How Reefs Protect the Land

Coral reefs buffer coastlines from the pounding of waves by absorbing most of the wave’s force. This protects nearby coastal property. Healthy coral reefs constantly grow and repair wave damage, providing continuous protection for adjacent coastline. Unhealthy reefs cannot grow fast enough, slowly eroding and exposing previously protected coastline to powerful waves.

Benefits of erosion control

There are several benefits to the protection provided by coral reefs:

• Protection of coastal property
• Protection of important ecosystems
• Protection from tropical storms
• Saves cost and maintenance of breakwaters

Protection of coastal property
Coral reefs slow waves that would otherwise break directly on the shore.  These waves can be destructive and damage unprotected sea-front property.

Protection of important ecosystems
Coral reefs also protect other ecosystems, like seagrass meadows and mangroves. These ecosystems provide us with many important ecosystem services like water purification and food.

Protection from tropical storms
Coral reefs also protect coastlines from tropical storms and tsunami. This protection is likely to become more important as climate change is predicted to make tropical storms more frequent and destructive.

Saves cost and maintenance of breakwaters
Breakwaters offer similar protection against erosion, but they cost up to
US$15 million per km to build. Breakwaters also require repair. In contrast, the protection offered by coral reefs is free, and a healthy reef repairs itself.

How tiny coral polyps protect the land

What is a coral? Although coral reefs resemble dead rock, they are actually a thin layer of living coral polyps stretched over the stony body of the reef. These polyps build the structure of the reef and repair damage to it.  Growth stops if the coral polyps die. Other organisms help reefs grow – coralline algae cements the reef framework together and can add reef strength. But a dead reef slowly erodes to expose the coastline to the full force of the waves.

Erosion and sustainability

Like many types of disturbance, the pounding on the waves can be good or bad.

Waves bring nutrients to the reef making it more productive. Wave action also creates different zones on a reef (see “Reef structure” for more information). These zones increase diversity by providing a variety of habitats for reef organisms.

However, too much wave action will eventually wear a coral reef to sand.

Sustainable coral reefs continue to protect the coast when they grow at a rate that matches (or exceeds) the rate of erosion. Unhealthy reefs cannot grow fast enough and slowly erode to expose coastlines to erosion.

References

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Chong, J. (2005, January 5). Protective values of mangrove and coral ecosystems: A review of methods and evidence. The World Conservation Union. PDF retrieved on 16 October 2008 from http://data.iucn.org/tsunami/docs/pr-values-mangrove-coral-ecosystems-methods-evidence.pdf

Hatcher, B. G. (1997). Organic production and decomposition. In Life and death of coral reefs (Birkeland, C. ed.). Chapman & Hall: New York.

Intergovernmental Panel on Climate Change. (2007). FAQs from Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S. et al (eds.)]. Intergovernmental Panel on Climate Change. PDF retrieved 18 June 2008 from http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_FAQs.pdf

Moberg, F. & Folke, C. (1999). Ecological goods and services of coral reef ecosystems. Ecological Economics 29(2): 215-233.

National Ocean Service. (2008, March 25). Importance of coral reefs. National Oceanic and Atmospheric Administration. Retrieved on 17 June 2008 from http://oceanservice.noaa.gov/education/kits/corals/coral07_importance.html

Suharsono, A. (2007). Resilient Nature, Resilient People. Research Centre for Oceanography. PPT document retrieved 18 June 2008 from http://regserver.unfccc.int/seors/file_storage/k85aaj1nc36qd0c.ppt

Wells, S., Ravilious, C. & Corcoran, E. (2006). In the front line: shoreline protection and other ecosystem services from mangroves and coral reefs. United Nations Environment Programme World Conservation Monitoring Centre (UNEP-WCMC). PDF retrieved 18 June 2008 from http://www.unep-wcmc.org/resources/PDFs/In_the_front_line_LR.pdf