First real-world time-travel experiment shows ecosystem collapse due to climate change

Abstract Climate impacts throughout the 21st century are multifaceted and include heat stress, water scarcity, flood risk, and a threat to biodiversity and ecosystems. Predicting these impacts has been challenging, even if the trajectory of climate change is precisely known. To date, recourse has commonly been taken to modeling and paleoclimate studies, but these approaches have significant limitations. Here we examine coastal ecosystem change during 12 years of unusually rapid, albeit likely temporary, sea-level rise (> 10 mm yr− 1) in the Gulf of Mexico. Such rates, which may become a persistent feature in the future due to anthropogenic climate change, drove rising water levels of similar magnitude in coastal Louisiana and thus affected the ~ 15,000 km2 of coastal wetlands in this region. Measurements of surface-elevation change at 253 monitoring sites show that 87% of these sites are unable to keep up with rising water levels. We find no evidence for enhanced wetland elevation gain through ecogeomorphic feedbacks, where more frequent inundation would lead to enhanced biomass accumulation that could counterbalance rising water levels. We attribute this to the exceptionally rapid sea-level rise during this time period. Under the current climate trajectory (SSP2-4.5), drowning of ~ 75% of Louisiana’s coastal wetlands is a plausible outcome by 2070.