Accelerated marsh erosion following the Deepwater Horizon oil spill confirmed, ameliorated by planting

Multiple studies have examined the effects of the Deepwater Horizon oil spill on coastal marsh shoreline erosion. Most studies have concluded that the spill increased shoreline erosion (linear retreat) in oiled marshes by similar to 100-200% for at least 2-3 years. However, two studies have called much of this prior research into question, due to potential study design flaws and confounding factors, primarily tropical cyclone influences and differential wave exposure between oiled (impact) and unoiled (reference) sites. Here we confirm that marsh erosion in our field experiment was substantially increased (112-233%) for 2 years in heavily oiled marsh after the spill, likely due to vegetation impacts and reduced soil shear strength attributed to the spill, rather than the influences of hurricanes or wave exposure variation. We discuss how our findings reinforce prior studies, including a wider-scale remote sensing analysis with similar study approach. We also show differences in the degree of erosion among oil spill cleanup treatments. Most importantly, we show that marsh restoration planting can drastically reduce oiled marsh erosion, and that the positive influences of planting can extend beyond the immediate impact of the spill.

Automated summary

Multiple studies have shown that the Deepwater Horizon oil spill results in increased shoreline erosion in coastal marshes. However, this study confirms that the oil spill significantly increased marsh erosion for two years, primarily due to vegetation impacts and reduced soil shear strength. The study also highlights the positive influence of marsh restoration planting in reducing erosion and its long-term benefits.