A list of 43 ideas to save coral reefs, many of them desperate long-shots, has been released as Australia faces the loss of one of its most precious assets, the Great Barrier Reef (GBR). Some trials have already begun in the hope of establishing which ideas can protect individual reefs. Those that succeed will be assessed for their capacity to scale up to defend a global wonder 2,300 kilometers (1,400 miles) long.
After years of denial of the dangers faced by the Great Barrier Reef, the Australian government announced in 2018 the allocation of $500 million to address the threats. The Reef Restoration and Adaptation Program (RRAP) has considered 160 ideas, of which 43 have now been announced as having sufficient potential to justify further investigation.
Hotter summers are generally considered the greatest threat to Australian corals, leading to three enormous bleaching events in the last five years. Consequently, three of the ideas, including those that have attracted the most attention, involve reducing summer temperatures:
- Spraying seawater above the reef to use the presence of salt to increase the sunlight clouds reflect back to space.
- Inducing fogs over targeted reefs, again through spraying seawater.
- Spreading a molecule-thick layer of calcium carbonate on the surface of the ocean to cut sunlight by 20 percent.
Pumping cooler water from deep water has been rejected as impractical on the scale required, even for small high-priority reefs.
The effectiveness of all of these remains untested. Indeed, RRAP Executive Committee Chair Dr Paul Hardisty told the ABC: “We determined is that nothing is being done anywhere in the world at the scale we're interested in."
However, researchers from Southern Cross University demonstrated in March the delivery system of the cloud-brightening system works by tracking the mist created 5 kilometers (3 miles) away and with a drone at cloud altitudes. They have not tested yet whether the system itself brightens clouds.
Other ideas involve making it easier for coral to establish itself, including installing frames, making natural surfaces more stable and adding chemical bonding agents. Some studies seek to give coral breathing space by controlling coral's natural enemies in the form of predators and seaweed.
Selective breeding of hardier coral varieties, particularly those from naturally warmer waters, is likely to make up a substantial portion of the effort, despite the risk that this will reduce diversity. The insertion of gene variations for heat tolerance into coral DNA is also under consideration, despite the inevitable resistance such an idea will face.
An 18-month study by 150 reef experts concluded interventions like these would double the chances of the GBR surviving to 2050 in good condition, but would only succeed if broader environmental changes were made.
Hardisty argued to the ABC these efforts are not a substitute for reductions in greenhouse gas emissions, instead being necessary to deal with the warming already baked in. However, since the Australian government is committed to greatly expanding fossil fuel production – some to be exported directly through the reef – the projects may be judged more about appearance than practical outcomes.
So far, Au$150 million (US$95 million) has been allocated by universities and the controversial Greater Barrier Reef Foundation for research over the next five years. Matching funds are being sought from the private sector. The cost of implementation of those ideas that prove viable will run to billions over decades, still cheap compared to the $6.4 billion a year the GBR provides in tourism and fishing alone.