The Next 50 Years: Climate change and the Coastal Master Plan: “Hope for the best but plan for the worst”

By Dr. Doug Meffert, Executive Director, Audubon Louisiana

Louisiana’s 2012 Coastal Master Plan takes a realistic and critical examination of the effects of climate change impacts on the future of coastal Louisiana, both in terms of prioritization of restoration projects as well as risk reduction. In its “less optimistic scenario,” the master plan estimates 0.45 meters of sea level rise over the next fifty years. This is in addition to between zero and 25 millimeters per year of land subsidence, with the fragile deltaic plain having the highest rates. The resultant combination of sea level rise and subsidence predicts that relative sea level rise will be more than one meter during the next century in some areas of the Mississippi River Delta. Additionally, this scenario anticipates a 20 percent increase in storm intensity and a 2.5 percent increase in storm frequency for Category 1 hurricanes and greater. As climate change brings more severe storms and rising seas to Louisiana’s coast, it is important to incorporate these predictions into the formulation of the Coastal Master Plan.

Predicted land change over the next 50 years. Source: Coastal Protection and Restoration Authority of Louisiana (CPRA).

This “less optimistic scenario” predicts a very different and more vulnerable coast than we had in the 20th century. The master plan uses this scenario for its predictions for future flooding from a 100-year event and for prioritization of restoration projects, since what is labeled as “less optimistic” in the report could just as accurately be labeled as “increasingly likely.” This scenario is consistent with the recent assessments by the Intergovernmental Panel for Climate Change (IPCC), the findings from the Durban Climate Change Conference in November 2011, and more recently, peer-reviewed articles (Blum and Roberts, 2012; Day et al., 2012). In fact, one of the master plan’s Science and Engineering Board members, Dr. Virginia Burkett, was a coauthor of the IPCC’s 2007 report, which garnered the 2007 Nobel  Peace Prize for the IPCC.

“Hope for the best but plan for the worst” is the adage adopted by the Coastal Master Plan, and I couldn’t agree more. As it is, there is not enough sediment in the Mississippi River to offset the predicted land loss from relative sea level rise and erosion if we do nothing. This means we need to act now for a future coast that supports the fisheries, birds and other ecological services upon which we depend. We need to plan for a future coast that still provides a natural storm surge buffer for our cities, towns and critical infrastructure. That future coast will just be different than what we’ve known in the past. And that future coast depends on implementing large-scale river diversions with no further delay. We finally have a realistic master plan based on the best science possible. Now, we just need to implement it.