Relationship Between GHG Reduction and SLR Land Loss in Louisiana

Coastal restoration planning in Louisiana has traditionally been based on a limited set of sea level rise (SLR) scenarios and has focused on slowing land loss in a sediment-starved deltaic system through large-scale restoration strategies such as marsh creation and sediment diversions. However, emerging global and local climate mitigation efforts raise an important question: to what extent could greenhouse gas emission reductions stabilize future SLR and thereby enhance the long-term effectiveness of coastal restoration projects? This study evaluates the influence of future emission pathways, associated temperature change, and SLR projections on land loss rates in coastal Louisiana, with a particular focus on the Barataria Basin as a pilot system. We compiled and synthesized recent literature on greenhouse gas emission scenarios and SLR projections from major scientific and policy frameworks, including IPCC, USACE, NOAA, the National Climate Assessment, and Louisiana’s Coastal Protection and Restoration Authority. Using a computationally efficient biophysical modeling framework, we conducted 240 numerical experiments to examine the sensitivity of coastal land change to a range of environmental drivers, including SLR rates (1–2 m by 2100), subsidence, freshwater inflow, sediment supply, organic accretion, and the timing of Mid-Barataria Sediment Diversion (MBSD) implementation. Results indicate that restoration outcomes are highly sensitive to future climate trajectories. Under lower SLR scenarios (approximately 1 m by 2100), the MBSD produces net positive land change through the end of the century, whereas under higher SLR scenarios (approximately 2 m by 2100), diversion benefits are substantially reduced, particularly if implementation is delayed. In the most severe scenario considered—delayed diversion operation and high SLR—nearly complete marsh loss occurs by 2100. These findings highlight the broad plausible range of restoration outcomes and underscore the critical role of emission reductions in improving restoration effectiveness. Overall, this study demonstrates that climate mitigation and coastal restoration are strongly interconnected and should be evaluated jointly. Incorporating emission-driven SLR uncertainty into restoration planning, alongside adaptive management and complementary strategies such as marsh creation and ridge restoration, provides a more robust framework for sustaining Louisiana’s coastal landscape under future climate change.