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Why are our Coral Reefs at risk?


Coral reefs are one of the most important ecosystems on the planet. While they cover only .1% of the ocean floor, these rainforests of the sea are home to a quarter of all marine life. Thousands of species of fish, along with iconic octopi, sea turtles, sharks, and millions of other organisms,  depend upon coral reefs for their survival.


But what role do Coral Reefs play?


1 Coral reefs act as an essential food source, providing key nutrients and proteins for one billion people around the world, protecting coastlines from erosion, storm surges, and enhancing tourism economies.


2 Also, even marine life that do not feed on the coral directly, depend on it to sustain their prey, thus providing a fundamental part in supporting the ocean’s ecosystem.


However, coral reefs are currently facing a dire crisis. Recent studies have revealed that 50% of the world’s coral reefs have already been destroyed, and another 40% could be lost over the next 30 years.

So why is this happening and how can we stop it?

Global Warming/Heating Impact on Coral Reefs

One of the biggest reasons for the decline of coral reefs is coral bleaching as a result of global warming. Coral bleaching occurs when heat stress causes the coral to release its brightly coloured algae, leaving it completely white. If the bleaching event lasts for more than a couple of weeks, the corals will starve to death. Once this happens, the coral is effectively dead and can no longer provide a habitat for the surrounding marine life.


The global extent of coral bleaching from 2015-2016. Each circle represents one of 100 reefs, with red indicating severe bleaching, yellow indicating moderate bleaching and blue showing no bleaching. Source: Hughes et al. (2017)


Scientists have been studying coral reefs for over a century, examining the link between heat exposure and coral bleaching. The first recorded bleaching occurred in 1911 on Bird Key Reef in the Florida Keys during a period of hot weather, which caused 5-10% of the reef lost. Since 1911, there have been several more mass bleaching’s, with one of the worst occurring in 1997-98. During these 24 months, around 16% of the world’s coral reefs were destroyed with scientists warning that half of those may have been lost forever. In 2016, a nine-month marine heatwave caused the largest bleaching in record history, destroying over 30% of Australia’s Great Barrier Reef.

Research carried out, confirmed the link between heat exposure and bleaching with the investigation revealing reef areas which suffered the most severe damage were where heat exposure was most extreme. The northern third of the reef was the most severely affected, with the study discovering that of the 3,863 mini-reefs that make up the Great Barrier Reef; 29% lost two-thirds or more of their corals. Bleaching is likely to become increasingly more common as sea temperatures rise, with scientists warning that a large proportion of coral would not survive if temperatures raised by a further Two Degrees Celsius.


Sea level rise, caused by global warming, is another issue which could result in severe consequences for coral reefs, as they depend upon shallow waters to survive. Over the years, coral reefs have demonstrated their ability to build themselves upwards, layer upon layer, to keep up with natural sea level rise. However, researchers fear that the loss of coral in recent years means the reefs will be unable to grow fast enough to keep up with the predicted sea level rise.


This could impact the coral reefs ability to reduce wave energy and regulate water circulation, leaving the reefs vulnerable to wave destruction.



A recent study conducted by a research team in the Atlantic and Indian Oceans measured the growth rate of 200 coral reefs, then compared the rate of growth after a 2.6 degrees Celsius rise in atmospheric temperature. The results revealed that only 3-6% of coral reefs studied in the Indian and Atlantic oceans would be able to compensate for projected sea-level rise, while the remaining reefs studied would experience a rise in the water depth of more than 0.5m, exacerbating the destructive impact of waves on reef areas.



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Coral Reef Facts & Figures


Of all known marine species call it home.

100, 000 to 30,000,000

Years for a barrier reef to reach full maturity.


Of all coral in the world has died since 2015.

Tourism a threat to coral reefs


The sheer breath-taking beauty and magnificence of the ocean’s coral reefs have naturally led to a large surge of tourism in these areas, creating a thriving and immensely profitable industry for many countries across the globe. Studies show that on average, countries with coral reef industries derive more than half of their gross national profit from them.

However, this has come at a high price, as tourism and coastal development are, ironically, accountable for much of the destruction and depletion of the reefs around the world.


The National Oceanographic and Atmospheric Administration (NOAA) identified the threat of tourism and recreational activity as medium or high in nine of fourteen locations.


Irresponsible business operations have certainly played a large role in afflicting damage, while the carelessness of tourists is also a large contributing factor. Many tourists are simply unaware of the damage they cause. Standing on the coral or even touching it, causes the coral organisms to fight off the pollutants, which can cause coral bleaching.


The natural growth rate is around 0.3 to 2 centimetres per year for larger corals, and up to 10 centimetres per year for branching corals. Depending on their size, it can take barrier reefs 100,000 to 30,000,000 years to reach full maturity. Yet once faced with human contact, the coral can die within just a matter of months.

“The twin perils brought by climate change, an increase in the temperature of the ocean and its acidity, if they continue to rise at the present rate the reefs will be gone within decades and that would be a global catastrophe.”

Sir. David Attenborough, Natural Historian and British Broadcaster

Coastal Development and its Impact on Coral Reefs


A large increase in tourism has created a demand for development, however, development in coastal areas have had serious knock-on effects for the coral reefs. Construction close to the shoreline causes sediment to enter the sea, which covers the coral reefs, blocking out sunlight required for photosynthesis, and depriving them of key nutrients.


This can also make the reefs inhospitable for marine life, as fish and other marine life are unable to feed off the corals. Damage from sediment has been observed across many coral reefs in developing areas. In 1994 the Bahía Culebra reef in Costa Rica suffered mass destruction after the reef was severely burned due to leftover sediment from the construction of a tourist centre. This resulted in 80% of the reef being completely destroyed.


Coastal development has also led to water pollution from chemical fertilizers, and human and agricultural waste disposable. This causes changes to the chemical makeup of the water which can cause damage to the coral, and in many cases will kill the coral completely.

Unsustainable Over-Fishing


Another explanation for coral reef decline is the rise of unsustainable fishing practices. Chemicals like cyanide and dynamite are often used by fishermen to stun the fish, making them easier to catch. However, these chemicals have proven to be highly destructive for the coral reefs, causing them to break apart and die. Unfortunately, it’s not just the fish sought after by the fishermen that are affected by the chemicals either, and many other marine species die as a result of their actions.


Overfishing is also a problem which is having adverse effects on the ecological balance and biodiversity of the reefs, as a significant drop in even one or two species can have a negative, ripple effect on the food chain. For example, overfishing for herbivorous fish can result in increased algal growth, which can be harmful, and sometimes even deadly for certain species due to the toxins they produce.


The Risks Coral Reefs Face

Reef building corals threatened by rising sea temperatures
World heritage sites will be destroyed by 2100 from greenhouse gases if emissions are not changed
Tonnes of sunscreen deposited by coral reef tourists per year
Coral reefs will disappear by 2030 if the human impact is not changed
Coral reefs globally threatened by Coastal Development
Warm water coral reefs damaged by sedimentation

What is the solution?


In order to save the ocean’s coral reefs, rapid action is needed.


Coral reef decline is happening at twice the pace of rainforest decline, and scientists have warned that over the next 10-40 years another 35% could be lost unless significant action is taken. A report released in November 2018 by the US National Academies of Sciences, Engineering, and Medicine (NAS) stated that “Human intervention is needed to ensure the persistence of the world’s coral reefs”.


One solution, which has already proved to be successful on a small scale, is the process of coral farming. The process involves collecting coral from the reefs and growing it in a nursery until it has fully matured, before returning it to the ocean at restoration sites.


Coral farming has been used for several decades for small scale research and through community projects, the process has proved to be hugely successful in restoring the damaged reefs. The success has led to local and federal governments now providing funding and support for coral farms projects around the world.


While most coral nurseries used for coral farming are ocean-based, Coral Vita has started growing coral using land-based nurseries. By using a laboratory process referred to as ‘Microfragmenting’, coral growth can be achieved at 50 times the natural rate. This has enabled the restoration of certain coral species, such as Great Star corals, which would otherwise grow too slowly to be feasible for restoration using ocean-based nurseries.

What else is being done?




In the Philippines, there are a number of government and NGO initiatives to introduce coral farming techniques to the local fisherfolk.


One example is a program run by the University of San Carlos in Cebu, which aims to construct three coral fishery units (CFU), consisting of small local in-situ coral farms tended by villagers. These CFUs hope to provide up to 30,000 coral fragments per year to restore local reefs.


Combined with ecotourism, the goal of the project is to help the local fisherfolk to understand the importance of protecting the reefs and educate them around the ecotourism benefits of reef restoration and coral farms.


Currently, there are 186 CFU in operation and more than 15,000 fragments have already been produced, helping to successfully restore parts of the reef. Additionally, the number of fish species in CFU areas have also increased, providing a food source for the local villages too.


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In Australia, another restoration program has been set up, in an attempt to help restore the Great Barrier Reef, following the mass bleaching in 2016. David Suggett, a marine biologist leading the Future Reefs Program out of the University of Technology Sydney, worked with a team of researchers and a local reef-tour company, to collect 12 species of coral that had survived the bleaching, and grow them on mesh platforms in a sandy lagoon.


After growing the coral for several months, the coral fragments were planted back onto the reef, in the hope that it would speed up the recovery process, and when the next heatwave strikes, there will be a greater chance of the coral surviving.



Additionally, in Maya Bay, Thailand, tourist bans have been introduced in an effort to help coral reef recovery. In the past decade, Maya Bay has become a hugely popular tourist destination after making an appearance in the famous Leonardo DiCaprio film, The Beach.

In 2008, there were around 170 people per day visiting the location, however in recent years that number has increased to around 5000, resulting in over 80% of the coral reef being destroyed. In 2017, authorities announced that the beach would be closed to tourists for two years to allow the reef a chance to recover.


However, by 2018, very little progress had been made and authorities made the decision to close the beach indefinitely until the ecosystem “fully recovers to a normal situation”.


Much of the action taken towards helping restore the coral reefs is still in the early stages of development. At the moment, it is too soon to measure the long-term success of these actions. However, there is hope that human intervention will enable coral reefs globally to recover and thrive again with careful conservation helping preserve the unspoilt coral reef that remains.

List of Coral Reef Protection Charities

Who else is taking action?

How can you help out?


Like our Plastic Pollution guide, once we are made aware of the consequences of our actions, we have an opportunity to change our habits for the better and reduce our impact on the ocean.


Here are 4 things you can do to help make a difference:


•   Share this guide on social media – whether it’s a quick tweet, an Instagram story, or a Facebook post – everything helps!

• Take precautions when in the ocean- check sunscreen ingredients to make sure there are no chemicals that harm marine life, if you dive, don’t touch, and practice safe boating by anchoring away from the coral reefs.

•   Donate & Volunteer – we have listed some charities above who are working hard to preserve our reefs. Also, you can help out in local beach or reef cleanups, and if you don’t live near the coast, look at how you protect your own watershed.

•  #PostSurfBeachClean – take park in our post-surf plastic pickup. Take a walk, pick up some plastic,  take a snap or video, and share. Be sure to use the hashtag #PostSurfBeachClean and tag @slo.active on Instagram (or see other social icons below). This will stop potential sedimentation getting into the coral. More info here


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This guide was written by SLO active with the input from Coral Vita.




Delbeek, J. Aquarium Sciences and Conservation(2001)

Earthjustice. Coral Reefs and the Unintended Impact of Tourism. (2016)

Ellis-Petersen, H. Thailand bay made famous by The Beach closed indefinitely. The Guardian. (2018)

envirobites. Are Harmful Algal Blooms a New Concern For Coral Reefs?. (2018)

Ezzat, L. Coral reef growth affected by sea level rise – Coral Guardian. Coral Guardian. (2018)

Globalissues.org.  Coral Reefs — Global Issues. (2013)

Halpern, Gator. Coral Vita

Icriforum.org. Status of and Threat to Coral Reefs | International Coral Reef Initiative.

Interamerican Association for Environmental Defense (AIDA). Coral Reefs and the Unintended Impacts of Tourism. (2016)

Nationalgeographic.com. Can new science save dying coral reefs?. (2018)

Nature.com. What risks do Tourists Pose to Coral Reefs? Are We Loving the Reefs to Death? | Saltwater Science | Learn Science at Scitable. (2013)

SECORE International, Coral Reefs are dying

The World Counts. Percent of coral reefs left – globally, right now.

UN Environment. Building the world’s first land-based coral farm. (2019)

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