Three tactics to buy time for the Great Barrier Reef
Le récif corallien est menacé mais il existe des solutions.
Visible depuis l'espace, la Grande Barrière de Corail est la plus grande structure vivante au monde. Située au large du Queensland, en Australie, elle couvre une superficie de 344 400 km2. La large diversité de vie marine qu'elle abrite lui a valu d'être inscrite sur la liste du patrimoine mondial de l'UNESCO en 1981. Malgré son immensité, elle est mise à mal par le tourisme de masse et surtout le réchauffement climatique. Ce dernier provoque un phénomène de blanchissement qui tue les coraux. Des solutions existent pour ralentir le processus mais font l'objet de débats tout autant scientifiques que politiques.
Can the world’s greatest coral reef system be rescued from the rapid march of the climate crisis? With global temperatures already about 1C higher than pre-industrial levels, Queensland’s Great Barrier Reef has been through three mass bleaching events in only five years. Corals are dying and the system is changing rapidly as temperatures keep going up and greenhouse gases keep accumulating in the atmosphere. 2. The Australian government has revealed a $150m research and development program to build the reef’s resilience to future warming. Ken Anthony, a principal research scientist at the Australian Institute of Marine Science, said: “It’s a bit like the Apollo 11 mission. It really is on that scale. We have to be able to look Australians in the eye in 10 years’ time and say that in the time we had, we did our best.” On its own, the project – called the Reef Restoration and Adaptation Program – is a clear signal that scientists now know cutting greenhouse gas emissions will not be enough to sustain a vibrant reef.
3. It’s time for intervention at a scale never seen before, scientists say, and they’re in a race against time to find enough solutions before climate change bites even harder. Some 43 concepts are being backed under the plan, from futuristic cloud brightening to using concrete blocks to stabilise damaged reefs.
4. The program has split the concepts into seven groups and scientists say none of them will be enough in isolation – it’s more likely that a combination deployed at different scales will give the reef the best chance. These seven categories fall broadly into three approaches: - Shading and cooling reefs to cut sunlight or lower ocean temperatures; - Stabilising and rebuilding reef structures damaged from bleaching, cyclones or ocean acidification; - Helping corals adapt to warmer temperatures and then moving their larvae around en masse. So what’s being planned, and could these approaches really buy the reef enough time?
SHADING AND COOLING THE GREAT BARRIER REEF
5. In early March, Daniel Harrison, a biological oceanographer at Southern Cross University, led a trial of equipment that sprays trillions of nanosized salt crystals into the air. The idea is the salt crystals reach existing low-level clouds and, because of their tiny size, encourage the formation of smaller cloud droplets that reflect more sunlight than larger droplets. The process mirrors what happens over the oceans every day as winds carry salty ocean spray into the air to help form clouds.
6. Harrison is leading a project to try to scale-up the trial to see if clouds over hundreds of kilometres could be brightened. If this was possible, the brightening effect could slightly lower ocean temperatures below – perhaps keeping corals just cool enough to prevent them from bleaching. 7. Such a system could be turned on and off quickly, and could be deployed when weather forecasts and models show that corals are under dangerous levels of heat stress. Harrison, who is leading the cooling and shading efforts under the government program, says: “It’s a combination of light and temperature that causes corals to bleach.
8. Other methods under this “shading and cooling” category include machines to create artificial low-hanging sea fog that could provide shade over smaller areas. Researchers are also looking at ultra-thin reflective films that could temporarily cut the sunlight over small areas.
STABILISING DAMAGED REEFS WITH SCAFFOLDING
9. Anyone who has walked around an ancient Roman city will have seen restorers working behind steel props and scaffolding that hold up what’s left of a once majestic temple or amphitheatre. Coral bleaching and cyclones can weaken the structure of reefs, known as the substrate. Scientists think that if reefs could be stabilised, it might give other methods a chance to take hold and restore individual reefs.
10. There are question marks over the economics of deploying mesh or 3D printed frames at scale, but the restoration programs suggest there could be small-scale deployments that could help reefs recover. Removing natural
“It's time for intervention at a scale never seen before”