10 Threats to the World’s Stunning Coral Reefs

Coral reefs: stunning, diverse, found worldwide, and incredibly fragile, despite the fact that they look like they’re made from stone. These delicate, beautiful structures are microcosms, communities filled with organisms living in a mutually beneficial world that provides food, shelter and protection from harsh weather. Sadly, 25% of coral reefs are already hopelessly damaged, according to the World Wildlife Fund, and many others face serious threats.

Combating damage to coral reefs requires understanding the multifaceted nature of the threats against their survival, and determining the best way to address these environmental issues before it’s too late. The loss of coral reefs would be tragic not just because we’d miss something beautiful in the world, but because they also play an important environmental role.

A coral reef viewed from above the surface of the water.

1. Ocean Acidification

Associated with climate change, ocean acidification occurs as atmospheric CO2 rises and the ocean absorbs it. The oceans have been burdened with a huge percentage of the rapidly-rising CO2 in the Earth’s atmosphere, and they aren’t equipped to handle it. Historically, the ocean’s pH was relatively stable. Today, it’s dropping due to reactions between seawater and CO2, and corals are missing out on valuable carbonate ions they need to form. Not only that, but as the level of dissolved CO2 in the ocean rises, it appears to be directly damaging coral skeletons, causing them to break and crumble.

2. Coral Bleaching

Thanks to climate change, the ocean is getting warmer. Corals, along with many other organisms in the sea, are extremely sensitive to small temperature changes. In their case, they can react to temperature increases by expelling their critical symbiotic algae, known as zooxanthellae. How critical? They provide up to 80% of the energy needed by the coral to survive, so when they leave, the coral is at risk of dying off — and it acquires a distinctive pale color, explaining the term “bleaching.”

3. Pollution

Coral, like the rest of us, doesn’t take kindly to toxins in its environment, and when exposed to chemical and industrial pollution, it can die. Moreover, corals are at risk of what is known as “nutrient pollution,” where the ocean becomes rich in nutrients as a result of fertilizer release, animal waste and related materials. It turns out there is such a thing as too much of a good thing — algae swarm in and bloom in response to the sudden food source, and they choke out the coral population. Better pollution controls and conservation are critical to prevent this issue.

A formation of cauliflower coral, surrounded by Hawaiian domino.

4. Overfishing

Coral reefs often furnish a number of valuable food species, but unfortunately, humans don’t always manage fisheries responsibly. Consequently, species can become fished out, disturbing the balance of the reef environment. Not only that, but some fishers use destructive practices like adding chemicals to the water to stun fish, deep water trawling or using explosives to quickly startle fish to the surface of the water. These practices damage the coral and harm bycatch — the “useless” species that won’t be harvested. Likewise, crab and lobster traps can damage reefs by banging around in the current and entangling coral and other species in their ropes.

5. Development

Coastlines tend to make popular places for development. Historically, they were ideal for trade and other activities thanks to their proximity to major ports. Now, coastlines have become one of the most popular places in the world to live thanks to existing settlement and stunning views of the water, along with activities associated with the ocean like surfing, going to the beach and snorkling. Unfortunately for coral, development is bad news, because it increases pressures on already fragile reefs. Some cities that once had thriving reefs now have nothing left, while in other rapidly-developing areas, things are not looking good for coral reefs.

Tourism, closely related to development, is also linked with damage to coral reefs. Tourists who aren’t aware of environmental issues may directly damage coral by stepping on it, harvesting souvenirs to take home, or disrupting the marine environment. Meanwhile, boaters may dump waste in reefs as well as damaging coral by hitting it with propellers and anchors.

6. Radiation

Ever get a sunburn? Coral has some natural protections against UV radiation, but it’s not prepared for ozone depletion. As the Earth’s ozone has become thinned in spots, some corals are showing signs of damage caused by UV exposure; it’s not exactly like they can slap on a layer of sunscreen for additional protection in the face of increasing exposure.  Like other changes in the Earth’s atmosphere, ozone depletion is hard to fix, and it’s difficult to come up with a way to protect corals from it.

7. Mining

Coral jewelry is just one of many things made from coral. In addition to being used in souvenirs for tourists, coral is also removed for use in making roads, paths and various other products. This is especially common in nations with limited sources of income, which turn to their reefs and other natural wonders to meet their economic needs. Even though this puts substantial pressure on the environment, and eventually depletes reefs, these nations may have no other choice.

A stunning coral formation with fish, in shades of moody purple and teal.

8. Sedimentation

Think back on the photos of coral reefs you’ve seen, or, if you’ve been lucky enough to see one in person, the real thing. One thing you’ll note in almost all of them is the extremely clear water. Coral hates suspended sediment, and doesn’t thrive in waters clogged with dirt, debris and other materials. Sadly, sedimentation is on the rise thanks to development and the destruction of wetlands, which normally act like giant traps for sediment, preventing it from reaching the ocean (and, incidentally, preventing loss of valuable topsoil). As sedimentation increases, coral populations suffer.

9. Stormy Waters Ahead

Tropical storms, hurricanes and other rough weather are a fact of nature, but evidence suggests they may be increasing in frequency and severity in response to climate change. Coral reefs can be badly damaged as a result of storm surge, the high, aggressive waves associated with severe storms. Sadly, this doesn’t just damage the coral; it also exposes the shoreline to further damage, because the coral would normally act as a buffer zone to help protect the shore.

Fish fluttering around a coral reef.

10. Rising Sea Levels

Coral is highly sensitive to light levels (one reason it can’t handle sedimentation and algae blooms). As sea levels rise, the amount of available light will decrease around existing reefs. Coral won’t be able to grow under those conditions, and it may begin to die off, which means that it will cease to support the reef and the larger population of organisms that relies on the coral for food and shelter. Formerly diverse areas could become deserts very quickly, and projections suggest that at current predicted rates of sea level rise, many famous coral reefs, such as those in the Caribbean, won’t be able to keep pace.

Photo credits: U.S. Fish & Wildlife Service, Anna Fox, USFWS - Pacific Region, U.S. Fish and Wildlife Service, and USFWS - Pacific Region.

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David V.
David V.2 years ago

All caused by humans.......

Carrie-Anne Brown

thanks for sharing :)

John G.
John G.2 years ago

When I've seen coral grow it doesn't seem to be reliant upon all that went on down the branch. So when they're cleaved off by storm or man's breaking it - why do the polyps die? Can't they go on building longer, thicker, or spread out to continue life/living? Are they like trees which need the roots to bring more nutrients? What is it they need from the polyps below that once broken off - they perish? If they have bacteria and chlorophyllic material they get sustenance from - why would breaking them make them die? I would think that no matter where they land - if not subverse from the sun they should be able to go on living and building more coral. I didn't think even the hollows of corals past made a difference to those higher up and vice-versa.

federico bortoletto

Grazie per l'articolo.

Eternal Gardener
Eternal Gardener2 years ago


Jan Sam
Jan Sam2 years ago

has everyone seen the coral reefs; i haven't ....though i dreamed of doing so as a child.

Trish Gascoigne

we must look after every living thing on this planet and anything we do is better than doing nothing at all....it is a beautiful planet lets keep it that way!!!

Sheila D.
GGmaSheila D.2 years ago

How sad. I have read this story several times and each time I've been left with nothing to say.

How sad. To lose the natural beauty of coral reefs. I do not swim, therefore I can only see the beauty second hand.

The World is losing so many beautiful things. For some reason this particular loss saddens me more, especially at a time we seem to be accumulating losses at an alarming rate.

How sad.

Paulett Simunich
Paulett Simunich2 years ago

Great article......Going to share with local scouts.....thank you!!!!!

Paulett Simunich
Paulett Simunich2 years ago

Great article......Going to share with local scouts.....thank you!!!!!