An artificial reef is a human-made underwater structure that closely approaches or extends above the surface of the water. These reefs provide excellent habitats for marine life and are often built specifically for this purpose. In addition, reefs protect nearby beaches from erosion. Historically, man-made reefs have also been used to protect against naval invasion by providing an underwater barrier to prevent passage or sink unwary invading ships.
As almost any material can be used to construct an artificial reef, several creative solutions have been carried out that promote a type of conscientious littering of the ocean floor. Programs that create reefs from ships that are unworthy for sea travel provide excellent sites for ocean life while reducing the huge amounts of solid waste that result from the deconstruction of vessels. These reefs are particularly beneficial in flat areas of seafloors that provide no natural surfaces to which animals like barnacles, clams, and corals may attach. Through these programs, a ship may be scuttled only after all materials that may present a risk to oceanic life are removed.
Likewise, owners of offshore oil rigs slated for decommission are frequently presented with the opportunity to save money by turning the structure into an artificial reef. The companies benefit because the cost of cleanup of the structure and surrounding area is small compared to a massive removal effort. In addition, the bases of the rigs often already support abundant sea life, so these programs essentially help conserve existing ocean habitats while encouraging further growth. It should be noted, however, that the actual sinking of the rig often temporarily disrupts existing reef life.
The construction of an artificial reef can also provide environmental conservation of a different type. Reefs can act as barriers to reduce the strength of waves as they approach the shoreline. Weaker waves generally result in less total erosion and a gentler beach slope. In some instances, reefs can actually repair the effects of previous erosion. This happens when sand washed in with the waves becomes trapped on the beach side of the reef.
Despite their benefit to the environment, reefs are inherently dangerous to naval travel. Historically, collisions with these underwater hazards have sunk numerous ships and caused damage to countless others. Often, this meant that areas with natural reefs were less accessible by ship and thus more defended against naval invasion. Logically, an artificial reef would provide the same protection, and many were built specifically for this reason.
