Why corals bleach
Can coral survive a bleaching event? If the stress-caused bleaching is not severe, coral have been known to recover. If the algae loss is prolonged and the stress continues, coral eventually dies.
Coral reefs: home to 25% of all marine life
Yet some estimates put the total diversity of life found in, on, and around all coral reefs at up to 2 million species. All up, reefs are home to 25% of all marine life, and form the nurseries for about a quarter of the ocean's fish - including commercially important species that could end up on your dinner plate any night of the week.
This biodiversity translates directly into food security, income, and a multitude of other benefits to people. For example, although scientists have only just begun to understand how reefs can contribute to medicine, already coral reef organisms are being used in treatments for diseases like cancer and HIV.
For many coastal areas, coral reefs also provide an important barrier against the worst ravages of storms, hurricanes, and typhoons.
As thousands of communities across the world will tell you, coral reefs are essential not only to ocean health, but also to human health and well-being.
Where can I find coral reefs?
What are the main threats to coral reefs?
Coral reefs have survived tens of thousands of years of natural change, but many of them may not be able to survive the havoc wrought by humankind.Roughly one-quarter of coral reefs worldwide are already considered damaged beyond repair, with another two-thirds under serious threat.
Major threats to coral reefs and their habitats include:
- Climate change: Corals cannot survive if the water temperature is too high. Global warming has already led to increased levels of coral bleaching, and this is predicted to increase in frequency and severity in the coming decades. Such bleaching events may be the final nail in the coffin for already stressed coral reefs and reef ecosystems.
- Destructive fishing practices: These include cyanide fishing, blast or dynamite fishing, bottom trawling, and muro-ami (banging on the reef with sticks). Bottom-trawling is one of the greatest threats to cold-water coral reefs.
- Overfishing: This affects the ecological balance of coral reef communities, warping the food chain and causing effects far beyond the directly overfished population.
- Careless tourism: Careless boating, diving, snorkeling, and fishing happens around the world, with people touching reefs, stirring up sediment, collecting coral, and dropping anchors on reefs. Some tourist resorts and infrastructure have been built directly on top of reefs, and some resorts empty their sewage or other wastes directly into water surrounding coral reefs.
- Pollution: Urban and industrial waste, sewage, agrochemicals, and oil pollution are poisoning reefs. These toxins are dumped directly into the ocean or carried by river systems from sources upstream. Some pollutants, such as sewage and runoff from farming, increase the level of nitrogen in seawater, causing an overgrowth of algae, which 'smothers' reefs by cutting off their sunlight.
- Sedimentation: Erosion caused by construction (both along coasts and inland), mining, logging, and farming is leading to increased sediment in rivers. This ends up in the ocean, where it can 'smother' corals by depriving them of the light needed to survive. The destruction of mangrove forests, which normally trap large amounts of sediment, is exacerbating the problem.
- Coral mining: Live coral is removed from reefs for use as bricks, road-fill, or cement for new buildings. Corals are also sold as souvenirs to tourists and to exporters who don't know or don't care about the longer term damage done, and harvested for the live rock trade.
What WWF is doing
It has been exploring and protecting the Coral Triangle for some 20 years. It helps create policies to ensure responsible environmental management of the area, raise awareness, and promote the sharing of skills for better stewardship of the Coral Triangle's amazing marine world.
We work on major global policy issues facing reefs, particularly climate change, and also with communities, governments and partners around the world to reduce the threats to reefs including in the following regions: ocean.panda.org
How you can help
- Vote Earth by taking part in Earth Hour! As the biggest threat to coral reefs worldwide is climate change, we need to send a message to our leaders that warming must be limited to under 2 degrees Celsius.
- Spread the word! Click on the button to share this information with others via email or your favourite social networking service.