Background
The authors write that "coral decline is frequently described as ongoing with the integrity and persistence of the reef system threatened by a number of different stressors," citing Bellwood et al. (2004); and they note, in this regard, that "climate change is widely regarded as the single greatest threat to coral reef ecosystems." Therefore, and further noting that "the scale and extent of bleaching on the GBR [Great Barrier Reef] since 1998 is unprecedented (Oliver et al., 2009)," and that "coral disease is an emerging stressor that was first recorded on the GBR in the early 1990s (Willis et al., 2004; Lough, 2007)," as well as the fact that various hurtful environmental disturbances "appear to be increasing in frequency and severity," they decided to quantify the trend in live coral cover of the GBR over the critical temporal interval of 1995-2009, which climate alarmists contend was the warmest decade and a half experienced by the planet to that point in time over the past millennium.

What was done
As part of the ongoing research of the Australian Institute of Marine Science, coral communities were surveyed annually between 1995 and 2009 on 47 reefs in six latitudinal sectors across 1300 km of the GBR, where between two and five reefs were surveyed in each sub-region. This was done at three sites on the north-east flank of each reef, where each site consisted of five 50-m transects marked by steel rods at depths between six and nine meters, and where "percent cover of live hard coral was estimated from a randomly selected sequence of images taken along the transects using a point-sampling technique in a quincunx pattern (Adbo et al., 2004)."

What was learned
The four researchers from the Australian Institute of Marine Science report that "coral cover increased in six sub-regions and decreased in seven sub-regions," with some of the changes "being very dynamic and others changing little." But with respect to the entire reef system, they report that "overall regional coral cover was stable (averaging 29% and ranging from 23% to 33% across years) with no net decline between 1995 and 2009." And to emphasize this fact, they forthrightly state that they found "no evidence of consistent, system-wide decline in coral cover since 1995."

What it means
In spite of all of the purportedly unprecedented negative influences arrayed against them over the past decade and a half, GBR corals appear to have held their own, maintaining a stable presence over the totality of their 1300-km linear expanse.

References
Adbo, D., Burgess, S., Coleman, G. and Osborne, K. 2004. Surveys of Benthic Reef Communities using Underwater Video. Australian Institute of Marine Science, Townsville, Australia.

Bellwood, D.R., Hughes, T.P., Folke, C. and Nystrom, M. 2004. Confronting the coral reef crisis. Nature 429: 827-833.

Lough, J. 2007. Climate and climate change on the Great Barrier Reef. In: Johnson, J.E. and Marshall, P.A. (Eds.) Climate Change and the Great Barrier Reef: A Vulnerability Assessment. Great Barrier Reef Marine Park Authority and the Australian Greenhouse Office, Department of the Environment and Water Resources, Townsville, Australia, pp. 15-50.

Oliver, J.K., Berkelmans, R. and Eakin, C.M. 2009. Coral bleaching in space and time. In: van Oppen, M.J.H. and Lough, J.M. (Eds.) Coral Bleaching: Patterns, Processes, Causes and Consequences. Springer, New York, New York, USA, pp. 21-39.

Willis, B.L., Page, C.A. and Dinsdale, E.A. 2004. Coral disease on the Great Barrier Reef. In: Rosenberg, E. and Loya, Y. (Eds.) Coral Health and Disease. Springer-Verlag, Berlin, Germany, pp. 69-104.