Reef In Peril

The world’s largest living reef, visible from space, is in rapid decline thanks to threats ranging from an acidifying ocean to an outbreak of coral-destroying starfish. Will the priceless natural wonder be able to recover?

Almost all of us have seen the frightening headlines scroll through our social media timelines: “Half of the Great Barrier Reef is Dead” or “The Great Barrier Reef: Bleached Beyond Repair.” These headlines are rightfully terrifying, accurately illustrating the damage the Reef has endured thanks to man’s wanton environmental disregard.

The Great Barrier Reef is in very warm water, both literally and figuratively. The headlines have done a great job of making us aware of the dire situation, but many people do not dive deep enough into the associated articles to understand that, while overwhelming, the threats facing the Reef can be mollified with united conservation efforts from both Australia and the rest of the world. It’s not too late to reverse the troubling trend and help this World Heritage Site rebound.

Part One: The Threats

A key means to help preserve the remaining (relatively) intact areas of the Reef is to understand the threats it faces. The fundamental cause is man’s industrialization and the resulting climate change. As energy began to be created in mass quantities by burning fossil fuels in factories, greater amounts of gases, like carbon dioxide (CO2), were released into the atmosphere. CO2 and a variety of other gases, including methane from cows and natural gas, act like a blanket over the earth, trapping solar energy as it is reflected by the earth and trapping it in the atmosphere, creating a warming, or “greenhouse effect”. As more light is trapped by the blanket of greenhouse gases, the surface of the earth warms as well as the world’s oceans.

But exactly why the Great Barrier Reef is doing so poorly in this warming world is slightly more nuanced. Logically, a warmer ocean would mean more coral reefs, incredibly diverse environments that require warm water to thrive. But the excess CO2 in the atmosphere causes the oceans to become more acidic as the ocean absorb the excess from the atmosphere. The ocean is slightly basic (pH>7) and as it acidifies and becomes more neutral in pH, coral fares as well as you would in a vat of acidified liquid.

An acidifying ocean changes everything for coral, which are tiny animals related to jellyfish. They cannot easily form their calcium carbonate skeletons, which act as the bedrock for coral reefs, because less carbonate ions are available in acidic seawater. Corals are pretty much hindered from growing by ocean acidification, and will start to dissolve soon if emissions continue to rise. Outside of the chemistry of the water, temperature and light levels are key. Corals exposed to increased temperatures and increased amounts of light over a duration of time (sometimes only a couple of days) will become stressed and eventually bleach. The corals become ghost white as they are forced to expel symbiotic algae (called zooxanthellae) from their tissue as they cook under intense light and heat. The zooxanthellae are crucial to the coral, turning sunlight into energy through photosynthesis. The coral is not dead when it bleaches, but it is essentially starving. Bleaching events usually create mass coral mortality.

In the Great Barrier Reef, the 1-2 threat of ocean acidification and coral bleaching have become more destructive over the last few decades as the oceans continue to warm and CO2 continues to be pumped into the atmosphere. Severe bleaching used to ravage a reef every 27 years. Since the 1980s, these events have occurred roughly every six years. The first truly severe bleaching event of the Great Barrier Reef was in 1998, but the following bleaching event, in 2002, was disastrous, bleaching over 50% of the Reef.

But the 2002 monster bleaching event was dwarfed by one in 2016, when 80% of a large protected swath of the northern Reef was killed by heat stress. Badly bleached reefs need at least 10 years to rebound, but the Great Barrier Reef barely had time to catch its breath as a similarly unprecedented bleaching event hit the reef in 2017, wiping out 20% of the total coral cover. Since the massive warming event in 2016, over half of the Reef’s coral has died, particularly devastating the northern area of the Reef.

Like other threats the Reef faces, the crown-of-thorn starfish (COTS) outbreak can be tied to human impact on the oceans. The most prevalent hypothesis of what causes COTS outbreaks, which feature over 30 times the natural COTS density, is the added nutrient levels on reefs caused by nitrogen- and phosphorous-rich runoff from agriculture. The increased amount of nutrients cause blooms of phytoplankton that offer plenty of food for COTS larvae. COTS outbreaks can also be linked to the removal of the venomous starfish’s predators, such as the giant triton snail, titan triggerfish and humphead Maori wrasse from the reefs through overfishing.

COTS outbreaks can prove fatal when combined with climate change. COTS outbreaks have been found to strip 90% of a reef’s living coral tissue. A healthy reef is capable of recovering from COTS outbreak in 10-20 years, but a stressed reef in warming water may never be able to recover. Moreover, these outbreaks appear to be occurring more frequently in recent years. A variety of methods is being tested to control the ruthless corallivores, from harvesting them with divers to injecting them with compressed air, but the starfish has been able to run rampant throughout the Great Barrier Reef.

Part Two: What Can Be Done

With half of the Reef’s coral dead, one of the most incredible natural wonders really seems to be heading toward the brink. Experiments are being conducted to find out ways to better equip coral to survive bleaching events. There is a dizzying variety of coral in the world’s oceans, especially in a corridor between the Pacific and Indian Oceans fittingly called the “Coral Triangle”, and not all coral’s respond to bleaching the same way. Researchers in Hawaii have researched how hardier corals react under the warm and acidic conditions they will face later this century. Depending on how well each species responds, they will be selectively bred with other resistant corals to form a sort of “super coral” through assisted evolution. Other projects have focused on trying to figure out ways to reinsert zooxanthellae into bleached corals. Some hypothesize that certain types of the symbiotic algae may be better suited in warmer water and will not be expelled from their hosts as quickly.

The hope with these projects is to engineer stronger coral and zooxanthellae that will be able to survive in the “new normal” environmental conditions caused by humans. This reactionary approach will always be similar to putting a bandaid on a wound. It will provide some level of healing but will not remedy the underlying causes. Humans everywhere need to cut back on emissions to slow the rapid change of our climate.

Australia, in particular, needs to continue to fight the Carmichael coal mine, a billion dollar fossil fuel-monstrosity that could be the largest in Australia’s mining-heavy history and would be located just inland from the Reef. The mine, which was approved after a lengthy (and probably still ongoing) legal battle, plans to extract at least 25 million tons of coal per year which will result in 77 million tons of CO2 emissions. Most of the coal will be exported from Australia to India, which means transporting it over the Reef in large ships that leave pollution, sediment, and invasive species in their wake. For coral reefs to have any shot in the future, global temperature rise must be capped at around 1.5 degrees Celsius. Achieving that goal would be even more challenging as super-mines, like the Carmichael mine, continue to provide incredible amounts of fossil fuels to developing countries with huge populations like India.

Some less staggering goals are fishing more responsibly and curbing the amount of agriculture runoff from the coast along the Great Barrier Reef. Both of these will act in tandem to limit COT outbreaks and limit the growth of algae on reefs. Algae, which thrives in nutrient-rich water, is encroaching on coral’s turf as more nutrients are flushed into the ocean and herbivorous fish that eat the algae are overfished. In the Caribbean, a die-off of herbivorous sea urchins in the 1980s led to dense thickets of algae usurping reefs throughout the area. Could the Great Barrier Reef be next?

A variety of measures will have to be taken to address the plethora of problems ravaging the world’s largest reef. An important point that is often lost among the devastation is that we can all play a part, no matter where we live, by changing how we live. This involves being smarter about emissions and continuing to fight the creation of large fossil fuel operations, like the Carmichael mine, that not only threaten coral reefs, but everywhere on earth.

Part Three: Why Save the Reef?

Heron Island is a half mile-long speck of sand inhabited by thousands of birds, a small resort and a world-class coral research station.

I was lucky enough to visit the Great Barrier Reef twice during my semester abroad, including spending five days on the University Queensland’s Heron Island Research Station, which is located at the southern tip of the immense reef. This area was sheltered from the worst of the recent mass bleaching events thanks to a cyclone in Fiji that sent crucial cool water westward.

As someone relatively new to scuba diving who hails from the Great Lakes region (Chicago) far from the tropics, the breathtaking assortment of marine animals and coral was overwhelming. The variety of coral formed a kaleidoscope of soft yellows, pinks and greens as small fish darted between the large branching coral and squat, round brain corals. Large parrotfish, whose gaudy colors reflect the coral, messily chomped on the algae growing on the coral’s surface, sending chunks flying every which way. A snowflake moray eel, splattered with bright yellow and black spots, bared its teeth at me as I drifted a little too close to its rocky crevice. Around 10 percent of the world’s fish species can be found in this one reef system.

Sea turtles lazily hunkered down on top of the coral or leisurely swam by, beating their fins every so often. Six of the world’s seven sea turtle species come to the Great Barrier Reef to breed, including the endangered loggerhead sea turtle whose females hoists their bodies up on the beaches of Heron Island to nest. Many were born at this same spot. Giant cow-tailed rays, each one bigger than the last, silently glide along the seafloor as eagle rays flap their wings along the outskirts of the reef, effortlessly flying through the water. Small white-tipped reef sharks joined them there, wary of the divers that had entered their reef. The Great Barrier Reef is home to 134 species of rays and sharks, including species as iconic as the manta ray and tiger shark. Many are at risk, reflecting the global trend of shark decline.

The Great Barrier Reef is one of the world’s greatest natural wonders, spanning an area as big as Italy and housing thousands of species. Besides its intrinsic value as an incredible biodiversity spot, it attracts people from around the world and generates billions of dollars for the Australian government each year. Although it has been hit hard in the last few decades, the recovery of portions is still possible. We do not want to be the generation that let the world’s greatest reef erode into oblivion.

All pictures and art by Jack Tamisiea.

Sources:

https://www.nationalgeographic.com/magazine/2018/08/explore-atlas-great-barrier-reef-coral-bleaching-map-climate-change/

https://oceanservice.noaa.gov/facts/coral_bleach.html

https://www.theguardian.com/business/2017/aug/16/why-adanis-planned-carmichael-coalmine-matters-to-australia-and-the-world

https://www.newyorker.com/magazine/2016/04/18/a-radical-attempt-to-save-the-reefs-and-forests