Jennifer Marohasy
Follow The latest report of the Australian Institute of Marine Science, has a record coral cover at the Great Barrier Reef. However, this figure is 30% lower in about half of the coral reefs surveyed.
The relatively low coverage rate is due to the fact that only the reef circumference was surveyed by AIMS, which is comparable to that reported by Sydney’s population after circling the outer suburbs.
Such a method (surrounding suburbs) would not show population trends in more densely populated inner-city areas. And so the latest AIMS report gives no indication of coral cover at the reef crests, but for all we know based on the methodology that underlies the survey. This latest, may have completely collapsed on the Great Barrier Reef.
We cannot know.
Furthermore, despite advances in both underwater and aerial mapping, which can provide automated quantitative assessments of habitats with visual and/or visual recordings, AIMS persists. with a method that involves dragging an observer to track the coral.
Their methods are subjective and classical. It is not science.
My early career was as a field biologist in Africa. If I had submitted the AIMS survey as the expected survey method for any one of the many insect species I track, my supervisors would have rejected it. Whether trying to track changes in the population of an insect, the number of people in a city, or the hard coral cover of the Great Barrier Reef, there are certain factors that need to be considered if the method is to be used. This method is considered scientific and therefore reliable. .
Major deficiencies in the current AIMS long-term monitoring program include:
1. Conclusions are made about overall coral cover at each reef without measuring coral cover in key habitats (eg at the top of the reef).
2. The change in coral cover is never quantified by habitat type (eg: reef crest versus posterior lagoon).
3. The survey area at each reef (defined by AIMS as the total ‘reef circumference’ as measured by the total number of mantises) incorporates results from different habitats, and therefore, it is suspected that the sample plan is appropriate in terms of the number of repetitions (manta tows) per treatment (habit) at each reef perimeter.
4. Numeric values represent subjective guesses.
5. There are no images or video recordings that allow quantification of the accuracy of the guesses.
If we take John Brewer Reef as an example, most healthy corals grow on top of the reef, where it exceeds 100% of cover in many places. Coral at the top of the reef grows on a solid limestone base that is made up of layers, layers of dead coral. This reef crest is about 9 meters above the reef circumference in the northern lagoon, where coral grows among the rubble and sand with a much thicker coral cover. Because the AIMS long-term monitoring program only surveyed the perimeter, it determined the coral cover at this reef to be 22%. To be clear, there could be a large mortality rate for the apex coral, where most coral species are located, but this will never show up in the long-term monitoring results for the Reef. John Brewer.
I have shown the potential of an alternative method at Pixie Reef that places 10-meter image clippings (instead of mantis) that are repeated (replicated) at least 9 times (to allow quantification of changes in the environment). habitats) for three different habitat types (crest, posterior lagoon, and anterior reef).
Photos from these cross-sections and more information on the method, are available at my Pixie Reef 2021 data page, here: https://jennifermarohasy.com/coralreefs/pixie2021/
Fundamental to the success of any survey designed to detect change, must be a consideration of the distribution of populations of interest (e.g. corals by habitat or people by habitat). suburbs) before trying to quantify it – to count it. Only then can one know with any degree of certainty if there are any significant changes in the overall population of the city or the reef and/or some of its composition.
It is unfortunate that AIMS has wasted a lot of time, money and diesel over the years, at the expense of Australian taxpayers, without any discussion or explanation of this approach. Most people interested in the results assume that all important habitats have been surveyed, but that is not the case. They assume that corals are indeed counted, but that is not the case.
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The featured image at the top of this blog post is a drone shot of Pixie Reef looking from the back lagoon over the top of the reef to the front of the reef being subjected to prevailing winds . Coral cover and species diversity vary considerably with habitat.
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