Sea-Level Rise and Louisiana’s Coastal Wetlands

The effects of anthropogenic climate change – specifically sea-level rise due to ice melt and thermal expansion – are likely to threaten already vulnerable coastal wetlands in Louisiana according to a new study published in Nature Communications on Tuesday.

The study was conducted by Climate and Society 2010 alum Krista L. Jankowski and colleagues at Tulane University and relied on data from the Coastwide Reference Monitoring System to characterize vulnerability of Louisiana’s coastal wetlands to present-day rates of sea-level rise. According to the National Science Foundation, which funded the study, Jankowski and colleagues “analyzed measurements of shallow subsidence rates at 274 sites across the coast and combined these with published GPS-measurements of deeper subsidence rates. Adding published satellite observations of the rise of the sea surface in the Gulf of Mexico, they were able to calculate how rapidly sea level is rising with respect to the coastal wetland surface.”

Louisiana’s coastal wetlands (Photo credit: Torbjörn E. Törnqvist)

With relative sea-level rates calculated to be 4 times the global average, approximately 35% of wetlands in the Mississippi Delta are at risk of drowning while in the Chenier Plain, the westernmost portion of the state’s coast, nearly 60% of sites are at risk. The main source of vulnerability, according to Jankowski, is that “sites in the Chenier Plain have low rates of vertical accretion and many aren’t able to add material to the wetland surface quickly enough to keep up with rising sea-level.” Given the value of wetlands in providing ecosystem services such as wildlife habitat and protection from storm-surge, widespread loss could be devastating.

Jankowski’s Climate and Society background informed a key caveat included in the conclusions of the study. According to the article, “while the mean rate of sea-level rise in the Gulf of Mexico appears to have remained below the global mean over the past few decades, it is far from certain that this will continue to be the case in the future, considering, for example, increasing rates of Antarctic ice melt.” With projections of increased sea-level rise rates in coming years, Jankowski says, “the vulnerability of coastal Louisiana wetlands may be indicative of challenges for other coastal regions in the near future.”