When you daydream about your next incredible diving vacation, you probably picture a vibrant coral reef. Bright rays of golden sunlight burst through crystal-clear waters to illuminate a world filled with non-stop life and color. You probably don’t think about the murky depths of mangrove forests, characterized by darkness and poor visibility. Divers rarely give these ecosystems a second thought, but mangroves are essential to your next great dive.
Mangroves and Coral Reefs
Mangroves are crucial to coral-reef survival. Corals get most of their energy from microscopic algae living inside their cells called zooxanthellae. These tiny plants use solar energy to photosynthesize, providing the host corals with enough energy to build their external skeletons. They also provide corals with their many distinctive colors. This dependence on the sun for survival means that corals rely on clear water, and mangroves act as natural water-treatment plants, providing corals with just that. They stand sentinel between the land and sea, stabilizing the shoreline to prevent erosion and removing pollutants from the water. Their complex root systems trap everything that would otherwise drift out to nearby reefs and smother unsuspecting corals.
Mangroves as Nurseries
Mangroves are also important nurseries for your favorite reef fish. Next time you’re diving on a coral reef, watching the parrotfish, butterflyfish or the great barracuda swim by, take a moment to wonder where they came from. Great barracuda can grow to almost five feet (1.5 m) long and weigh over 50 pounds (23 kg) but, just like us, they have to start somewhere. Picture the juvenile great barracuda. Only two inches (5 cm) long, they depend on the protection of tangled mangrove roots and the cloaking darkness of the sediment they trap to survive. Without mangroves, these juveniles would be forced out into the ocean at sizes far too small to escape predation.
Mangroves and Climate Change
Mangroves also help protect corals from the harmful impacts of global climate change. Reef-building corals prefer temperatures between 73 to 84 F (23 to 29 C). If water temperatures rise above this level for long enough, the zooxanthellae living inside the corals become stressed and abandon ship, leaving corals without their main source of energy or their color. This is known as coral bleaching. If sea temperatures return to normal soon enough, the zooxanthellae may return and the coral may survive. But if temperatures remain high for too long, or the coral is stressed in another way, it will die.
Greenhouse gases, such as carbon dioxide (CO2) and methane (CH4), are the main cause of global climate change. When we release these gases into the atmosphere they insulate the Earth, increasing its average temperature. Humans emit greenhouse gases in a variety of ways. Combustion of fossil fuels in vehicles, electricity production, and the removal of forests, which would otherwise store CO2, to create more grazing land for food animals.
A Blue-Carbon Reserve
On land, carbon stored within natural reserves, like forests, is called ‘green’ carbon. In the marine environment, it is termed ‘blue’ carbon. Coastal vegetation, such as mangroves, are blue-carbon reserves. These are capable of storing up to five times more carbon, up to 100 times faster than other tropical forests. Their complicated root systems slow incoming tides, forming large deposits of rich organic material. This soil is capable of storing more carbon than most tropical forests have in their biomass and soil combined. Mangroves quite literally slow the tide of global warming, helping protect our much-loved coral reefs.
Unfortunately, mangroves don’t often receive the love and protection they deserve. Although they are crucial to the health of coral reefs, as well as supporting the livelihoods of many coastal communities, their seemingly “dirty” appearance means they are often destroyed to make room for projects that are seen to have more monetary value. All over the world, mangrove forests have been removed in favor of coastal development such as shrimp farms, agriculture, marinas, roads and tourism. Almost 600 square miles of mangrove wetlands are lost each year to a combination of climate change and coastal development impacts. If this destruction continues, your next dive on your favorite reef will look very different.
What You Can Do
In the same way that coastal and marine ecosystems are connected, so too are our actions. Choosing to eat shrimp curry may mean that you’re supporting an industry that destroys mangroves, leaving 75 percent of tropical fish without a safe place to grow up. (And eating wild shrimp caught via a trawler is no better). Choosing to stay in a hotel right on the beach may mean that you’re supporting an establishment that has cleared away a mangrove forest and consequently a local community’s only source of income as well as environmental protection from storm surge.
Make informed decisions. In the same way that you research potential dive sites and gear-rental costs, research the green initiatives of the places you want to visit. Does your hotel recycle? Do local restaurants source their seafood sustainably? Does your dive center promote environmental standards? Basing your choices on decreasing your environmental impact will create a demand for sustainability, which the tourism industry is more than capable of providing. Most importantly, tell people how and why you made your decisions. Tell your friends why you’re staying where you’re staying. Tell your dive-center manager why you chose to dive with them. Compliment and tip your dive guide when he corrects your buoyancy and helps you avoid damaging the reef. Tell your dinner restaurant why you’re leaving shrimp — and perhaps all seafood — off your plate.
If you’re looking for a green dive center, start with the Green Fins website. Green Fins is a management approach designed by the United Nations Environment Programme and internationally coordinated by The Reef-World Foundation. It provides the only internationally recognized environmental standards for the scuba diving and snorkeling industry. Over 400 operators across Asia have committed to improving their practices above and below the water by following the Green Fins environmental code of conduct.
Use the website to find active Green Fins members at your desired destination. Drop them an email to let them know how you found them. Ask them about their environmental policies. Ask them if they’re taking part in any conservation initiatives like underwater clean-ups. And next time you’re appreciating an exquisitely weird frogfish (having been sure 30 seconds ago that it was just a bit of sponge), take a moment to appreciate the mangroves that have kept the water clear enough for that little guy to survive.