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The world’s disappearing underwater cities: coral reefs

By Clare Murphy 5 months ago

The surface of the ocean is a mysterious blue blanket. What lies beneath is hidden from our view. But what is hidden is incredible, and in danger.

Underneath the ever-changing surface of the ocean is what’s known as a large, blue desert. But now and then, in shallow seas, that blue blanket hides teeming cities – cities that are both different from and similar to our cities and towns around the world. These cities are coral reefs.

These underwater cities have the largest variety of life, besides rainforests. They form part of the “blue highway”, from our rivers to our oceans –  the road many species travel throughout their life cycles.

 

coral reefs

 

Just like our cities, they are noisy places. You can hear hawksbill turtles munching on sponges, the chorus of fish getting louder at sunrise and sunset, and snapping shrimp’s crackling sonic booms as they hunt.

Large fish like gropers and manta rays come into fish cleaning stations, much like we take our cars for a wash.

Grey reef sharks patrol the depths of reef drop-offs where the lights and colours of the coral city fade to a deep, vast blue of seeming nothingness.

Unfortunately, unlike our cities, which are mostly growing and expanding, coral reefs are disappearing or becoming bleached and weathered ghost towns.

As a result, the International Union for the Conservation of Nature (IUCN) ranks coral reefs as one of the most threatened ecosystems in the world.

 

coral bleaching

Original photo:  “Coral bleaching at Lizard Island March 2016” by The Ocean Agency/XL Catlin Seaview Survey/Richard Vevers is licensed under CC BY 2.0

Why are coral reefs disappearing?

Coral reefs are disappearing because of a mix of local pressures and a well-known global one – climate change.

Local pressures include overfishing, pollution, nutrient enrichment and coastal development.

Some of these local pressures are not dissimilar to some reasons why ghost towns are created.

Picher, a town in Oklahoma, is becoming deserted after the mining industry has left huge piles of rock containing toxic heavy metals lying around town. It is no longer safe for residents to live there.

Many coral reef fish have homes too – defined areas of the reef where they stay. Would you want to live in a wasteland? Fish will abandon sections of reef where corals have died off due to pollution.

These local pressures are small compared to the challenge that is climate change. It is the single biggest driver affecting our world’s coral reefs.

How is climate change affecting coral reefs?

Coral bleaching, increased intensity and frequency of large storm events, and ocean acidification are some of the ways climate change is affecting coral reefs.

Coral bleaching

coral bleaching

 

Every year, several of our major cities around the world are exposed to record-breaking heat waves because of climate change. It’s no different for coral reefs. They are hit by marine heatwaves. The effects are devastating and are known as coral bleaching.

Coral bleaching is when the tiny, colourful marine algae that live inside corals die. They die because the water becomes too warm for them.

Without these algae living inside them, the coral cannot get energy to grow and reproduce. They too then die and leave behind a white skeleton.

As shown in the documentary “Chasing Coral”, just before they die, some corals vividly fluoresce, like the night skyline of Las Vegas with its neon lights. It’s their last effort to save themselves.

The glowing pigments are a chemical sunscreen designed to protect the corals’ algal inhabitants from the sun’s intense rays. In this instance, it is triggered by the warmer waters. It is an eerily beautiful but sad site.

 

coral reefs

 

To give a sense of the scale of the problem, the World Heritage listed Great Barrier Reef is an iconic underwater megacity. It is so large it can be seen from space.

But over the last two decades, the reef has been hit by four major coral bleaching events. One in 1998, then 2002, then two back-to-back events in 2016 and 2017.

Because of these events, over 61 percent of the Great Barrier Reef has now been severely bleached at least once.

Coral bleaching isn’t restricted to Australian reefs. It’s happening worldwide. Research published in Science magazine has shown that the percentage of reefs being affected by bleaching per year has grown from eight percent in the 1980s to 31 percent in 2016. Can you imagine over a third of the world’s cities being hit by a major event each year?

Storm events

climate change

 

In 2005, the world’s eyes were on New Orleans as Hurricane Katrina devastated the city. Big storms like Katrina affect our coral reefs too.

For example, in 2016, tropical cyclone Winston caused widespread damage to Fiji’s reefs. Corals were broken or buried.

We can rebuild quickly after storms impact our cities. But for reefs, this isn’t true. Scientific studies show it can take between ten and 25 years for the reefs to recover.

Coral reef communities have coexisted with hurricanes and cyclones for thousands of years, but this balance is being shifted. Because of climate change these storms are becoming more frequent and intense leaving less time for corals to recover.  

 

coral bleaching

Ocean acidification

Our oceans take up and dissolve the increased amounts of carbon dioxide we release into our atmosphere. This is making our oceans more acidic.

Coral skeletons are made from calcium carbonate, which is eaten away by more acidic waters. With ocean acidification, it is possible that new coral growth will be limited and old corals will become weaker. This means our reefs will be more susceptible to the impacts of storms.

How do coral reefs sustain us?

Although coral reefs only cover one percent of the ocean floor, an estimated 25 percent of the world’s fish species spend parts of their lives in these underwater cities. The world’s general population, especially the many small coastal communities in developing nations, rely upon these fish for food.

Reefs protect those of us that live on the coast or islands from the worst of storm surges associated with cyclones.

 

 

Coral reefs also bring us joy and support tourism, as their beauty is astounding. There are the delicate branches of giant gorgonian fans, vivid arrays of colourful corals, flocks of large predatory fish like barracuda, and tiny neon-coloured fish the size of your thumbnail.

Not only that, but coral reefs are a modern day medicine cabinet. The plants and animals that live in these underwater cities are proving to be an excellent source for new medicines to treat cancer, arthritis, bacterial infections, Alzheimer’s disease, and heart disease.

Perhaps most importantly, healthy reefs mean a healthy ocean, and the ocean gives us the oxygen we need to breathe.

Michael Crosby, a marine scientist, recently told Business Insider that “Up to 80 percent of the oxygen you are breathing 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”.

Climate change affecting our world’s reefs is therefore an issue that concerns us all.

What can I do to help the world’s coral reefs?

ocean acidification

Original photo:  “Coral bleaching at Heron Island Feb 2016” by The Ocean Agency/XL Catlin Seaview Survey/Richard Vevers is licensed under CC BY 2.0

You may think because the biggest driver affecting coral reefs is climate change, that there is nothing you can do. This isn’t true.

You can live your life in a way that reduces both local pressures on reefs and your own carbon footprint.

If we address local pressures, coral reefs will be less stressed and more resilient. Imagine if you have challenge after challenge thrown at you. You become stressed and there comes a point where you may break down.

Our reefs are the same. If they are less stressed they will cope better with the challenges that come with climate change when they experience them.

The actions you can take are therefore many and varied.

 

 

For overfishing:

For pollution:

  • When you visit the beach “#Take3fortheSea”. Take at least three pieces of rubbish with you and put it in the bin.
  • Volunteer with local clean-up groups that pick up litter from land, river areas, and beaches. The litter in these areas ends up getting flushed into the sea.
  • If visiting a coral reef, protect yourself from the sun with a wetsuit, as sunscreen impacts the reef.

 

 coral reefs

 

For climate change:

  • Buy local produce so you buy food with fewer food miles.
  • Walk, ride or catch public transport to work.
  • Switch to 100% renewable energy providers.  

If you want to help coral reefs as well as experience them, you can volunteer on one of GVI’s coral reef focused marine conservation expeditions.

Most importantly, don’t let what is out of sight, beneath that ever-changing blue blanket, be out of mind.

Coral reefs, just like our cities, are complex and exciting places that are incredibly important not just for ocean life, but ultimately for ourselves.

If you want to make a difference for the world’s coral reefs, why not join one of our coral reef focused marine conservation expeditions? Head here to apply now.