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Reef
Restoration and Shore Protection In most of the tropics the finest protection of the coast is provided by healthy coral reefs. Wherever reefs are degraded by loss of corals (the only organisms capable of building the solid reef framework), the wave energy no longer absorbed by the reef increases its force on the shore, washing away beaches, seawalls, jetties, piers, trees, roads, and buildings. The costs of seawall protection varies a great deal according to whether rock aggregate is available, labor, transport, etc., but often runs around $10,000 per metre of coastline protected (around $10 million per kilometre or around $1 billion per hundred kilometres of shore). This is similar to the amount it cost the Maldives to build concrete sea walls around the capital island Male, after the island was flooded in 1987 subsequent to coral reefs being mined out for construction material. Around the world increasing beach and land erosion problems are being seen along inhabited shores because reefs have been damaged by mining, dredging, sewage, pollution, or sediments. The losses are worst where there are the largest investments in coastal docks, roads, and buildings. Areas subject to such erosion cost tremendous amounts to protect, and all structures built are ultimately undermined and broken apart by waves, when they must be rebuilt at great expense. In many such areas shore protection can be provided by building mineral accretion structures on basement rock to increase growth of corals and grow a steadily stronger structure which absorbs wave energy. Because mineral accretion artificial reefs produce limestone sand from rapid growth of calcareous algae, they also provide new material to renourish beaches. Artificial reef breakwaters built in the Maldives cost as little as one fiftieth as much as concrete breakwaters, and would be effective in many other coastal areas. The method works in areas of full strength seawater, so only regions which have large amounts of fresh-waters from rivers are inappropriate due to inadequate dissolved minerals. The efforts of the Global Coral Reef Alliance are focused on developing projects using mineral accretion to restore damaged reefs and grow breakwater reefs to protect coasts now eroding in the atoll island nations of the Indian Ocean and Pacific, because of the great threat that global sea level rise poses to these low lying countries. If sea level rise increases beyond the current global average of 2 millimeters per year most coral reefs will be unable to keep pace, and mineral accretion will be needed on a large scale to protect coastlines of entire countries against climate change. For more information on mineral accretion shore protection projects please contact GCRA.
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