The study is based on data from more than 2,000 surveys of 214 reefs between 1985 and 2012.
The findings showed an average level of decline of the coral cover of 0.53% a year and a total loss of 50.7% over the period of 27 years. The rate of decline has rapidly increased in recent years, averaging around 1.45% a year since 2006.
The alarming decline of the coral is partly the result of population explosions of the crown-of-thorns starfish, or Cots.
“When we say outbreaks, we mean explosions of Cots populations to a level where the numbers are so large that they end up eating upwards of 90% of a reef’s coral,” said John Gunn, chief executive of the Australian Institute of Marine Science, when interviewed by The Guardian. “Since 1962 there have been major outbreaks every 13-14 years.”
Other factors are tropical cyclones and coral bleaching.
The researchers are afraid that if the trend continued, the coral cover of the Great Barrier Reef could halve again within 10 years.
But there’s still hope. The reef is able to recover if given the chance, although very slowly. In the absence of storms, Cots and coral bleaching, the Great Barrier Reef can regrow at a rate of 2.85% a year, according to the scientists.
While cyclones and coral bleaching are related to longer-term challenges posed by climate change, the researchers have targeted the control of the starfish population as the quickest way to address regrow of the coral cover, which may lead to an increase of nearly 1% a year.
Source: The Guardian
Photo: Wikimedia Commons
De’atha, G, Fabriciusa, KE, Sweatmana, H, & Puotinenb, M (2012). The 27–year decline of coral cover on the Great Barrier Reef and its causes. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1208909109