Coral reefs provide the first line of defense for 63 million people in 100 countries across the globe who live in coastal and low-lying areas.
—Atlas of Ocean Wealth (Spalding et al. 2016)
The wave attenuation benefits of coral reefs are comparable to artificial defenses. However, coral reefs are self-sustaining ecosystems, meaning that – if healthy – reefs continue to grow and protect shorelines without assistance from humans. Manmade structures, in contrast, require regular maintenance making them more expensive over time (Simard et al. 2016). Thus, coral reefs are a more cost effective, sustainable solution to provide coastal protection, but need to harbor healthy corals that grow and reproduce for these benefits to continue.
Coral reefs protect coastal people and property by acting like natural breakwaters. This occurs because bottom friction increases as waves move across reefs, causing waves to break and disperse their wave energy (Gourlay 1994, 1996a,b; Hardy and Young 1996). Healthy reefs dissipate wave energy by up to 97% (Ferrario et al. 2014), reducing storm surges and helping maintain shorelines by mitigating erosion and supplying and trapping sediment on beaches.
By reducing exposure to waves, flooding, and erosion, and by providing social, economic, and ecological benefits before, during, and after catastrophic events, coral reefs act as a first line of defense for coastal communities.
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