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

New study shows annual costs soaring to $272 billion, sending a powerful signal about reefs and their importance during the International Year of the Reef

aerial view of coral reefs

Coral reefs serve as natural, submerged breakwaters that reduce flooding by breaking waves and reducing wave energy. Aerial imaging and mapping of critical reef habitats in the Caribbean is being conducted by the Nature Conservancy and the Carnegie Airborne Observatory. (Photo by Emily Vacchiano)

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 against coastal flooding in countries around the world, are being lost rapidly. A new study investigating how much people and property are protected by coral reefs, and what is at stake if our reefs are lost, shows that coral reefs cut the cost of all flood-related damages around the world in half.

Published June 12 in Nature Communications, the study (“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 worldwide. Coral reefs serve as natural, submerged breakwaters that reduce flooding by breaking waves and reducing wave energy. The study compares the flooding that occurs now with the flooding that would occur on coastlines with coral reefs if just the topmost 1 meter of living coral reef were lost.

Significant losses of coral reefs are already happening, according to first author Michael Beck, research professor of ocean sciences at UC Santa Cruz and lead marine scientist at the Nature Conservancy.

“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,” he said. “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.”

Without living coral reefs, the annual expected damages from flooding would double, increasing by $4 billion. The costs from frequent storms would triple. If coupled with sea level rise, flooding could quadruple. For the big 100-year storms, flood damages could increase by 91 percent to $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 coauthor Íñigo Losada at the Environmental Hydraulics Institute of the University of Cantabria, Spain. “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 $400 million for each of these nations. The United States also receives many benefits from coral reefs (ranking 8th globally), with almost $100 million annually in direct flood reduction benefits. In addition to helping alleviate costs related to flooding, coral reefs also offer other economic benefits from tourism and fisheries. Per capita, the study found that reefs provide the most benefits to small island states, including the Cayman Islands, Belize, Grenada, Cuba, Bahamas, Jamaica, and the Philippines.

In just the past few years, tropical storms such as Hurricanes Irma and Maria and Typhoon Haiyan have had devastating impacts, and the effects of such storms would be even 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,” said coauthor Borja Reguero, a research scientist at UC Santa Cruz. “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.”

The flood savings from coral reefs can be directly used by governments in disaster recovery planning, for example, and by businesses such as insurance. This work also provides a clear case for better reef management. The researchers 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 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.”