Coral reefs can be used as building materials and to produce lime, mortar and cement (Dulvy et al., 1995). 20,000m3 of coral reefs are mined every year in the Maldives as they are the main construction material used in that area (Cesar, 1996). In some areas, coral structures are crushed and used as fertiliser (Kühlmann, 1988).
These are very destructive processes, however the most damaging process is possibly caused by the petroleum industry. Large amounts of oil and gas can be found below living reef structures and it is thought that very old reefs such as those found in areas in the USA, Canada and Siberia, have large amounts of oil in the limestone of the reef (Hodgson, 1997). Due to the value of oil, more and more research is being done to find reefs with large amounts of oil in their structure (Kühlmann, 1988).
The exploitation of reefs for oil is definitely not sustainable and may reduce the ability of the reef to serve its other uses, which is why it is possibly the most destructive mining process. Figure 13 shows an image of a dead coral reef structure.
Furthermore, this destructive process can reduce coral abundance and diversity (Shepherd et al., 1991). A study by Brown and Dunne (1988) found that the percentage cover of un-mined reefs was between 11-60% and on mined reefs it was less than 5%, showing a reduction in abundance of mined reefs. In addition, diversity was also reduced as mining results in a loss of live coral which reduces the fish abundance and diversity and also the topographic diversity. This results in a decreased species diversity of reef fish communities (Shepherd et al., 1991).
Recovery of a coral reef after mining is slow. This is because a rubble-covered surface is left and any coral that settles will be carried away in strong water movements, leading to poor recruitment (Shepherd et al., 1991). Therefore, the recovery of coral reefs after mining is extremely slow and may never recover back to their original state.