Carbon could kill reefs

Coral reefs could suffer severe structural damage and even death as a result of increasing ocean acidification brought on by rising carbon emissions, a new study has warned.

Published in the Journal Science 14 December, the study warned that in less than 50 years, oceans may be too acidic for coral reefs to grow. The acidification is a result of increasing carbon dioxide emissions, about one-third of which are absorbed by the world’s oceans.

Tim Austin, assistant director of the Department of Environment, said the report is important because it demonstrates that carbon emissions are making coral reefs sick, regardless of whether those emissions are causing climate change through global warming.

The report finds that carbon emissions are changing the chemistry of our waters. Although this changing ocean chemistry will affect different parts of the world in different ways, the report said that Caribbean reefs and Australia’s Great Barrier Reef will be among the most vulnerable to damage.

Mr. Austin said Caribbean reefs are more vulnerable because they are generally younger systems and are less diverse that reefs in other parts of the world. ‘The fact is our corals are not as adaptive; they do not have the gene pool to adapt as well,’ he explained.

The possible damage forecast in the report could have dire socio-economic impacts, particularly in the Caribbean, where dive tourism alone is estimated to generate more than $100 billion a year.

‘Under-resourced and developing countries have the lowest capacity to respond to climate change, but many have tourism as their sole income earner and thus are at risk economically if their coral reefs deteriorate,’ the report said. ‘For instance, tourism is a major foreign exchange earner in the Caribbean basin and in some countries accounts for up to half of the gross domestic product.’

The report warns that dying reefs could also have serious humanitarian implications, making coastal environments more vulnerable to storm and wave damage.

‘Reefs are really critical for protecting coastlines and keeping them stable,’ said Mr. Austin. ‘They play a huge role in quelling ocean swells. This can impact property; livelihood; the general way of doing life.’

Mr. Austin said the findings of the report are consistent with what the DoE has observed in a reef monitoring program it has been running at around 30 reef sites in the Cayman Islands for more than 10 years.

‘We are seeing a significant decrease in coral cover [throughout the Cayman Islands],’ he said.

‘What we have seen at [Cayman Brac’s] Bloody Bay is a rapid decline in coral cover between 1998 and 2000, most likely as a result of the world-wide bleaching episode that happened in 1998. Things then stabilized a bit, but there is still a general decline in coral cover.

‘We’ve seen a decline in coral cover from about 50 per cent down to about 15 per cent, which is consistent with other Caribbean losses,’ he continued.

‘The problem is that the declines here are taking place with reefs that aren’t exposed to some of the general stresses that reefs in places like Jamaica and other more populated, less developed places are exposed to.

‘Many corals in the Caribbean are living very close to their thermal tolerance right now.’

Local changes can help

DoE Director Gina Ebanks-Petrie acknowledged there is little the Cayman Islands can do to bring down global carbon emissions. But there are a number of steps these islands can take to reduce stress on local reefs, making them more capable of withstanding the effects of increasing acidification and warming ocean temperatures.

‘The suggestion here is that the less stress that is on a reef, the better equipped it is to deal with these larger stresses that are usually beyond our immediate control,’ she said.

What the DoE can have influence over is sedimentation, over-fishing, overuse of reefs and direct damage to reefs from vessel anchoring and other threats, she explained.

Mrs. Ebanks-Petrie said the Cayman Islands’ Marine Parks system, which was established in 1986, has done much to protect reefs around Cayman. But the initial effectiveness of that system may be leading to a false sense of security.

‘We’ve got to be responsive to the threats that are out there to our marine systems. Our Marine Parks system really doesn’t go far enough anymore; that is probably not a message that is well enough understood,’ she said.

‘I don’t think people in Cayman are aware just how delicate this situation is.

‘We need to be cognizant of the science and we need to be able to respond to it. We have to be aware of the increasing complexity of the threats that we face.’