Late last year the Australian Institute of Marine Science put out a rather scary report on the state of the Great Barrier Reef. It said the Reef has lost half its coral cover in the last 27 years! The loss was due to storm damage (48%), crown of thorns starfish (42%), and bleaching (10%).
Basically, the big storms are coming more frequently than the reef can absorb, higher water temperatures are causing widespread coral bleaching and rampaging swarms of crown of thorns starfish are eating up huge areas of coral.
The scientists connected with the report said that more frequent storms and higher water temperatures were connected to climate change and were therefore beyond the capacity of reef managers to do anything about (and the expectation is that these factors will only get worse).
Crown of thorns outbreaks, however, are believed to be connected to nutrient inflows from agriculture based on the mainland. And this was something they could act upon.
The situation presented here is one that conservation managers are facing everywhere: multiple stressors to the ecosystem but only some of them can be addressed because some operate at a scale beyond the reach of the manager. While it’s important to know the difference between what you can change and what you can’t, managers need to also appreciate how global stressors interact with local stressors. This information could be critical to how local action is carried out.
The risk of catastrophic events such as coral bleaching or cyclones are particularly challenging for conservation decision makers. Weighing up how a network of marine protected areas might best deal with these risks was the topic of earlier EDG research (see Decision Point #19).
De’ath G, KE Fabricius, H Sweatman & M Puotinen (2012). The 27– year decline of coral cover on the Great Barrier Reef and its causes. PNAS. http://www.pnas.org/content/early/2012/09/25/1208909109