Coral reefs will be gone by the end of the century, according to a top UN Scientist. This would give coral reefs the dubious accolade of being the first entire ecosystem to have been destroyed by human activity.
Coral reef ecosystem
In the recently published book ‘Our Dying Planet‘, Professor Peter Sale writes that coral reef ecosystems are very likely to disappear by the end of this century, in what would be “a new first for mankind – the ‘extinction’ of an entire ecosystem”.
Sale, who leads a team at the United Nations University Institute for Water, Environment and Health, reports that the decline in coral reefs is mainly due to climate change and ocean acidification. Other activities, including overfishing, pollution and coastal development, have also had a devastating impact on the world’s coral reefs.
“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,” says Sale.
Acropora species on reef
The use of fossil fuels and the resulting carbon emissions, which contribute to climate change, are thought to be the biggest cause of the rapid decline in coral reefs. Climate change has led to increased ocean surface temperatures, putting reef species under enormous stress and leading to coral bleaching. Ocean acidification – caused by the oceans absorbing increased amounts of carbon dioxide from the atmosphere – is also an increasing threat, making it harder for reef organisms to retrieve the minerals needed to build their skeletons.
Although around 20% of coral reefs have already been lost in the past few decades, the authors of ‘Our Dying Planet’ are careful to stress that the corals themselves may well survive the effects of human activities and the destruction they cause.
“Although corals are ancient animals and have been around for hundreds of millions of years, there have been periods of reefs, and periods where there are no reefs,” explains Mark Spalding, of the US-based environmental group Nature Conservancy and the University of Cambridge. “When climatic conditions are right they build these fantastic structures, but when they’re not they wait in the wings, in little refuges, as a rather obscure invertebrate.”
A bacterial infection called white-band disease killed virtually all the dominant staghorn coral (Acropora cervicornis) on the reefs of Belize
Impact of natural disasters
It isn’t just human activities, however, that are impacting on coral reefs. In a recent study published in the journal Ecology, natural disasters, such as earthquakes and hurricanes, are also shown to have catastrophic impacts on reef ecosystems.
The study in Ecology looked at the after-effects of a 7.3 magnitude earthquake that shook the western Caribbean in May 2009.
Having been dominated by staghorn corals for nearly 4,000 years, the Belize reefs have lost their dominant corals due to disease and climate-induced bleaching in the last 25 years, drastically weakening the remaining reef.
As a result of the rapid and dramatic change to the coral reef assemblage, the earthquake in 2009 caused lagoonal reefs in Belize to avalanche and slide into deeper water, leaving behind only sediment and the skeletal debris of corals.
Lettuce coral (Agaricia tenuifolia) colonised the reefs in Belize after staghorn corals disappeared, but mass coral bleaching resulting from high temperatures during the 1998 El Nino–Southern Oscillation caused this species to also vanish.
Coral reefs are often considered the ‘rainforests of the sea’. Containing around a quarter of all marine species, coral reefs are hugely diverse, yet they cover just a small percentage of the world’s oceans. Not only are they important habitats for a variety of marine life, but they provide protection to shorelines, as well as contributing significantly to tourism and the fishing industry.
The highly diverse and unique chemical composition of coral reef ecosystems has also been found to contain many compounds that could be useful to the medical industry.
Conservation efforts crucial
According to Alex Rogers, a Professor of conservation biology at Oxford University, local conservation efforts can make a difference – but not forever.
“We know for certain that corals subject to low levels of stress are much more able to recover. So if you take away pressures like overfishing of coral reefs and pollution, this has profound effects on recovery. But what we’re really doing is buying time for many of these ecosystems. If climate change continues at its current rate, they will be done for eventually,” says Rogers.
Read the full article about the book ‘Our Dying Planet’ by Professor Peter Sale at the Independent.
Read the press release about the article published in the journal Ecology.
Find out more about corals on ARKive.
Helen Roddis, ARKive Species Text Author