Coral reefs are some of the most diverse and important ecosystems on Earth. While they cover only .1% of the ocean floor, they are home to a quarter of all marine life -- from thousands of species of fish, sea turtles, and millions of other organisms. They all depend on coral reefs for their survival, which is why they are called the rainforest of the sea.
Coral reefs also play an important role in human lives. They provide food and protection of shorelines, creating jobs based on tourism. They provide key nutrients and proteins for one billion people around the world, protecting coastlines from erosion, storm surges, and enhancing tourism economies. Coral reefs are valued at $172 billion each year across the world.
However, the world’s coral reefs are in grave danger due to global warming and climate change. Recent studies have revealed that 50% of coral reefs have already been destroyed and that all corals will be threatened by 2050 while 75% will face high to critical threat levels. Many experts also believe that the very existence of coral reefs may be in jeopardy unless countries intensify their efforts to protect them.
“Children born today may be the last generation to see coral reefs (...) unless we do everything to limit warming to 1.5C, we will lose 99% of the world’s coral reefs,” David Obura, chair of the Coral Specialist Group in the International Union for the Conservation of Nature, said.
The Threat to Coral Reefs
The decline of coral reefs across the world continues at an alarming speed, and one of the biggest reasons is coral bleaching due to global warming. It happens when heat stress causes the coral to release its brightly colored algae, leaving it completely white. There’s a high possibility that the corals would starve to death if the bleaching event lasts for more than a couple of weeks. When this happens, they could die and could no longer provide a habitat for the surrounding marine life.
A 2017 study revealed that at least 25 out of the World Heritage reef systems will experience twice-per-decade severe bleaching events by 2040. UNESCO stated that this frequency will “rapidly kill most corals present and prevent successful reproduction necessary for the recovery of corals.” “These are spectacular places, many of which I’ve visited. Seeing the damage being wrought has just been heartbreaking. We’re to the point now where action is essential. It’s urgent,” Mark Eakin, a reef expert with the National Oceanic and Atmospheric Administration, said.
Previous studies have shown the link between heat exposure and bleaching, revealing how reef areas have suffered the most severe damage where heat exposure was most extreme. In 1911, the first recorded bleaching occurred on Bird Key Reef in the Florida Keys during a period of hot weather, causing 5% to 10% of the reef lost. According to Sloactive, a social enterprise dedicated to protecting our oceans, many more mass bleachings happened after that, with one of the worst occurring from 1997 to 1998.
National Geographic, an American pay television network and flagship channel that is owned by National Geographic Partners, reported that 25 reefs, which comprise three-fourths of the world’s reef systems, have experienced severe bleaching events in the past six years in what scientists concluded was the worst-ever sequence of bleachings to date. While the Great Barrier Reef was especially hard hit, other reefs have also suffered severe bleachings such as Seychelles, New Caledonia, 750 miles (1,210 kilometers) east of Australia, and the US.
"The last three years have been extremely depressing for me. We're seeing truly catastrophic damage to many reef systems around the world. The Great Barrier Reef damage we've seen is greater than anything we've seen in the past 20 years,” Eakin said.
Global Warming Could Eliminate Coral Reef Habitats By 2100
Hugh Sweatman, the head of the long-term monitoring program at Aims, stated that the capacity of the world’s coral reefs to recover is still under threat from climate change, as well as other chronic stressors such as pollution. For instance, while the whole Great Barrier Reef improved dramatically between 2012 and 2016, it suffered an unprecedented loss from the 2016 bleaching. According to The Guardian, a British daily newspaper, that single event killed about a quarter of the reef’s coral.
A recent study conducted by researchers from the American Geophysical Union revealed that coral reefs across the globe are facing uncertain futures as ocean temperatures continue to climb. Initially, experts predicted that 70% to 90% of coral reefs will disappear over the next 20 years as a result of climate change and pollution. However, recent research mapping discovered that coral reefs could disappear by 2100 due to rising sea surface temperatures and acidic waters.
"By 2100, it's looking quite grim," Renee Setter, a biogeographer at the University of Hawaii Manoa, said.
In the study, the researchers mimicked future ocean conditions like sea surface temperature, wave energy, acidity, pollution and overfishing in areas where corals are today. They wanted to map what areas of the ocean would suitable for coral restoration efforts over the coming decades. Their findings, unfortunately, showed that most parts of the ocean where coral reefs exist today won't be suitable habitats for corals by 2045. This situation worsened as the simulation extended to 2100.
According to Science Daily, an American website that aggregates press releases and publishes lightly edited press releases about science, the results of the study emphasized how Earth's warming climate could have devasting impacts on marine life. This suggests that corals are most at risk from emission-driven changes in their environment. "Trying to clean up the beaches is great and trying to combat pollution is fantastic. We need to continue those efforts. But at the end of the day, fighting climate change is really what we need to be advocating for in order to protect corals and avoid compounded stressors,” Renee Setter, a biogeographer at the University of Hawaii Manoa, said.
Another important finding is that the team predicted that a mass bleaching will happen within the next couple of weeks in Australia's Great Barrier Reef. The World Economic Forum, an independent international organization committed to improving the state of the world, predicted that this is likely to happen if high ocean temperatures around the reef do not drop in the next two weeks. "Unfortunately we are a whisker away from bleaching disaster yet again because of global warming-driven marine heatwaves," Shani Tager from the Australian Marine Conservation Society to the Australian Broadcasting Company said.