A Cry To People: The Case of Coral Reefs and Climate Change

Orlagh Turner - Writer

Over a series of articles, I will discuss the damaging effects humans are having on the environment through the continuation of our high maintenance lifestyle. If we carry on our beautiful and familiar planet will become an unrecognisable mess on which we can no longer survive.

Coral reefs are a major benefactor to the health of our oceans. They have a direct effect on the functioning of coastal ecosystems and have a serious impact on our future as a race. Despite Coral reefs only covering around 0.1% of our ocean floors, they support 25% of marine life. The arguably most famous reef being the Great Barrier Reef, which covers an astonishing 48,960 km2 of coastal floors. The small amount of coverage on our sea floors is only a fraction of what it once covered, and with the continuing exploitation of our marine ecosystems, this fraction will only become smaller and smaller, causing the reefs to decline at a frightening rate. Today’s article will focus on the effect climate change is having on the reefs, engaging in the impact we have on this wonderfully complex system and what is happening now to try to reduce the alarming rate of which our reefs are dying at.

What are Coral Reefs?

Corals like to live in shallow, warm water, so that they can photosynthesize. They have a symbiotic relationship with an algae called Zooxanthellae; these algae live in the polyps of the coral, giving the coral its wonderfully diverse colours, whilst also providing the coral with energy through photosynthesis. The polyps in return provide carbon dioxide and a home for the algae, showing the mutually beneficial relationship these organisms have. This relationship that the algae have with the polyps is effective but fragile; the Zooxanthellae are incredibly susceptible to change and the slightest change to their ecosystem can cause harm to these reefs, leaving them vulnerable to death. It is vitally important to understand exactly how these reefs work and how they respond to change in order to help them flourish in an ever increasingly damaging world. Thus, the common misconception that reefs are in fact plants is dangerous to the progression of improving living conditions for these microorganisms because people do not understand how these reefs work. Climate change is the biggest contributor to the decline of the reefs. With increasing temperatures, that cause a range of problems for the reefs, the reefs cannot cope in the conditions that they are subjected to and therefore die, which is not good for us if we want to continue living on this planet.

Climate Change:

The first and most direct problem for the reefs is the effects of climate change. The Earth is getting hotter and hotter, causing the living conditions for these algae to become less and less welcoming. Climate change forces sea temperatures and levels to rise, ocean acidification and increases the frequency of severe weather events, all of which affect the coral.

Rising Sea Temperatures:

As the earth is getting hotter, so is the temperature of the sea. Corals like to live in warm water but with sea temperatures becoming warmer, the corals cannot cope and therefore bleach. Coral bleaching is where the algae leave the polyps because they can no longer survive in their harsh environment, which consequently leaves the corals without colour or energy and therefore they die. Bleaching is occurring at a worrying rate with the annual maximum and minimum temperatures of the oceans, according to WWF, warming at 0.09-0.12oC per decade and are projected to increase by 1-4oC towards the end of the century, there is no clear future for corals. This is very scary considering that if temperatures increase by more than 2oC, most coral reefs will be eliminated. The sad reality of this though is that bleaching is not irreversible, if caught at an early enough stage and temperatures decline, the algae will return to the coral and flourish again- yet little is being done to resolve this. It requires around 10-15 years for newly developed coral to regain its little tenants, and longer, centuries even, for more mature coral to recover from bleaching. However, once dead the coral cannot rejuvenate. The Great Barrier Reef, one of the most prestigious reefs, experienced a mass bleaching between 2016 and 2017, leaving an astonishing approximant of 50% of its corals for dead according to IUCN. With no coral to provide housing for fish and more importantly food, the food web begins to diminish so that eventually larger fish such as sharks and even mammals like Dolphins struggle in the ever-tightening competition for food. These corals affect the ecosystem on a wider scale, bigger than what we could ever imagine and this directly affects us as a species too, which will be discussed later on.


‘The Great Barrier Reef is in grave danger. The twin perils brought by climate change- an increase in the temperature of the ocean and its acidity- threaten its very existence.’ -David Attenborough. Changes in the Ocean’s chemical make-up reduces the coral’s capacity to build skeletons, and therefore cannot create a habitat for other marine life. With more and more greenhouse gases being released into the atmosphere, the oceans are subjected to an abundance of CO2 that it is not prepared for. This damaging amount of CO2 depletes pH levels of the ocean, reducing coral growth and the structural integrity of the coral. This is because hard coral’s material is made up of calcium carbonate, which requires a certain pH level to extract calcium from the Ocean. Without the correct pH, these corals cannot extract calcium from the sea and therefore cannot build themselves, which is crucial if we ever want to recover the corals. Climate Interpreter claims that ‘some studies have shown a 52-73% decline in larval settlement on reefs that are experiencing lower pH levels. Therefore, considering that since the 18th century the Oceans have absorbed around 30% of additional CO2 that humans have ejected into the atmosphere, without these corals, this would still be in our atmosphere. If the decline in coral continues there is a prediction that by the end of this century all corals will become extinct, only existing in tales about ‘the old days’.

Severe Weather Conditions and Rising Sea Levels:

With a dangerous amount of greenhouse gases being emitted at a damaging rate every day, our ecosystem is becoming more and more overwhelmed, to the point that the occurrence of severe weather conditions is increasing, acting like warning shots for a bigger, more wide scale disaster. However, if the increased frequency of these severe weather events such as cyclones isn’t deterrent enough to emitting greenhouse gases, then the further damages these reefs experience from these weather events should be. The more intense the cyclone, the more damage to the coral, weakening its structure. Furthermore, the increased severity of weather conditions causes fresh water and increased amount of sediment to enter the coral’s habitat, which produces unbelievable conditions for the coral. The increase in sediment in the coral’s habitat is also blameable on the increase in sea levels. Higher sea levels introduce more sediment into the coral’s habitat, smothering it, reducing the coral’s light intake, making it harder for them to photosynthesis. On top of this, the higher the sea level, the less sun the plants can reach, the less they can produce food for themselves and die.

Why Is This All Bad?

Obviously aesthetically our oceans become less diverse and more deadly looking, reducing tourism and inhabitants.

It is a habitat for a range of diverse animals, without a home these fish are exposed to their predators. It supports around 25% of marine life despite only covering 1% of the Ocean’s floors.

Our oxygen comes from the sea- the algae photosynthesis providing oxygen for the earth – Michael Crosby a marine scientist told Business Insider that "Estimates are that up to 80% of the oxygen you are breathing in right now comes from the ocean. It doesn't come from the land. In order for you to continue to breathe, you have to have a healthy ocean."

Prevent flooding, coastal erosion and powerful waves- a 2014 study in Nature Magazine claimed that around 97% of wave energy was absorbed by reefs. With up to 200 milliuon people reaping the benefits of this. Without the reefs all wave energy would be directly impacted on land.

This article should have widened your eyes to the damaging effect we as a race are having on just the reef system alone and how the diminishing and depleting coral can have damaging effects on us in the long term; problems that are more irreversible than helping the conditions for coral reefs to get better.



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