Do reefs have a future?
This was one of the questions that the 11th International Coral Reef Symposium (ICRS) aimed to answer. The 11th ICRS was held in Fort Lauderdale, Florida, USA on 7-11 of July 2008, as part of a chain of international meetings once every four years. About 2500 scientists, managers, and publics participated in this Olympic sized meeting; divided into 26 mini-symposiums to discuss 26 different aspects of coral reef, current issues and strategy for future reefs. Coral reefs are in crisis! Coral reefs face human and natural threats, including global warming, overfishing, coastal pollution, disease; and they are dying in alarming numbers these were some of the alarming messages given. Scientists estimated that 60% of coral reefs may disappear before 2050! According to these predictions the reefs seem to only have a short time on this planet as global warming will increase sea water temperatures by 1-20 C causing mass bleaching to corals and resulting in mass coral mortality. Some scientists believe in this 'doomsday' scenario that 100 years from now none of our grand children will see coral reefs in their natural habitat, and ironically it is because of us! Scientists and managers want the world to be aware of this, that we are facing a very serious problem.
The doomsday scenario
This is based on the idea that oceans are not able to absorb some of the carbon dioxide associated with greenhouse gas emissions, and it emerged the extra CO2was making the world's oceans more acidic, causing corals to crumble and deteriorate, and impeding new growth. Such a view would have it that coral reefs have reached the point of no return and that 500 parts per million of CO2 will occur within half a century - and when that happens, most reefs will die. The effect of CO2 on the global temperature will cause thermal stress, mass bleaching events, acidification of the oceans which reduce concentrations of calcium carbonate - the building blocks for the limestone skeletons that corals produce. The theory refutes the belief that coral reefs can adapt to the earth's changing climate, with evolution unable to keep pace with rapid shifts in ocean acidity and temperatures at 100 to 1,000 times faster than the Ice Age transitions. The proponents of the “doomsday scenario” say that evolution takes time, and what we are seeing “is a mismatch between the rate at which evolution can adapt to change, and the rate of change”. “Coral reefs can't keep up, and we're seeing an increased rate of coral degradation as a result, " says one of its proponents, Dr. Ove Hoegh-Guldberg from the University of Queensland, Australia.
The anti-doomsday scenario
In contrast, Professor Terry Hughes, the recipient of this year's Darwin Medal and head of the Centre of Excellence for Coral Reef Studies, James Cook University, Australia, gave a different viewpoint in his keynote address to the 11th International Coral Reef Symposium in Florida. Professor Hughes argued that the world's coral reefs are not doomed, provided that governments and communities take the urgent and necessary actions to preserve them. He claimed that our coral reef crisis was “a crisis in governance” , as we have identified the factors that are contributing to coral reef decline we now need proactive, forward looking governance that builds the resilience of coral reefs. In developing countries such as Indonesia this requires meaningful “bottom up” approaches to implement progressive fisheries regulations, reduce nutrient runoff and halt destructive practices. So the argument posed by this “progressive” perspective is that corals have the ability to bounce back, we cannot “climate proof” reefs but we can postpone by a few decades collapse due to overfishing and nutrients and in doing so build resilience. In the meantime governments around the world need to tackle the threat of climate that will limit rises in seawater temperature.
To support these arguments several studies have shown that coral reefs have the ability to adapt to water temperature rises or anomalies, but not all reefs have this ability. McClanahan et al. (2007) studied the impact of temperature variation on coral bleaching and mortality, and concluded that reefs that experienced high temperature variability tend to have higher ability to adapt and survive to temperature changes. These reefs may represent refugia where corals acclimate and adapt to environmental variation, which better prepares them for rising temperature and anomalies. Other studies showed for the first time that thermal tolerance in some corals have an underlying genetic component, suggesting a capacity to adapt to rising sea water temperatures. From a management point of view, these reefs should be selected as conservation priorities, targeted for management and further ecological research done in order to understand their acclimation, adaptation, and resilience to climate change.
Take home message
Its up to us - coral reefs may have a chance to survive global warming - but human help is required. NGO's, government and communities in developing countries are at the sharp end of these efforts.