Coral bleaching

Gorgeous, delicate coral reefs are home to millions of fish and fundamental to our own survival. Coral bleaching is a global crisis, caused by increased ocean temperatures caused by carbon pollution. Climate change is the biggest threat to our Great Barrier Reef. The Reef needs our help while there’s still time.

Coral reefs are not just beautiful, brightly coloured backgrounds for serene snorkelling experiences — they are vital to life on earth. At least a quarter of the world’s marine life needs coral reefs for some part of their life cycle. Despite their beauty and importance coral reefs around the world are disappearing fast. Water pollution, overfishing and coastal development are taking their toll on coral reefs at the local level, while carbon pollution threatens reefs worldwide and remains their biggest threat.

Carbon pollution is warming our oceans and causing corals around the world to bleach. It has already led to increased levels of coral bleaching around the world, which are predicted to increase in frequency and severity in the coming decades. The mining and burning of coal releases carbon pollution into the air, which is heating our planet and warming our oceans. If we continue to pollute the air and the ocean with carbon emissions at our high rate, coral reefs around the world will face a catastrophic future in coming decades – in our lifetime.

What is coral bleaching?

The stunning colours in corals come from a marine algae called zooxanthellae, which live inside their tissues. This algae provides the corals with an easy food supply thanks to photosynthesis, which gives the corals energy, allowing them to grow and reproduce.

When corals get stressed, from things such as heat or pollution, they react by expelling this algae, leaving a ghostly, transparent skeleton behind. This is known as ‘coral bleaching’. Some corals can feed themselves, but without the zooxanthellae most corals starve.

Can coral recover from bleaching?

In some instances corals can recover from bleaching. If conditions return to normal, and stay that way corals can regain their algae, return to their bright colours and survive. However prolonged warmer temperatures and other stressors, like poor water quality, can leave the living coral in a weakened state. It can struggle to regrow, reproduce and resist disease – so is very vulnerable to coral diseases and mortality.

It can take decades for coral reefs to fully recover from a bleaching event, so it is vital that these events do not occur frequently.  If we continue burning fossil fuels at our current rate then severe bleaching events are likely to hit reefs annually by the middle of the century. This would be devastating for coral reefs as they would have no chance to recover.

We need to urgently reduce our carbon pollution and limit global temperature increases, or the world’s reefs will face a bleak future.

How is our Great Barrier Reef affected?

Carbon pollution is causing unprecedented damage to our Great Barrier Reef. In recent years, our Reef has suffered severe mass coral bleaching, faster and more severe than scientists predicted. If we don’t act to halt this pollution, we risk the future of our precious Reef.

Over 2016 and 2017, our Reef suffered back-to-back bleaching, leaving half of the shallow water corals dead. Results from extensive aerial and underwater surveys showed that 29% of corals died from the 2016 event alone – with most perishing in the northern section, where waters are warmest.

Source: Great Barrier Reef Marine Park Authority

2017’s bleaching event reached further south from Port Douglas to Townsville. A further estimated 20% of corals died. To compound this, a category four cyclone ravaged the Whitsundays region – decimating coral reefs in its path.

A combination of two severe bleaching events, Cyclone Debbie and current outbreaks of coral-eating Crown of Thorns starfish have significantly impacted the health our Great Barrier Reef.

We can solve the coral bleaching crisis – if we choose to

Human beings are incredible when we act together. With real leadership we can stop runaway carbon pollution and allow our coral reefs to recover and rebuild. But to do this, we must quit dirty coal, and transition to renewable energy today. If we take climate leadership then our coral reefs, and the thousands of species that rely on them, can rebuild and thrive for generations to come.

Our oceans have no borders. This is a global crisis, but change starts here.

If we lose coral reefs we also lose a vast number of fish and other animals that rely on them. This will have terrible consequences right up the food chain impacting larger creatures, like dolphins and sharks that rely on reef fish for their diet. Coral bleaching risks not just our oceans and wildlife, but the livelihood and food security of over half a billion people worldwide.

We have the power to change the future for our Great Barrier Reef.  

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