Why Are Coral Reefs Dying? And What You Can Do to Help Save Them

Coral bleaching on the Great Barrier Reef during a mass bleaching event.

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Coral reefs are amazing underwater treasures, but more importantly, they're hugely critical for our environment and the health of our planet.

They provide a habitat for 25% of all known marine species, many of which also provide sustenance and livelihood opportunities to local populations. In addition to offering a diverse habitat, coral reefs sequester carbon from the environment and protect coastal communities from extreme climate events like storm surges.

Despite their crucial environmental role, since 1950 the world's oceans have lost 50% of their living coral reef coverage. And if swift action isn't taken to protect this precious natural resource, scientists estimate that all coral reefs could be dead by 2050.

Find out more about the reasons behind coral reef death and what you can do to help save them.

Why Are Coral Reefs Dying?

Coral reefs are under threat from many different activities, primarily human-based. We've looked at each of the main threats in more detail below.

Australia, Great Barrier Reef, heart shaped reef, aerial view

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Climate Change

Climate change can have many negative impacts on coral reef health, caused by a range of factors including:

  • Rising sea levels. This can lead to increased sedimentation and the smothering of coral reefs.
  • Increased sea surface temperatures. Higher temperatures place coral under stress, which leads to bleaching events and coral reef death.
  • Ocean acidification. As oceans around the world absorb excess carbon dioxide in the atmosphere, they become more acidic. This decreases the growth rate of coral and can affect their structure leading to more breakages.
  • Changes to ocean currents. This can affect the amount of food available to coral, as well as the dispersal of coral larvae.
  • Changes to storm patterns. Increased strength and frequency of storms in the areas around coral reefs can destroy these delicate structures.

Crown-of-Thorns Starfish

Crown of Thorns sea star (Acanthaster planci)
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Crown-of-thorns starfish are corallivores, meaning they eat live coral. In some areas, this species exhibits population explosions periodically and can cause rapid destruction to coral reefs as a result. In much of the Indo-West Pacific, these starfish are one of the main reasons for coral reef death.

The exact cause of these population explosions is still not fully understood. One theory is that it may be linked to higher nutrient levels from man-made pollution, which provides additional food for larval stage starfish. It's also thought that rising sea temperatures may promote population explosions.

Destructive Fishing Practices

Lost Fishing Net over Reef, Medeterranean Sea, Cap de Creus, Costa Brava, Spain

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Many different fishing methods have the potential to destroy coral reefs, including:

  • Blast fishing. Explosives detonated in the sea kill fish in the surrounding area, making them easier for fishermen to collect. This method also destroys coral reefs and other species not being targeted by the fishermen. Over time, it can also lead to the collapse of a fishery.
  • Overfishing, especially when a specific species is the target, can disrupt the delicate balance of a coral reef ecosystem. In some coral reefs, giant triton sea snails have been removed in huge numbers due to their attractive shell. As they are removed, the numbers of their natural prey, the crown-of-thorns starfish, explode, leading to further reef destruction.
  • Cyanide fishing. This method uses sodium cyanide to temporarily stun fish living on coral reefs. These fish are then collected and sold to both the aquarium and live fish food trade. The cyanide also kills the coral polyps. It's estimated that one square meter of coral reef is destroyed for each fish caught using cyanide.
  • Fishing gear. Bottom trawling and beach seine nets can destroy great stretches of deep-sea coral reefs as they roll over the seabed. Discarded fishing gear can also become attached to coral reefs and cause damage.

Pollution

Coral reefs can be negatively affected by a range of land-based pollution that then makes its way into the oceans:

  • Increased sediment levels. Coastal development, stormwater runoff, and agriculture can all affect sedimentation levels. When these sediments land on coral reefs, they can impact the coral's ability to feed, reproduce, and grow.
  • Increased nutrient levels. Fertilizer runoff can contribute to eutrophication and ocean dead zones, both of which can damage coral reefs.
  • Litter and microplastics. Land-based litter that makes its way into our oceans can get caught on coral and block the amount of available sunlight. Coral may also consume microplastics that are similar in size to the zooplankton they naturally feed on. Some corals have even been found to incorporate microplastics into their cell membranes.
  • Sunscreen. This either runs off with land-based water pollution or is introduced to a coral reef ecosystem as people swim over it. It's thought that 4,000 to 6,000 tons of sunscreen enter coral reef ecosystems across the world every year. Common ingredients in chemical sunscreens include oxybenzone and octinoxate, both of which can not only have a toxic effect on coral, but also have the potential to activate dormant coral viruses which then cause coral bleaching and death.

Effects of Coral Reef Destruction on the Environment

Coral reefs are known as biodiversity hotspots, and as they die, this affects the surrounding ecosystem. The death of half the world's coral since 1950 is also linked to a drop in reef biodiversity of 63%.

This has led to a decrease in the number of fish caught, despite an increased effort by the fishing industry. Worldwide, six million fishermen and women rely on coral reef fisheries, and this industry is valued at $6 billion. Fisheries that rely on coral reef biodiversity to provide a healthy quota of fish are at increasing risk as more coral reefs die.

Coral reefs that have been bleached or damaged are also less of a draw for tourism. Over time, this can impact the local economy.

Plastic spoon held in the hard coral. World ocean contaminated by plastic. Environment pollution concept.
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What Is Being Done to Protect Coral Reefs

Most coral reef experts agree that climate change is one of the largest threats to the health and biodiversity of these marine species. Businesses should be working towards setting and actively meeting emissions reduction targets and sustainable development goals (SDGs) in order to help coral reefs and our environment as a whole.

In some areas, like the Great Barrier Reef in Australia, crown-of-thorns starfish are removed from the reefs during a population explosion, in an attempt to limit their destructive effects.

Efforts are being made to reduce the impact of destructive fishing practices around coral reefs. Establishing marine protected areas (MPAs) can help prevent destructive fishing practices, but these need to be properly managed to ensure they're enforced effectively.

Cyanide fishing is illegal, but this is not easy to enforce. Researchers are developing tests to screen live fish for cyanide poisoning in order to discourage this practice. The potential of capturing fish at the larval stage—which doesn't harm coral reefs—has shown promise.

In terms of pollution, the Environmental Protection Agency (EPA) protects water quality in coastal zones and monitors the condition of reefs around the U.S. coastline. Activities like dredging are monitored so sediment cannot be discharged near reefs, and water quality standards are designed to protect coral reefs and the species that rely on their habitats.

In January 2021, Hawaii banned the sale of sunscreen containing oxybenzone and octinoxate as a way to try and protect its coral reefs. Sunscreen containing these harmful compounds is also banned in Palau, Bonaire, Aruba, some areas of Mexico, and the U.S. Virgin Islands. In some areas including Palau, other cosmetic and sunscreen ingredients like parabens and triclosan are also banned.

Coral reefs are one of the ocean's greatest treasures. Without action on both an individual and collective scale, these vitally important and biologically diverse organisms may be damaged beyond repair.

How Can You Help Save Coral Reefs

The dramatic decline of coral reefs can be upsetting, but there are plenty of individual actions we can take to try and save them, both at home and when visiting coral reefs.

  • When visiting coral reefs, use sunscreen containing zinc oxide or titanium oxide. These mineral ingredients are less likely to harm coral reefs. When in the water, try to use a rash vest as an alternative to sunscreen, and when on the water wear long-sleeved clothing and lightweight trousers.
  • Be careful when snorkeling or diving, to avoid touching reefs or damaging them with fishing equipment or anchors.
  • Reduce fertilizer use. Take care not to over-apply fertilizer and maintain a buffer along any waterways on your land.
  • Reducing stormwater runoff can help protect coral reef health by decreasing water pollution. Consider installing green infrastructure like a rainwater harvesting system, or adding a green roof to collect rainwater.
  • Live a low-impact lifestyle. Anything you do to reduce your impact on the environment, like choosing to switch to an electric vehicle, or recycling as much of your trash as possible, will have a positive impact on things like climate change and pollution, both of which negatively impact coral reefs.