Without coral reefs, annual flood damages from storms could double globally

Coastal development and climate change are increasing the risk of flooding for communities across the globe.  Coral reefs, which provide a first line of defense to countries around the world, are being lost rapidly.  A new paper, published today in Nature Communications, values just how much people and property are protected by coral reefs, and what is at stake if our reefs are lost. Overall, the study shows that coral reefs cut the cost of all flood-related damages around the world in half, sending a powerful signal about reefs and their importance during this International Year of the Reef. 

 The Global Flood Protection Savings Provided by Coral Reefs uses models commonly applied in the engineering and insurance sectors to quantify and value the flood reduction benefits provided by coral reefs world wide – the first time a study of this magnitude has been conducted.  Coral reefs serve as natural, submerged breakwaters that reduce flooding by breaking waves and reducing wave energy.  This study compares the flooding that occurs now with the flooding that would occur on coast lines with coral reefs if just the topmost 1 meter of living coral reef were lost; losses that are already happening globally.

“Unfortunately, we are already losing the height and complexity of shallow reefs around the world, so we are likely already seeing increases in flood damages along many tropical coastlines," said Dr. Michael W. Beck, Lead Marine Scientist for The Nature Conservancy and Research Professor at UC Santa Cruz. “Our national economies are normally only valued by how much we take from nature. For the first time, we can now value what every national economy gains in flood savings by conserving its coral reefs every year.”

What are some of these values? Without our living coral reefs, the annual expected damages from flooding would double - an increase of US $4 billion.  The costs from frequent storms would triple. If coupled with sea level rise, flooding could quadruple.  For the big 1 in 100 year storms, flood damages could increase by 91% to $US 272 billion. 

“We built the best global coastal flooding model and then we added reefs to estimate flood risk overall and the benefits provided by these habitats,” said Professor Íñigo Losada, from IHCantabria at the University of Cantabria. “This represents the first global application of a coastal protection model that probabilistically estimates risk and the benefits of coastal ecosystems.”

The countries with the most to gain from reef conservation and restoration are Indonesia, Philippines, Malaysia, Mexico, and Cuba; annual expected flood savings exceed $400M for each of these nations. The US also receives many benefits from coral reefs (ranking 8th globally), with almost $100M annually in direct flood reduction benefits. In addition to helping alleviate costs related to flooding, coral reefs also offer other economic co-benefits like tourism and fisheries. Per capita, the study finds that reefs provide the most benefits to small island states including the Cayman Islands, Belize, Grenada, Cuba, Bahamas, Jamaica and the Philippines.

When we consider the devastating impact of tropical storms in just the past few years such as Hurricanes Irma and Maria and Typhoon Haiyan, the effects would be much worse without coral reefs.  Unfortunately, reef habitats across the world have been significantly degraded, and face growing threats from coastal development, sand and coral mining, destructive and excessive fishing, storms, and climate-related bleaching events. 

“These estimates make a compelling case for present-day spending on reef management without assuming that reefs will disappear altogether under a business as usual scenario - nor do they rely on just rare, large storms. Better valuations of the benefits provided by coastal habitats like coral reefs, provided in terms familiar to decision makers, can help decision makers recognize the value and ensure the protection of these critical habitats and their services,” said Dr. Borja Reguero, a Research Scientist at UC Santa Cruz.

The flood savings from coral reefs can be directly used by governments, for example, in disaster recovery planning, and by businesses such as insurance. This work also provides a clear case for why we must manage reefs better, and we have already begun working with disaster agencies and the insurance industry, including FEMA, the World Bank, Munich Re, Swiss Re, and Lloyd’s, to use these results to inform funding decisions and insurance tools that can support reef restoration for risk reduction. The results from these analyses are mappable and downloadable on the Natural Coastal Protection app at http://maps.oceanwealth.org/.

“Coral reefs are living ecosystems that can recover if they are well-managed, and this study identifies why and where we should find the needed support for restoration and management,” said Beck. “It is our hope that this science will lead to action and greater stewardship of reefs around the world.”