Global protection from tropical cyclones by coastal ecosystems - past, present, and under climate change

Sarah Hülsen , Robert I. McDonald, Rebecca Chaplin-Kramer, David N. Bresch, Richard Sharp, Thomas Worthington, Chahan M. Kropf 

Coastal ecosystems have the potential to contribute to disaster risk reduction and adaptation to climate change. While previous studies have estimated the value of current coastal ecosystems for reducing coastal risk, there have been relatively few studies that look at changes in ecosystem service provision, in the past and under climate change. We employ the probabilistic, event-based CLIMADA platform to quantify the protection from tropical cyclones provided by coastal ecosystems, modeling the number of beneficiaries in the past and under future climate change. We also investigate the potential of Nature-based Solutions (NbS), such as mangrove restoration. We find that currently, one in five (21%) of all people impacted annually by tropical cyclones in the global low-elevation coastal zone is within the protection distance of coastal ecosystems. Over the last 30 years, the share of protected people has decreased by approximately 2%, due to ecosystem loss. With climate change, the average annual number of people impacted will increase by 40%. Simultaneously, the proportion of people protected by coastal ecosystems with climate change decreases due to changes in tropical cyclone distribution (-1%). The importance of current coastal protection, and the potential for increasing protection by NbS, varies widely between countries. While the number of people protected globally only increases slightly with mangrove restoration, protection in individual countries can increase by up to 39%. Our findings provide a basis for NbS planning and adaptation policy, by highlighting areas which will be crucial for coastal protection services in a world altered by climate change.