Coral reefs are dying at unprecedented rates. Rising water temperatures increase the frequency of mass bleaching events, ocean acidification makes it harder for corals to grow and maintain their skeletons and, since the 1980s, tropical coral reef coverage has declined by about 30 per cent to 50 per cent.
To combat this, a variety of ‘interventions’ are being developed by scientists across the world which could restore reefs. They vary enormously and include pre-exposure to warmer waters (a type of coral ‘vaccination’), shading of reefs, treatment with antibiotics and genetic modification.
A new report from the National Academies of Sciences, Engineering, and Medicine (NAS) has examined 23 of the most prominent of these resilience tools, determining which are ready to use (managed relocation of corals, for example) and which need more time and analysis (marine cloud brightening being one). The researchers behind the report have also developed a decision-making framework that can be used by policy makers and local communities to decide which intervention is most viable for their particular ecosystem.
Of the 23 interventions, Stephen Palumbi, who chaired the 12-member committee behind the report, points to the use of heat-resistant corals as the technique that currently has the most potential to be scaled-up. The process involves locating corals that are naturally more resistant to heat and then growing them in nurseries to later be planted or crossbred. ‘People find them all over the world,’ says Palumbi. ‘Even when there’s a natural bleaching event, there are corals that are bleached and right next to them are corals of the same species but in different colonies that are not. So that’s probably the intervention that is working best.’
Nevertheless, when it comes to protecting reefs, one size does not fit all. The key message of the report is that different tactics will work in different places. In particular, Palumbi notes that it’s essential to work with local groups. ‘Some communities might really want their corals restored because they want the fish,’ he says. ‘In that case you would restore the corals that protect and encourage fish. Another community might be looking at the waves rolling in and say “what we need is protection from wave action”. Still others might be doing their restoration in a place with rampant coral disease, in which case you would be much more sensitive to the danger of moving corals around and introducing new diseases.’
In the latter case, the potential dangers associated with moving corals raises the most fundamental point of all. Despite the wonders of innovation and science there remains no better way to protect reefs than to prevent their destruction in the first place. Scientists know that every intervention, however well-intentioned, could have consequences for the ecological balance of ecosystems. What’s more, no technique can protect corals indefinitely unless the ocean is protected. ‘These interventions are meant to help save corals for the next century while we get a grip on climate change,’ says Palumbi. ‘Without reducing emissions, without creating a world where CO2 is beginning to drop by the end of the century, corals don’t really stand a chance.’
This was published in the August 2019 edition of Geographical magazine
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