In addition to pressures from tourism, coral reefs are threatened by a large variety of factors.
- Global warming, through fossil fuel burning and deforestation, is increasing seawater temperatures. Coral reefs are extremely sensitive to small changes in temperature, and rises can result in corals expelling the algae that live within them. Algae give coral reefs their colour, so when the algae are expelled the coral appears white or “bleached”. Bleached corals usually die.
- Increased carbon dioxide levels in the atmosphere results in more CO2 dissolving in the oceans. This makes the oceans more acidic which in turn reduces the ability of corals to produce their limestone skeleton.
- Pollution is one of the major reasons for the decline in our coral reefs and the animals and plants which depend on them. Damaging pollutants include oil and gas, chemicals and fertilisers from agricultural runoff, human and animal waste products dumped in the ocean, all kinds of rubbish especially polythene bags and other plastic items which take decades to degrade, and discarded fishing gear.
- Coastal development has resulted in increased construction and boat traffic in inshore waters, which has had a devastating effect on many areas of fringing reef.
- Sediments deposited in the sea from rivers or coastal industry can smother coral reefs and prevent the essential sunlight from reaching them. This situation is made worse by the destruction of mangroves for firewood or to open up beach areas for tourism; mangroves act as a natural filter for sediments.
- Destructive and unsustainable fishing practices, especially cyanide and dynamite fishing which is still practiced in many developing countries, can be devastating for coral reefs.
- Coral mining is also widely practiced, in order to obtain limestone for use in concrete or for road fill, and to produce coral jewellery souvenirs which are widely available and popular in many tourist destinations.