It seems that when you look at the way the data was gathered, and find that while some areas of the GBR declined, others gained. Analysed other ways, it doesn’t seem so alarming.
Perhaps the phrase is “coral picking”?
Assessing loss of coral cover on the Great Barrier Reef: A response to Hughes et al. (2011)
H. Sweatman and C. Syms
Abstract
Hughes et al. (Coral Reefs, 2011, in press) challenge our interpretations of the changes in coral cover observed on the Great Barrier Reef (GBR) between 1986 and 2004 (Sweatman et al. in Coral Reefs 30:521–531, 2011). They question whether we can accurately assign all causes of coral loss; we contend that this makes no difference to the observed changes. They defend the validity of historical data on coral cover from before the start of systematic large-scale monitoring and conclude that coral cover has been declining since at least 1960, but we find no trend in the early data. We remain convinced that combining data collected at different spatial scales (quadrats and transects in the past mixed with more recent whole-reef averages from manta tows) are likely to overestimate decline, because whole-reef averages will very rarely reach the high cover values that can occur at the quadrat scale.
Hughes et al. (Coral Reefs, 2011, in press) state that we dismiss runoff as a cause of ecosystem degradation; we defend our interpretations and dispute some of their examples. In summary, we stand by our conclusion that coral cover on the GBR declined in the period 1986–2004 but through localised and unsynchronised changes that included recovery.
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My apologies to those commentators who are enduring these display half-done and poorly edited thought exercises
DJ Hawkins says
If you were within a few sun diameters of the surface of the sun a change in its diamter might have an effect on the orbital mechanics of a circling object with sun mass constant since you might get a few percentage points change in the near gravitational field gradient.
————
There is no “might” about this. You certainly will not get any percentage points change. This applies right down to the surface of the sun.
And you got cranked.
Andy Adkins’ reply, although weird, is earnest and probably heart-felt. However, I tend to ageee with John Marshall that the past tends to predict the future. Speaking as a Floridian who lives on a highly developed ancient coral reef, I tend to consider reefs as earthworks. Natural uprisings, tides and currents build earthworks that become habitats for plants, corals and other organism that in turn evolve a habitat ultimately upon which we’re growing orange or pecan trees and planning a trips to the Bahamas.
Here in Florida, though, we sink ships to make coral reefs. We’re fairly certain that any ship we sink will become a reef where well endowed ($$$) tourists may experience the wonders and hosing administered by the uneducated classes who fortuitously school themselves in the black arts of aquaculture, navigation and accounting.
The notion that the GREAT BARRIER REEF! could be in some way be eroded or impacted by something I DID through a contribution to GLOBAL WARMING is STUPID!
Even so, we are still doomed.
“Ric Werme says:
July 15, 2011 at 5:13 am
I first heard that the Great Barrier Reef was destroyed in the 1960s by being eaten by the Crown of Thorns seastar. (We called them starfish back then, but then someone realized that, by golly, they weren’t fish after all.) Perhaps someday my carbon footprint will become a carbon dioxide footprint, though I don’t know how to walk on CO2 unless it’s dry ice, and that sounds unhealthy.)”
FWIW: 🙂
Before returning to NZ I had my early schooling in OZ.
In the early 1970s we were taught told in school while in OZ. The Crown of Thorns starfish were eating the GBR alive and it was unlikely to be a coral reef left in 20yrs time. That conclusion BTW came from just one Marine biologist come activist!
I note that Andy Adkins reply to my post has disappeared. WUWT?
just another excuse for those cranberrians (Bob and Julia) to scream the sky if falling. Bob is also screaming the koala’s are dying and humans are responsible…… can someone tape his mouth shut please!
Andy Adkins says:
July 15, 2011 at 3:10 pm
My apologies to those commentators who are enduring these display half-done and poorly edited thought exercises
___________________________-
Thanks for finally remembering that we were discussing coral reefs, not interstellar physics. On a stylistic note: please edit your work with an eye toward avoiding anthropomorphic attribution as in “Earth attempts to compensate…”. The earth doesn’t think.
zooxanthellae don’t feed the corals, they supplement the corals while benefiting from the corals metabolic CO2 output. It is hard to conclude that elevated CO2 is killing algae that utilize it as food. Corals are nocturnal plankton feeders that hide from the heat and light of the day by contracting inside of their colonial exoskeletons. In these papers I never see any consideration for the fact that on a reef face where most of the corals live, the temperatures are vertically stratified. Temperatures also cycle diurnally. The temperature declines as you plunge into the deeper water. The corals peter out when there is not enough light to sustain the zooxanthellae. I have a hard time attributing bleaching to temperature. There are too many other independent variables that are more likely candidates.
Ferd Berple
Thanks for the reference. I can’t say I understood much of it, but clearly Zeebe is making a strong case that one way to reconcile a troublesome low SST for the Cretaceous period using O18/O16 ratio is to factor in a more acidic shallow seas (lower pH) resulting in heavier shells for various florsminifer – which presumably indicates a subsequent viable environment for many kinds of coral, etc. Please let me know if I have missed the point you were making with the reference.
Important bits considering the future of coral REEFS: even that corals have inhabit the Earth for millions of years, corals reef have not been the dominated form of reef structure for most of this time. Corals found in the GBR can live under warmer conditions (as in the Red Sea) but populations are adapted to their specific environment, corals in the GBR are not adapted to live in extremely warm environments. If it is the symbiont who is affected by temperature changes, the coral host, or both is still a matter of discussion, but nevertheless when it gets really hot in the GBR corals bleach and die. During 1998 calcification in inshore corals dropped to remarkably low levels and it took the corals 2-3 years to recover. Of course populations can adapt, but only if changes occur at a rate that allows the organisms to respond.
The threat for the GBR at the moment is mainly for inshore corals, and this where part of the confusion arises, mid-shelf and offshore reefs are doing some how well. When assessing the health of the GBR it is important to notice the difference cross-shelf and north to south differences. The GBR is a HUGE coral reef system that includes very different environmental settings and this should always be taken into consideration. In the inshore area there is an amplification of environmental changes (e.g. temperature variability) and added to this there is extra pressure from terrestrial run-off. Changes in the sediment and nutrient supply to the reef are probably the biggest threat. Furthermore when you have multiple stressors the tolerance level of an organism usually drops, so turbidity, eutrophycation, global warming and ocean acidification will probably synergistically, something that not necessarily has happened before in the GBR. Ocean acidification is a process that cannot be argued as it is simple chemistry, the impact on marine calcifiers is no clear but most experimental studies show negative changes in calcification, and apparently after a threshold level is crossed calcification stops. This could be similar to what is found with temperature, corals can only tolerate a range of temperature once values cross a thermal maximum calcification stops.
Apparently what is happening in the inshore is a community change, algae and phtyoplankton has become more dominant while coral cover and health has declined. The problem is that the degradation of the inshore are could progressively affect the mid-shelf and offshore area, as for example the carbon chemistry of the reef lagoon is very susceptible to biological driven changes. Furthermore if temperature continue to increase the thermal maximum for mid-shelf corals could be crossed and bleaching will become a problem in other reef areas not yet being affected.