Coral reefs ‘will be gone by end of the century’ – the first entire ecosystem to be destroyed by human activity.
In his book to be published on the 12th September 2011, ‘Our Dying Planet’ Professor Peter Sale says that coral reef ecosystems are very likely to disappear this century in what would be “a new first for mankind – the ‘extinction’ of an entire ecosystem”. Professor Sale has studied the Great Barrier Reef for 20 years at the University of Sydney and currently leads a team at the United Nations University Institute for Water, Environment and Health.
Coral reefs are on course to become the first ecosystem eliminated entirely from the Earth through human activity, something that will occur before the end of the present century, suggesting that there are children already born who will live to see a world without coral.
The predicted decline is mainly down to climate change and ocean acidification, though local activities such as over fishing, pollution and coastal development have also harmed the reefs. The book contains further predictions, such as the prospect that “we risk having no reefs that resemble those of today in as little as 30 or 40 more years”.
“We’re creating a situation where the organisms that make coral reefs are becoming so compromised by what we’re doing that many of them are going to be extinct, and the others are going to be very, very rare,” Professor Sale says. “Because of that, they aren’t going to be able to do the construction which leads to the phenomenon we call a reef. We’ve wiped out a lot of species over the years. This will be the first time we’ve actually eliminated an entire ecosystem.”
Coral reefs are important for their immense biodiversity, containing a quarter of all marine species, despite covering only 0.1 per cent of the world’s oceans by area, and are more diverse than the rainforests in terms of diversity per square kilometre and the number of different phyla* present.
*Phyla (plural) – Phylum: a major division of a biological kingdom, consisting of closely- related classes; represents a basic fundamental pattern of organization and, presumably, a common descent.
Research into coral reefs’ highly diverse and unique chemical composition has found many medically useful compounds that could be lost given the present trends, including new means of tackling cancer, a treatment for leukaemia derived from a reef-dwelling sponge, and even the possible application of compounds found in coral as a powerful sunblock.
Coral reefs have considerable economic importance to humanity; around 850 million people live within 100km of a reef, of which some 275 million, often the very poorest, dependant on the reef ecosystems for nutrition or livelihood. Reefs have great value as tourist destinations and also offer protection to low-lying islands and coastal regions from extreme weather, absorbing waves before they reach vulnerable populations.
Carbon emissions generated by human are the biggest cause of the rapid decline of coral reefs, affecting them in two ways.
- Climate change increases ocean surface temperatures, puts corals under enormous stress and leads to coral bleaching, where the symbiotic algae on which the reef-building creatures depend for energy disappear. Deprived of these for even a few weeks, the corals die.
- Roughly one-third of the extra carbon dioxide put into the atmosphere is absorbed through the ocean surface, leading to ocean acidification. This is a more recently recognised problem in tropical reef systems where the lower pH of the water makes it harder for reef organisms to build their calciferous skeletons.
The gaps between periods in which reefs are present have been long in geological terms, described in the book as “multimillion-year pauses”. There has been a tendency for reef disappearance to precede wider mass extinction events, offering a “canary in the environmental coal mine” for the present day, according to the author. “People have been talking about current biodiversity loss as the Holocene mass extinction, meaning that the losses of species that are occurring now are in every way equivalent to the mass extinctions of the past,” Professor Sale says. “I think there is every possibility that is what we are seeing.”
About 20 per cent of global coral reefs have already been lost during the last few decades. Mass bleaching events leading to widespread coral death are a relatively recent phenomenon; scientists have been studying coral reefs in earnest since the 1950s with mass bleaching being first observed in 1983. Dr Mark Spalding, of Nature Conservancy, and the University of Cambridge, who witnessed the catastrophic 1998 mass bleaching in the Indian Ocean first-hand, says: “It was a shocking wake-up call for the world of science, and a shocking wake-up for me to be actually there as we watched literally 80 to 90 per cent of all the corals die on the reefs of the Seychelles and other islands in a few weeks.” That single event destroyed 16 per cent of the world’s coral.
According to the book’s author: “The 1998 bleaching was spectacular because it was so extensive and so conspicuous. But there have been mass bleachings that have been global since then, 2005 was bad, and 2010* was bad. The visual appearance is not nearly as severe as it was in 1998, simply because there is less coral around.”
* See Reef Ramblings, ‘Global Bleaching 2010’.
Bleaching events coincide with weather patterns such as El Niño or shifts in the timing of the Monsoon season and are increasing in frequency owing to climate change. Tackling global warming is the most urgent solution advocated by the book. “If we can keep CO2 concentrations below 450 parts per million we would be able to save something resembling coral reefs,” Professor Sale says. “They wouldn’t be the coral reefs of the 1950s or 1960s, but they would be recognisably coral reefs, and they would function as reefs.” The current atmospheric carbon dioxide concentration is about 390 parts per million, but few experts believe it will remain below 500 for long.
Although there are signs that local conservation efforts can make a difference, with certain corals subject to low levels of stress being able to recover if pressures such as over fishing and pollution are removed, all this is really doing is buying time. If climate change continues at its current rate, they will be lost eventually.
Not all reef scientists agree with the timescales set out by the book, some would not be surprised if the demise of the reefs was to occur earlier, but they are in consensus.
“When you’re talking about the destruction of an entire ecosystem within one human generation, there might be some small differences in the details – it is a dramatic image and a dramatic statement,” says Alex Rogers, professor of conservation biology at Oxford University. “But the overall message we agree with. People are not taking on board the sheer speed of the changes we’re seeing.”
Click to read the first chapter of ‘Our Dying Planet’ by Peter Sale (University of California Press)
Based on an article by Andrew Marszal, published in the Independent on Sunday
Abbreviated and edited with additional information by Tim Hayes, Midland Reefs.