What does the future hold?

Internationally accepted projections of climate into the 21st century and beyond indicate a continuing rise in land and sea surface temperature caused both by existing greenhouse gas levels and by the continued rise in their concentrations. The rate of increase in temperature during this period is likely to be even greater than the increase observed during the 20th century. Elevated global surface temperatures and rising sea levels will continue for hundreds of years after stabilisation of greenhouse gas concentrations because of the long timescales on which the deep ocean adjusts to climate change. The success of international efforts to reduce and cap greenhouse emissions will determine the ultimate rise.

Some implications of the increasing rise in global temperatures are:

significant local variations in rainfall from historic records;
greater extremes in weather including more flooding, storm and cyclone events;
melting of ice in the northern hemisphere; and
a significant rise in sea level impacting coastlines and low-lying land.

The marine environment faces a long period, i.e. centuries, of water temperatures higher than present levels. The conditions that cause widespread coral bleaching globally were thought to happen once every few decades. It is predicted that the hot years, where the tolerance limits of the corals are exceeded, will be even hotter and more frequent.

Corals are already showing signs that they are approaching or exceeding their temperature tolerance limits. It is unlikely that any coral species will become globally extinct, although in the eastern Pacific Ocean some local extinctions have been reported as a result of bleaching. Some coral populations will probably survive in cooler areas within the reef. Coral larvae from tropical regions may be carried by ocean currents to suitable habitats at higher latitudes, where temperatures remain within their tolerance limits. However, after repeated coral bleaching mortality events, tropical coral reefs would be very different from the ones we know now.

What can be done?

The ultimate solution to protect coral reefs would be to target the source of global climate change, i.e. reduction of greenhouse gas emissions through reduced fossil fuel burning and increasing reforestation. The extent and rate of such changes are governed by complex political and socio-economic drivers and are unpredictable.

Continued research into the causes and consequences of global climate change is important. Accurate predictions of the geographic patterns and rates of change, and the best ways to respond to them, must be available to governments and the community. Sharing scientific resources is particularly important in addressing this global issue. Much research effort is also being focused on understanding the capacity of corals to adapt to warmer waters.

In the short-term, we must maintain coral reefs in the best possible condition. Reefs that are already stressed by environmental factors, such as poor water quality or overfishing, will be more vulnerable to changes in sea temperature. Conservative use of resources and liberal application of strategies to protect biological diversity, productivity and resilience are needed.

For human enterprises, such as tourism and fishing, surviving and thriving in the 21st century means:

working with scientists to determine the implications for different industries of projections of future environmental trends;
implementing best practices to protect the biological diversity, productivity and ecosystem processes that underpin their industries; and
working in the broader society to influence land-use, energy and population policies that may impact on their enterprises directly and through ecosystems.