New evidence has been published that the Great Barrier Reef is not in trouble from climate change. The effects of bleaching are short-lived and reversible. When I said this in my book, I was patronised from a great height by a bunch of marine biologists in New Scientist. Will they, and New Scientist, now apologise? As I keep saying, coral reefs are indeed under threat from man-made problems -- pollution, overfishing, run-off, but climate change is the least of their worries. Here's the abstract of Osborne et al's paper in PLOS One:
Coral reef ecosystems worldwide are under pressure from chronic and acute stressors that threaten their continued existence. Most obvious among changes to reefs is loss of hard coral cover, but a precise multi-scale estimate of coral cover dynamics for the Great Barrier Reef (GBR) is currently lacking. Monitoring data collected annually from fixed sites at 47 reefs across 1300 km of the GBR indicate that overall regional coral cover was stable (averaging 29% and ranging from 23% to 33% cover across years) with no net decline between 1995 and 2009. Subregional trends (10-100 km) in hard coral were diverse with some being very dynamic and others changing little. Coral cover increased in six subregions and decreased in seven subregions. Persistent decline of corals occurred in one subregion for hard coral and Acroporidae and in four subregions in non-Acroporidae families. Change in Acroporidae accounted for 68% of change in hard coral. Crown-of-thorns starfish (Acanthaster planci) outbreaks and storm damage were responsible for more coral loss during this period than either bleaching or disease despite two mass bleaching events and an increase in the incidence of coral disease. While the limited data for the GBR prior to the 1980's suggests that coral cover was higher than in our survey, we found no evidence of consistent, system-wide decline in coral cover since 1995. Instead, fluctuations in coral cover at subregional scales (10-100 km), driven mostly by changes in fast-growing Acroporidae, occurred as a result of localized disturbance events and subsequent recovery.
Here's what i wrote in my book.
Take coral reefs, which are suffering horribly from pollution, silt, nutrient runoff and fishing - especially the harvesting of herbivorous fishes that otherwise keep reefs clean of algae. Yet environmentalists commonly talk as if climate change is a far greater threat than these, and they are cranking up the apocalyptic statements just as they did wrongly about forests and acid rain. Charlie Veron, an Australian marine biologist: 'There is no hope of reefs surviving to even mid-century in any form that we now recognise.' Alex Rogers of the Zoological Society of London pledges 'an absolute guarantee of their annihilation'. No wiggle room there. It is true that rapidly heating the water by a few degrees can devastate reefs by 'bleaching' out the corals' symbiotic algae, as happened to many reefs in the especially warm El Niño year of 1998. But bleaching depends more on rate of change than absolute temperature. This must be true because nowhere on the planet, not even in the Persian Gulf where water temperatures reach 35C, is there a sea too warm for coral reefs. Lots of places are too cold for coral reefs - the Galapagos, for example. It is now clear that corals rebound quickly from bleaching episodes, repopulating dead reefs in just a few years, which is presumably how they survived the warming lurches at the end of the last ice age. It is also apparent from recent research that corals become more resilient the more they experience sudden warmings. Some reefs may yet die if the world warms rapidly in the twenty-first century, but others in cooler regions may expand. Local threats are far more immediate than climate change.