and vegetation cover data along ecological transition zones in marshes nourished with BUDM to identify elevation thresholds that define zones of optimal plant survivorship and growth.

Results

We identified lower (−0.05 m mean high water, MHW) and upper (0.26 m MHW) elevation thresholds that defined transitions to open water and unvegetated bare ground, respectively. Elevation targets (T) and elevation target zones, which defined areas with the greatest vegetation cover, were determined for S. patens (T: 0.11 m, target zone: −0.06 to 0.26 m MHW), S. alterniflora (T: 0.00 m, target zone: −0.12 to 0.10 m MHW), and Distichlis spicata (T: 0.17 m, target zone: 0.07–0.25 m MHW).

Conclusions

Our analyses provide species-specific elevation targets for coastal marsh restoration through BUDM, which can improve restoration outcomes for coastal wetlands.