Australia’s northeastern coast is home to the Great Barrier Reef, the world’s largest living structure. About 10% of the world’s coral reef ecosystems are found in this region. The 2,500-reef network covers 348,000 km2.
Unfortunately, the magnificent reef is quickly becoming the world’s largest dying structure, according to a paper recently published in the journal Nature. This evaluation was based on a survey done by biologist Terry Hughes of James Cook University in Queensland, Australia. Hughes is the director of the university’s Arc Center of Excellence for Coral Reef Studies.
Last year, the researchers reported a considerable bleaching episode that happened over several months, ruining two-thirds of the northern part of the reef. This year, Hughes’ crew has more bad news: a more extensive bleaching outbreak is underway along a 500-mile section of the reef south of last year’s disaster. These consecutive occurrences have resulted in the most significant coral bleaching ever recorded, affecting two-thirds of the entire Great Barrier Reef.
Overall, the Great Barrier Reef has lost half its coral since 1995.
What is Coral and Coral Bleaching
Coral is made up of tiny organisms called polyps, which are responsible for the animal’s bright colors. The polyps eat reef-dwelling algae and microplankton.
The polyps and algae live in a symbiotic relationship. The algae produce sugars through photosynthesis, giving the coral most of its nutrients. The polyps supply the algae with nitrogen and carbon dioxide.
However, algae are sensitive to variations in water temperature. So when the temperature of the ocean goes up, the chemicals that algae make become poisonous. The coral responds by ejecting the toxic algae and polyps, turning white.
Bleached coral is only stressed, so it’s still alive, but prolonged heat stress eventually causes the coral to die of malnutrition. So, if water temperatures decrease, bleached corals may restore their color and survive. Such an occurrence took place in 2020; coral mortality was very low after a mass bleaching event.
Details on the Bleaching Episodes
Early in December 2021, the Great Barrier Reef’s waters warmed above record summer maximums. Unfortunately, ocean temperatures continued to rise until early April 2022, causing thermal stress in the Central and Northern Great Barrier Reef (GBR). This led to the fourth mass bleaching of the Great Barrier Reef in seven years and the first to occur during La Niña conditions.
Hughes said in an interview with Yale Environment 360:
“The phenomenon that we are seeing now is a very modern issue for reefs. Until an El Niño event in 1982-83, mass bleaching at the scale of, say, the Caribbean basin or the Western Pacific or the Indian Ocean was unheard of. The first completely global bleaching event was in 1998. That was a wake-up call for people here in Australia because that was the first time ever that the Great Barrier Reef had bleached.”
Climate Council researcher Simon Bradshaw said:
“This is heartbreaking. This is deeply troubling. It shows that our Great Barrier Reef really is in very serious trouble indeed.”
The most recent survey reported that 91% of the areas analyzed were affected (654 of 719 reefs).
David Wachenfeld, the chief scientist at the body that regulates the reef environment, said most of the coral should recover from the current catastrophe. He said:
“The early indications are that the mortality won’t be very high. We are hoping that we will see most of the coral that is bleached recover, and we will end up with an event rather more like 2020 when, yes, there was mass bleaching, but there was low mortality.”
Some researchers, like Hawaii’s Ruth Gates, are producing warmer-water-resistant coral in the lab and then releasing them into the wild. However, artificial breeding is inefficient and a long shot.
Hughes expressed his doubt about the approach during the interview. He said:
“The idea is you raise coral in an aquarium at elevated temperatures, so they are adapted to those temperatures, and then you put them out into the wild, and over time they infiltrate into the wild population and replace the more susceptible individuals in that population. I have a problem with the scale of that because the size of the wild populations is vast, and adding, say, 1,000 aquarium-bred individuals into the wild is not going to make a significant difference to the gene pool.”
Climate Change is to Blame
Hughes blames climate change for the Great Barrier Reef’s destruction. He said:
“The catastrophic damage to Australia’s reefs is part of a global phenomenon that is threatening the survival of coral worldwide and is a clear warning that we need to rein in greenhouse gas emissions. We simply cannot afford to continue with business as usual. We are very concerned that these events are getting more frequent. The reef simply won’t come back if we have a bleaching event every other year.”
Climate change threatens all coral reefs. Carbon dioxide emissions from fossil fuels, agriculture, and land clearing cause climate change. In addition, human activities have pushed the world average temperature 1.0°C above pre-industrial levels already.
This warming is expected to cause increasing destructive maritime heatwaves. Meanwhile, global warming is causing changing weather patterns, ocean acidity increase, and rising sea levels – all of which will affect coral reef ecosystems as well.
Since the industrial revolution, oceans have absorbed a third of human-made carbon dioxide, making them more acidic. Even minor increases in acidity limit corals’ capacity to grow skeletons and shells, reducing reef habitat. Weakened coral skeletons lose their ability to resist and recuperate from tropical storm damage.
In addition, coral loss reduces fish and related species.
If greenhouse gas emissions continue to rise at the current rate, the Great Barrier Reef might experience bleaching twice per decade by 2035 and annually by 2044.
Thus, robust global climate change action is essential to save the Great Barrier Reef and other reefs worldwide. If greenhouse gas emissions continue, global temperatures will rise dramatically, and the Reef’s health will suffer, affecting businesses and communities who rely on it.
Politics May Determine the Fate of The Great Barrier Reef
The recent bleaching event serves as an uncomfortable reminder of the disparities in climate change policy among Australian lawmakers. The conservative government has set less ambitious carbon reduction targets than the center-left opposition. The Liberal Party of Prime Minister Scott Morrison plans to cut Australia’s emissions by 26% to 28% below 2005 levels by 2030. The opposition Labor Party has pledged to cut emissions by 43% by the end of this decade.
Morrison was criticized during the November U.N. climate conference for not setting a more aggressive aim. Greenpeace Australia Pacific called the latest bleaching another scathing indictment of the Morrison administration, which has failed to safeguard the reef; instead, aggravated the crisis by supporting fossil fuels.
Lissa Schindler, an Australian Marine Conservation Society campaign manager, called the findings devastating news for everyone who loves the reef. Her words:
“This was a La Nina year, normally characterized by more cloud cover and rain. It should have been a welcome reprieve for our reef to help it recover, and yet the snapshot shows more than 90% of the reefs surveyed exhibited some bleaching. Although bleaching is becoming more and more frequent, this is not normal, and we should not accept that this is the way things are. We need to break the norms that are breaking our reef.”
Only significant and swift efforts to reduce global greenhouse gas emissions will help the Great Barrier Reef. If we want to protect the Reef and the communities and companies that depend on it, we must act NOW.
Even with rapid and substantial action to cut global emissions, greenhouse gas in the atmosphere will continue to harm the Reef. Therefore, limiting global temperature rise to the Paris Agreement benchmark of 1.5°C this century is a must.
