Coral Reef Awareness Week, in the third week of July each year, was created to highlight the importance of coral reefs and the need to protect them. Coral reefs only cover 0.2 percent of the ocean floor, but these amazing ecosystems support around 2 million species of marine plants and animals. In addition, more than 500 million peoplethroughout the world rely on coral reefs for food and income.
Coral reefs have been on the earth for about 500 million years. But in the past few decades, coral reefs have been dying at an alarming rate. It’s estimated that 19 percent of the world’s coral reefs are already dead, and 60 percent are currently at risk. If global action is not taken to stop this decline, all coral reefs will be in danger by 2050.
You may have heard about how sunscreen can be toxic to coral reefs, but many other factors also impact the health of coral reefs. Let’s look at some of the worst threats coral reefs currently face.
1. CLIMATE CHANGE
Research suggests that climate change is quickly becoming the most significant threat to coral reefs today.
A coral reef is actually a community of hundreds to thousands of corals, which are small, delicate animals that are easily disrupted by changes in their environment. Each tiny, soft-bodied coral secretes a hard outer skeleton of limestone to keep itself safe. The accumulation of these skeletons creates a coral reef.
This process has been going on uninterrupted for thousands of years and has created the massive coral structures we know today. But corals also form an incredible partnership with a type of algae known as zooxanthellae to keep this cycle going. Zooxanthellae are single-celled algae that can live within the corals’ soft tissues, where they photosynthesize in a way similar to plants. The corals can then feed off the products of the algae’s photosynthesis and continue to grow and thrive.
It’s been observed that a rise in ocean temperatures of only one or two degrees can disrupt this unique partnership. When oceanwater heats up, the zooxanthellae start producing toxins, which forces the corals to eject the algae back into the ocean. Without the zooxanthellae, corals lose a vital food source and slowly die. This process is known as coral “bleaching” because the colorful, living algae and corals are gone, leaving only the white limestone skeletons behind.
Climate change is causing a rise in overall ocean temperatures, as well as increasing the likelihood of localized temperature spikes. A chilling example of this was a ten-month long stretch of abnormally warm water around Christmas Island in the Indian Ocean from July 2015 to April 2016. In the months following the temperature spike, 90 percent of the reef’s corals died.
Another deadly trend fueled by climate change is ocean acidification. Every day, 90 million tons of carbon pollution is released into our atmosphere. About one-third of that carbon is absorbed by our oceans, which is gradually altering the chemistry of seawater and making it more acidic. The chemical changes make it more difficult for corals to acquire the nutrients they need to survive, causing a slower decline than bleaching, but with a similarly fatal end.
2. OVER-FISHING
Global demand for fish continues to increase, both for food and for the pet trade. Over-harvesting of fish to meet this demand is taking a toll on biodiversity and the ecological balance of coral reefs. Physically damaging fishing methods, such as trawling or using dynamite or cyanide in the water, can also damage or completely destroy coral reefs.
3. POLLUTION
Pollution affects our entire planet, including our oceans. A 2013 study found that fine airborne particles, produced largely by human industrial activities, actually block sunlight from reaching corals, which impacts photosynthesis and growth. Researchers examined coral reefs in Panama and Belize and found their growth rates have been slowing down since the 1950s because of this reduction in sunlight.
In addition, the 8 million tons of plastic that enter the world’s oceans each year disrupt countless numbers of marine plants and animals, including corals, who will eat tiny plastic pieces thinking they’re food. Many other sources of pollution, such as oil spills, sewage and agricultural runoff, also take a toll on coral reefs.
4. HUMAN ACTIVITIES
Irresponsible human recreation, such as careless swimming, snorkeling or diving, can damage coral reefs. Boating can also hurt coral reefs through noise pollution, dropping anchors on sensitive areas or collisions with wildlife.
Human coastal development is another threat. Sensitive marine areas are being dredged and disturbed to construct airports and buildings on land reclaimed from the sea. Also, building marinas, fish farms and other water-based structures can disrupt nearby coral reefs.
5. DISEASE
The frequency of coral disease appears to be on the rise, primarily by infection from bacteria, fungi or viruses. Scientists believe this is largely due to the increased environmental and physical impacts corals are currently facing, which weakens their natural defenses.
For example, an Australian study looked at the effect of permanent offshore visitor platforms that had been constructed within the Great Barrier Reef Marine Park. Researchers found that coral disease was up to 18 times more likely in reefs with platforms compared to undisturbed reefs.
WHAT YOU CAN DO TO HELP CORAL REEFS
The World Resources Institute has a great video summarizing their Reefs at Risk report, which examined the state of the world’s coral reefs and what we can do to bring them back to health. Check it out below.
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