In 2019, the U.S. Geological Survey published a detailed study into the economic value of coral reefs in the United States. The results were incredible. The study found that coral reefs provide natural flood protection to more than 18,000 people, which contributed an estimated value of $1.8 billion worth of coastal infrastructure and economic activity every year. The extent of this flood protection is likely to save lives, help reduce the poverty risk for many people, minimize damage to property and limit the risks from natural flood events. Obviously this is an amazing contribution to society, the economy and the environment. In this blog post we will discuss how coral are able to mitigate flooding and detail more about the incredible benefits this has.

The Economic Impact of Corals Mitigating Flooding

The U.S. Geological Survey study revealed that coral reefs in U.S. waters, from Florida, the Caribbean, Hawaii to Guam, contribute more than $1.8 billion in flood protection benefits every single year. Through mitigating the direct flood and subsequent risk of damage to public and private infrastructure, coral reefs provide another $800 million annually and help avoid additional cost of life and livelihoods by yet a further $1 billion. Whilst some may value reefs for their mere existence, capturing the economic value through rigorous valuations of reef benefits in this way is the first step toward mobilizing the resources needed to protect them.

Acting As Wave Breaks To Block Floods

Reefs are behaving like underwater breakwaters. They’re “breaking” waves and draining out their energy offshore, away from coastal properties and towns to prevent flooding. This is a very useful function, which scientists and government organizations are keen to explore further. Particularly as tropical storms alone in 2017 caused more than $265 billion in damage throughout the United States. Manmade defenses, such as sea walls, can destroy neighboring environments and endanger the species that rely on these ecosystems. Coral reefs, on the other hand, improve their surroundings by protecting shorelines and promoting healthy fisheries as well as recreational activities too. The effects of flood protection that reefs have in the U.S. are mirrored in more than 60 other countries around the world. It is estimated that the global cost of storm and flood damage to the world’s coasts would likely double without coral reefs.

Local Flood Protection Value

The estimation of the importance of flood protection from reefs employed state-of-the-art instruments used by engineers and insurers to determine flood hazards and benefits. Flood risk maps were developed to forecast the magnitude and depth of the floods that will arise in multiple hurricanes, both frequent and catastrophic, with reefs present and then without them. This was done using a model and more than 60 years of hourly wave data for all U.S. states and coral regions, an incredible combined area of more than 1,900 miles. Values for each individual 100 m2 grid cell were calculated, that’s roughly the size of a small house. Coupled with U.S. Census data as well as data from the Federal Emergency Management Agency, this allowed the researchers to identify infrastructure and people potentially at greater risk, that would particularly benefit from the presence of offshore coral reefs.

With fine-scale detail, this provided the researchers to pinpoint exactly who and where is provided with the flood defense provided by coral reefs. In Florida, for example, more than $675 million is gained in annual flood-protection from reefs. Another example is Honolulu, which receives $435 million worth of protection against a 1-in-50-year storm (i.e. an event likely to occur once in a 50-year period).

Investing In Natural Defenses

Coral reefs are under threat as a result of climate change, which is warming seas and causing coral bleaching. Pollution and overfishing also present serious threats to reefs globally and are causing significant harm. The UN study on biodiversity depletion states that live coral reef cover has declined by almost 50% since the 1870s. If this trend continues, at least 100-300 million people in coastal areas are at risk due to loss of coastal habitat protection alone. Not including the other likely impacts on food security. 

How will this valuation aid the conservation of coral reefs? Firstly, it highlights that hurricane relief funds should be used in part to provide financial support to rebuilding natural coastal defenses. Only about 1% of recovery funds went into restoring natural resistance after Hurricane Sandy in 2012, amid subsequent studies finding that marshes in the Northeast could help mitigate flood damage by some 16% annually. Over $100 billion has been spent recovering from hurricanes Harvey, Maria and Irma. If part of this funding was redirected towards fortifying coral reefs, this may provide a longer-term investment than flood infrastructure. 

This report also points to the role insurance companies could play in offering incentives to support nature-based defense schemes to reduce flood risk. Many insurance providers are consider habitats in industry risk models and to create opportunities to insure nature. Whilst this outcome may be unexpected, it provides a solution to protecting and even re-building coral reefs due to their proven flood protection benefits.

Another key player are federal agencies. Military bases also receive protection from reef ecosystems and have incentives available to invest in reef protection for critical infrastructure. These bases extend across the U.S. coastline and already initiatives including Engineering With Nature are making more use of natural solutions to minimize flood risks. Similar programs are already underway to restore marsh habitats led by the U.S. Department of Transportation to protect coastal highways with nature-based solutions. Both of these projects hint at the potential for these programs to extend to coral reefs. 

Coral reefs help defend cities and coastlines from natural disasters through flood mitigation. Coral reefs are essential to a wide range of aquatic species. With so much to lose, if immediate action is not taken to fund the protection and conservation of reefs, these valuable ecosystems could be lost forever.