Why Coral Reefs Are Dying (What Can Be Done About It)
Coral reefs are valuable ecosystems that support a wide range of marine life. Unfortunately, human activities and climate change have caused a serious imbalance in their natural conditions, resulting in the death of many of these aquatic habitats.
However, the ins and outs of why and how coral reefs are dying is a bit more complex. Here’s a brief overview of what’s going on and how to prevent further losses.
Why Are Coral Reefs Dying?
Coral reefs are sensitive to small changes in their environment that alter the delicate balance they depend on to survive. Coral reefs also support entire ecosystems: about a fourth of all marine species depend on coral reefs for food and habitat. Coral is a bellwether species. When a coral reef starts to decline, scientists may use that as an indicator that something’s amiss with the quality of the water, seabed, or other aspect of environment.
In the past 50 years, about half of all coral reefs have died, and up to 90% of all coral reefs may be gone by the end of this century. The main threat to coral is climate change.
Climate Change: The Primary Threat
Climate change is killing the world’s coral reefs by increasing the temperature of seawater. As seawater warms, corals lose the microscopic algae that lives in their tissue and nourishes them. Without this algae, corals lose their distinctive bright colors and appear white in color, since all that’s left is their calcium carbonate skeleton. This phenomenon is called coral bleaching. Significant coral bleaching can kill entire reefs or weaken them so that they’re vulnerable to disease.
Climate change is also a threat to coral reefs because of ocean acidification. As more carbon dioxide is emitted into the atmosphere, the ocean absorbs more carbon dioxide and becomes more acidic. Since the Industrial Revolution began about two centuries ago, the ocean has become 30% more acidic — and scientists estimate it will become even more acidic over the next century as we continue to pump more carbon dioxide into the atmosphere. A more acidic ocean hampers the growth of coral’s calcium carbonate skeleton.
Natural Threats
Coral reefs can also be put under a great deal of stress due to natural threats, which makes them vulnerable to diseases such as white band disease.
A few examples of natural stresses that can cause coral reefs to become sick include:
- Fungi
- Bacteria
- Ultraviolet radiation
- Storms
- Viruses
Any of these threats could wind up causing life-threatening effects for reefs.
Threats from Humans
Besides climate change, there are many other human threats that also harm coral reefs. Destructive fishing practices, overfishing, undersea mining, coral harvesting, tourism, and pollution can wipe out a coral ecosystem in a couple of weeks or months.
Industrial fishing that relies on chemicals, explosives, and trawls seriously damage coral reefs. When these methods are used to harvest fish that live in coral reefs, the coral may never grow back. Overfishing upsets the natural balance of a coral reef.
Pollution can damage or kill coral reefs, too. Herbicides in agricultural runoff that flows into the sea can kill the symbiotic algae that live inside corals and provide them with energy. This can trigger coral bleaching and death. Other toxic substances like mercury, lead, and organic chemicals in urban stormwater runoff can affect corals’ growth and reproduction.
Agricultural runoff containing fertilizers — mainly nitrogen and phosphorus — can lead to an overgrowth of algae on coral reefs. The overgrowth disrupts the balance of the ecosystem, consuming the oxygen in the seawater that corals require and supporting the growth of harmful bacteria and fungi.
What Can We Do to Stop Damaging Coral Reefs?
If we want to save coral reefs, we need to try and limit our greenhouse gas emissions/footprint. Obviously, this is a global problem that international organizations and governments are tackling, not something that individuals can resolve on our own.
However, as individuals, we can still do something to help coral reefs. For example, we can share knowledge, raise awareness about the threats to coral reefs, and support organizations that are working to save coral reefs.
As individuals, we can also fight climate change by reducing our own carbon footprints.
Respect Coral Reefs
If you’re vacationing in an area with coral reefs, be sure to respect these fragile ecosystems. Be a responsible tourist and follow local rules. Don’t fish or swim near coral reefs that are off-limits to people. If diving or snorkeling near a coral reef is permitted, always follow the “look, don’t touch” rule. Don’t collect any corals or any other sea life to take home.
If you’ll be swimming in an area near a coral reef, you may also want to use a sunscreen that does not contain chemicals that can damage corals. Sunscreens with the ingredients oxybenzone, octinoxate, and avobenzone can harm coral reefs. Instead, consider using “reef-friendly” sunscreens that contain only zinc oxide or titanium dioxide, if possible, depending on your skincare needs.
