Quantifying Coastal Flood Risk: How Mangroves and Reefs Defend Vulnerable Shorelines

Measuring Coastal Flood Risk

Researchers have managed to quantify the exact financial and human protection offered by the simultaneous presence of mangroves and coral reefs. Previously, calculating the benefits of this dual-defence mechanism against extreme sea levels had not been achieved. As global temperatures rise, predicting and mitigating coastal flood risk has become an urgent scientific priority.

Advancing Previous Models

While earlier studies investigated global flood risk, they did not quantify the specific benefits provided by the simultaneous presence of both mangroves and coral reefs under climate change. This new approach advances the field by utilising process-based inundation modelling.

By running simulations with and without these combined ecosystems, the researchers measured physical flood extents and mapped them against projected population and asset changes under future socio-economic conditions for 2030 and 2050. Because the future figures are based on specific modelling scenarios, the financial figures should be treated as rigorous estimates dependent on those pathways.

Billions Saved by Natural Defences

The study measured a reduction in global expected annual flood damage of USD 1.7 billion (12.9%) during the baseline period between 1980 and 2014. By 2050, under the SSP5-8.5 high-emissions scenario, the models suggest this protective benefit could rise to USD 2.7 billion (13.9%) annually.

The simulations indicate that by mid-century, the presence of these combined ecosystems could prevent:

• The flooding of 7,811 square kilometres of land.
• Damage to USD 45.8 billion in physical assets.
• The displacement or endangerment of 1.6 million people per year.

The Scope of the Projections

Despite the rigorous methodology, this research relies on specific socio-economic parameters. The future projections are modelled specifically under the SSP5-8.5 scenario. Consequently, the projected USD 2.7 billion in savings and the protection of 1.6 million people are tied directly to this particular high-emissions trajectory.

Furthermore, the results focus on how the spatial distribution of these ecosystems reduces coastal flooding on a broad scale, estimating global and regional trends rather than predicting exact inundation outcomes for individual, highly localised storm events.

A Defence Strategy for Vulnerable Nations

The data clearly shows that the benefits of these ecosystems are concentrated in countries with high climate vulnerability and low adaptation readiness. This implies that ecosystem degradation would raise future flood risk most where adaptive capacity is lowest. These findings provide a strong argument that mangrove preservation and reef conservation directly support climate change adaptation.