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Mass outbreaks of starfish, pollution from agriculture and a hotter sea leading to coral bleaching. Lately, the Great Barrier Reef has long been subject to a number existential challenges. Now a series of efforts are aimed at reversing the trend.

Blacktip reef sharks circle around some green sea turtles that feed on algae on the corals. Stingrays brush past along the sandy bottom. Suddenly, a few dolphins join in, looking to hunt with the reef sharks. We dive near the coral reef that surrounds Lady Elliot Island, a small island at the southern tip of the Great Barrier Reef, in Queensland, Australia. It’s easy to understand why the area is world-famous among divers. But the fantastic underwater scenes are giving us mixed emotions. How long are they going to be around for?

The northern – and warmer – parts of the Great Barrier Reef are now known for completely different things. As the water temperature rises, the corals’ defenses are adversely affected. The corals, which are living organisms, can end up dying as a result. The phenomenon is more commonly known as coral bleaching. The mass die-offs that hit the northern areas in 2016 became international news, and the following year was just as bad.

Coral bleaching and climate change

Reports on how much of the whole barrier reef has been affected by coral bleaching vary. However, at least half of the corals in the areas examined are estimated to have been bleached and are either partially dead or completely dead.

Coral bleaching is not a new phenomenon. In the past, severe bleaching has occurred approximately every thirty years. Since the 1980s, the frequency has increased to once every six years. And in 2016 and 2017, bleaching occurred two years in a row.

Usually it takes at least ten years for the corals to recover, but if the bleaching occurs at shorter and shorter intervals, then it becomes difficult for the corals to rebound.

Global sea temperatures have risen throughout the course of history, and the coral reefs have survived. But in the past, changes occurred over long periods of time. Never before has the bleaching occurred as quickly as is currently happening. Now the researchers are asking: Can technical assistance contribute to rescuing the world’s coral reefs?

Super coral crossbreeds occupy the reef

The Australian Institute of Marine Science (AIMS) is located outside of Townsville in the north of Queensland. Here, researchers are investigating how so-called “super corals” – corals that can withstand higher water temperatures – could be distributed over large areas. Inside AIMS, around 25 strains of corals are being crossbred in a sea simulator, which is considered the world’s most advanced research aquarium. Species from the northern parts of the reef are being mixed with from those from the colder central and southern parts of the reef.

“It’s like crossbreeding corn. We are doing the same with the corals so that they can withstand higher temperatures,” says Kate Quigley, a researcher in reef restoration.

The method is called assisted gene flow and is still in its infancy; however, it’s already showing positive results in the sea simulator as well as on the reef where cross-bred corals have been placed in coral cultures.

In order for the super corals to have an effect on the Great Barrier Reef – which is approximately 1,400 miles (2,300 kilometers) long – it is necessary to spread the corals over large areas while they are still in the larval stage. The larvae grow in cages and are then placed in strategic locations. Kate Quigley and her colleagues hope that within three years it will be possible to spread hundreds of thousands of individual farmed corals over reefs that have been affected by bleaching.

At the same time, climate change is hanging like a dark cloud over their progress.

“Hundreds of studies have been conducted that show that climate change is the greatest threat to the reef,” says Kate, but at the same time, she clarifies that the global fluctuations look different.

The enemy of my enemy…

AIMS is also researching ways to reduce the number of crown-of-thorns sea stars – a starfish whose quantities have exploded in certain parts of the reef. To date, divers have injected the crown-of-thorns sea stars with vinegar – a method that kills the starfish. Now researchers at AIMS are working on how a natural enemy to the crown-of-thorns sea stars – the rare Giant Triton snail – might be deployed and proliferate in areas it has disappeared from. The giant snail is highly sought for its shell, and as a result, its stocks have been depleted in many places – another reason why the crown-of-thorns sea stars have been able to grow in number unimpeded, in turn upsetting the natural balance.

Agriculture impacts coral reef

Over the years, much of the coral die-offs on the Great Barrier Reef – particularly in the media – have been blamed on Queensland farmers who, through their farming practices, are said to have caused large amounts of nutrients, such as phosphorus, to leak onto the reef. This in turn causes algae blooms that cover the corals.

Recently, attitudes have changed among many of the Queensland farmers and they now want to develop more sustainable farming practices. Thousands of farmers and livestock breeders are involved in projects that are aimed at reducing sediment, nutrients and insecticides in wastewater.

Gary Spotswood is a third-generation farmer at Mt Alma Organics, an organic farm just over an hour outside of Townsville. On his farm, he has installed, among other things, pumps to capture wastewater, which is then filtered naturally through wetlands that cover part of the land. The results can already be seen. A lagoon spreads out next to a field of sugarcane. Suffocating weeds had previously covered the water, says Gary Spotswood. These days, it’s clear and free of weeds.

We need to change our behavior

Gary Spotswood also holds courses in land use for other farmers in the area. Artificial fertilizers are expensive and price is another reason why many farmers want to switch to more sustainable alternatives. According to Gary Spotswood, the best alternative for the area’s dry lands is supposedly a mixture of the residues from sugarcane and compost from aquatic plants. The mixture binds to the carbon and nitrogen in the soil and the nutrition stays in the soil longer while water is simultaneously retained in the plants’ root systems.

“Changes take time but in five years, people have changed their habits in how they use the soil. It’s a win-win because in the end, it’s also about being cost-effective.”

But despite improvements in the area’s agriculture, Gary thinks there is another, much more important issue that the world should be acting on.

“Climate change is by far the biggest threat to the reef ’s survival.”




Johan Augustin
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