The value of US coral reefs for flood risk reduction

The value of US coral reefs for flood risk reduction
Coral reefs are under threat from overfishing, pollution, invasive species, and warming and acidification of oceans caused by climate change.

Reguero et al. 2021

This study assessed the value of coral reefs in the US for reducing flooding by modelling the effects of losing the top one metre of coral reefs across 3100 km of coastline. This level of vertical reef loss is possible over coming decades if threats to the reefs are not mitigated and restoration projects not scaled up. The study estimates that if reefs were lost to this extent, floods of the scale that currently only occur once every 100 years would occur 10x more often. It would also increase the 1-in-100-year flood area by 23%, leading to 62% more people suffering from flooding, 90% higher costs from damage to buildings, and a 49% increase in indirect economic costs. This translates, in absolute terms, as the top one metre of reef preventing 113km2 from flooding, protecting 54,000 people, and US$2.7 billion in property and US$2.6 billion in economic activity being saved.

The authors also found that reefs disproportionately protect minorities and low-income groups, although the largest absolute economic benefits were in highly developed areas such as Florida and Hawaii. The top one metre of reef prevents a 263% increase in annual flood risk for low-income groups in Puerto Rico, 127% in American Samoa and 120% in the US Virgin Islands, compared to the 77% national average.

Currently, funds for disaster management and climate change adaptation are tens to hundreds of times higher than those for habitat conservation and restoration. Therefore, valuing reefs for their contribution to flood risk reduction opens new funding opportunities for reef management and restoration, such as hazard mitigation, disaster recovery and insurance financing streams. Moreover, protecting and maintaining healthy coral reefs in many cases are a more cost-effective strategy for coastal flood mitigation than engineered, ‘grey’ infrastructure.

Read the full paper here.