Part 3 looks at the existing and emerging threats to corals reefs as a result of non-climatic anthropogenic factors. Here I review Mulhall (2007) SAVING THE RAINFORESTS OF THE SEA: AN ANALYSIS OF INTERNATIONAL EFFORTs TO CONSERVE CORAL REEFS (PART III A).
The world’s coral reefs are on a downward trajectory. A study in 2004 estimated that since the 1950’s twenty percent of all reefs worldwide had been destroyed, with no chance of recovery, and an additional twenty-four percent of reefs were under imminent threat of collapse. These worldwide declines are a result of numerous causes; they can be global threats (part 1 & 2) whilst others are localised to specific countries and regions (like those discussed below).
Overfishing: Overfishing is a worldwide problem, having wiped out a third of the world’ s fish stocks. Fishermen are catching smaller fish species which are lower down the food chain, not only to make a living but for a rich source of protein and to ensure they and their families survive. Coral reefs are known for the biodiversity and abundant fish numbers, however over fishing here has many problems. It not only causes harm to the humans who depend on them for food but also harms the coral reefs where these fish once lived. Coral reefs have a complex relationship with the fish that live within them. Reefs provide security and habitat for many species of fish and in return herbivorous fish control the abundant algae found in reef environments. Without adequate number of plant-eating fish a reef can become overwhelmed by algae.
Destructive Fishing: there are two types of fishing practices which not only deplete fish stocks but also damage the reefs themselves:
Blast fishing- involves the use of dynamite to stun and kill the fish which then float to the surface. This method almost certainly guarantees the fisherman a large catch BUT the dynamite kills all marine life in the area including sensitive corals and leaves nothing to replenish fish stocks with.
The use of cyanide : cyanide is poured into the water around the reefs, stunning tropical fish and allowing for their capture, albeit for the ornamental aquarium fish market or for food. Despite being outlawed in many countries, one million kilograms of cyanide has been illegally used for fishing in the Philippines since the early 1960s. As with blast fishing, cyanide has a devastating impact on surrounding corals and other marine life.
Pollution: because coral reefs only live in warm environments with abundant sunlight, they are found in shallow waters along the coastline. Unfortunately for coral reefs 40% of the world population also live along these coast lines. Approximately 80% of all marine pollution now comes from land-based activities, including agricultural, municipal and industrial runoff, agricultural wastes, and atmospheric deposition. Coral reefs’ close proximity to land renders them especially vulnerable to this land based pollution. Agricultural and industrial runoff carries herbicides and other chemicals that harm corals, in addition to excess nutrients that create algae and phytoplankton blooms that suffocate corals. Other types of land-based pollution, such as sewage, wreak havoc on coral reefs as well. In Indonesia, a country located at the centre of the greatest known land and marine biodiversity on the planet, massive migration of the population from rural areas to coastal cities is taking its toll on the country’s reefs. Of all the pollution washing off the land and into the reef systems, untreated sewage is likely the worst. In Jakarta, the capital city, enough untreated sewage is released directly into the bay “to fill seventy-five Olympic-sized swimming pools, each day.” By 1993, one biologist had noted that all the coral reefs in Jakarta Bay were “functionally dead”.
Tourism: When done in the wrong way, tourism associated with coral reefs threatens the very reefs on which the industry depends. The global economics of reef based tourism are huge, (just under 10 billion dollars a year); Australia’s Great Barrier Reef supports a $4.2 billion tourism industries alone, with nearly two million tourists each year.
Irresponsible tourism threatens reefs in a variety of ways: from careless swimmers and divers, to improperly placed boat anchors, to discharges of sewage and other water waste from hotel and resorts. The cruise ship industry is of particular concern for reefs, given the sheer magnitude of the business. Cruise ships regularly “disgorge” throngs of passengers onto coastal reef areas, with around two thousand cruise ship passengers diving in Cozumel, Mexico’s reefs, in any given day.
Mining: in East Africa Southeast Asia and the Pacific Ocean coral reefs are mined for their large quantities of limestone (calcium carbonate). This limestone can be mixed with sand and water to create cement and be used in the building industry. Alternatively it is used in the pharmaceutical industry to make pills and more recently researchers have mined corals for bone graft clinical trials. Often the corals are mined simply for piece of dead and living coral which can be used in home as decorations and in jewellery worldwide.
Invasive Species that are discharged into reef areas from the ballast of ships also pose a threat, especially when no predators or parasites for these introduced species exist in the host reef environment. One of the most noticeably damaging invasive species is the crown-of-thorns starfish of the Great Barrier Reef. This is a voracious coral polyp eater and is increasingly damaging reefs. Declines in predators of this spiny toxic starfish, due to over fishing and pollution have led to population explosions which is currently destroying huge areas of the coral reef.
Other Threats: In addition to those described above coral reefs are threatened by an array of challenges. These include SEDIMENTATION associated with coastal development and deforestation, DREDGING of reefs to create deep water channels and marinas and coral DISEASE. The occurrence of coral disease has increased dramatically in the past ten years, a likely combination of the threats discussed above and in parts 1&2.
