Coral reefs are degraded by an accumulation of stress from human activities. Overfishing, pollution and coastal development are high on the list of factors in chronic stress. Some coral reefs are covered with sand and sediments. Others are dredged or blasted for their limestone or to improve access and safety of navigation. In addition to this, the overall long-term changes (higher sea temperatures and CO2 levels), storms, earthquakes and volcanic eruptions also affect coral reefs.
Increasing demand for fish has led to the overfishing of reef species. Overfishing of certain species can easily affect the ecological balance and biodiversity of the reef. For example, overfishing of herbivorous fish can lead to high levels of algal growth that can quickly suffocate corals.
Dynamite fishing and cyanide make the fish easier to catch. These practices do not target species, they destroy everything where they are applied. Damage on the coral reef affects the entire reef ecosystem, and thus has an immediate impact on the livelihood of fishermen and their families in these areas.
Tourism generates large amounts of money for the host country. Unregulated tourism can cause damage to the surrounding environment because of negligent divers, misplaced boat anchors and hotels discharging untreated wastewater (polluting water, creating sedimentation, whilst also encouraging the growth of algae that disturb corals).
Coral reefs need water that is low in minerals to develop. Pollution from land-based human activities, when transported by river flows into coastal waters can damage coral reefs.
It is estimated that nearly 2 million people worldwide have an aquarium. The vast majority of aquariums are constituted of species caught in the wild. The threats brought about by this trade include the use of cyanide for the collection of fish, overly targeted organisms and high levels of mortality due to different maintenance and shipping practices.
Coral bleaching occurs when the symbiosis between corals and their symbiotic zooxanthellae (algae) stops, resulting in the loss of these microalgae and the rapid bleaching of the coral host (hence the term “bleaching”). This is a stress response from the coral host which can be caused by various factors. The most common and most serious cases are caused by an increase of the surface’s temperature.
If the ocean surface temperatures continue to rise, the frequency and severity of coral bleaching will also increase, possibly affecting the ability of coral reefs, as we have known them, to adapt and provide most services we ask them.
This is the name given to the decreasing pH of ocean water caused by the absorption of carbon dioxide from the atmosphere. Although the natural absorption of CO2 by the world’s oceans helps mitigate the climatic effects of CO2 emissions, the resulting decrease in pH (i.e. making water acid) will have negative consequences, especially for oceanic calcifying organisms such as coral reefs.
Observations since 1961 show that the average temperature of the ocean on a global scale has increased, even at depths of 3000 m (IPCC report), and that the ocean has absorbed more than 80% of the increase in heat. This temperature increase causes rising sea levels and creates problems for low-lying countries.
Over the past 10 years, the incidence of diseases developed in corals appear to have increased dramatically, contributing to the deterioration of coral reef communities worldwide.
Species that have been moved intentionally or not, due to human activity, in areas where they do not coexist naturally are called “invasive species”. Often natural controls such as predators and parasites of invasive species are lacking. These invasive species can therefore multiply and change rapidly. The damage caused by these species can be devastating: altered ecosystem dynamics, biodiversity loss, reduced resilience of ecosystems and loss of resources.
A Coastal Protection Reefs occupy less than 0.2% of the seabed. Yet they run along more than 150 000 km of coastline in more than 100 countries and territories. By their massive formation between the surface and the first few tens of meters deep, coral reefs are a very effective for absorbing elements coming from the ocean. They absorb waves energy and contribute to environmental protection through the reduction of coastal erosion. They reduce the damage in case of storms, hurricanes, and in some way, the energy of tsunamis. In doing so, they protect both ecosystems located between the reefs and coasts, such as seagrass and lagoon for example, and human settlements located by the sea. Their impact is so effective that the man mimics immersing concrete structures along some of our fragile coasts. Without this protective role, some countries in atolls, such as the Maldives, Kiribati, Tuvalu and the Marshall Islands are literally built on coral reefs and would not exist and without the protective fringe.
In these labyrinths of living limestone scientists estimate that over one million plant and animal species are involved and they hostreceive more than 25% of all species of marine life. It is one of the most important biodiversity hotspot on earth. Coral reefs often host juvenile fish that live further offshore. They are the basis for the formation of other ecosystems. Indeed, the food of coral formations by the hordes of parrotfish led to the formation of very large tracts of sand and by the action of currents, leads to the formation of shoals, islands and especially in areas prone to the formation of mangroves and other coastal forests. Mangroves are also one of the most sought after by some species of fish to come and lay their breeding juvenile ecosystems. The surface of coral reefs in the Indo-Pacific may also be the place of habitat of human cultures that have lived there for centuries. These people can literally live on the immersed surface reefs, cultivate these soils, build their dwell from coral blocks, and even build artificial islands where families can settle. They represent both a World Natural Heritage by the age of reefs but also a human World Heritage because of the existence of these cultures. They are our heritage and to pass on to the generations to come.
More than 275 million people live within 10 kilometers of coastline and within 30 kilometers of coral. One eighth of the world’s population, approximately 850 million people live within 100 kilometers of coral and are likely to reap the benefits of ecosystem services provided by coral reefs. A large proportion of the human population live in developing countries and island nations and therefore depend to a large proportion of food taken directly from the reef waters. It is vital to preserve it from environmental pollution. Reef animals are an important source of protein, contributing about a quarter of the fish catch average in these countries. “Well managed” reef can provide between 5 and 15 tons of fish, crustaceans, molluscs and other invertebrates per square kilometer.
Because of the income coming directly from fishing in their waters, reefs provide resources and services worth billions of dollars every year. Millions of people around the world depend on coral reefs for food, protection and employment. These figures are even more impressive than the reefs cover less than one percent of the earth’s surface. According to one estimate, the total annual earnings of coral reefs in the world is $29, 8 billion. Tourism and leisure activities represent $9.6 billion, coastal protection $9 billion, fisheries $5.7 billion and biodiversity $ 5.5 billion (Cesar, Burke and Pet-Soede, 2003). Economically, the total value of Philippine reefs alone is estimated at 1.1 billion dollars per year.
The reefs are often essential element in the economy of tropical regions they inhabit. They attract divers in effect, freedivers, recreational fishermen and lovers of white sand beaches. More than 100 countries benefit from tourism related to reefs and it contributes more than 30 percent of export earnings in more than 20 countries. Local economies benefit from billions of dollars from visitors to reefs with their companies exploiting reef ecosystems. Through tourist services, billions of dollars are collected. In many small islands, more than 90 percent of new economic development is dependent on the coastal tourism. The reef tourism, if managed in a sustainable manner that is respectful of reefs by limiting the destruction and pollution caused by that tourism, particularly in overemphasis may provide alternative or additional resources of income for poor coastal communities in developing countries.
Coral reefs also contribute to the advancement of research. Being deprived in a great measure of all possible movements, corals have developed a very effective arsenal of chemical weapons to defend themselves and to make war in the conquest of the reef area. Their weapons are so effective that it has a wide distribution area and therefore a greater number of potentially hostile species. Many of these chemical compounds have molecules that have the potential of our drug discovery. Reef organisms are used in the treatment of diseases such as certain cancers including leukemia, HIV, cardiovascular diseases, ulcers. In addition, long coral skeleton, because of its very close similarity to our bones nature, served as material for bone grafts. Scientists, for example, synthesized an effective anticancer agent against tumors, especially those of the ovaries, in the Caribbean species of sea squirts. Because only an infinitesimal part of the reef organisms were sampled, analyzed and tested, the potential for new drug discovery is simply enormous.