[Coral-List] Coral trends on the Great Barrier Reef

[Douglas Fenner]

A new report is out on coral cover trends on the Great Barrier Reef.

A popular summary:  "Great Barrier Reef coral cover lowest in recorded
history"

http://seavoicenews.com/2018/06/08/great-barrier-reef-coral-cover-the-lowest-in-recorded-history/

The AIMS (Australian Institute of Marine Science) report:

https://www.aims.gov.au/reef-monitoring/gbr-condition-summary-2017-2018

open-access

Nice thing is the report shows the actual curves.  Looking at the graphs,
it is clear, as they say, that there has been coral cover lost in the last
couple years on all three sections of the reef (north, central, and south),
caused by different things.  As I look at the graphs, for the central and
southern sections, it looks to me like there has been a relatively small
downward trend over time since 1985, and present levels are within the
range of annual variation for those sections.  In the northern section
(where there are essentially no people or local human impacts), coral cover
didn't decline at all until about 2013 and has been in steep decline since
then (due to mass coral bleaching caused by hot water produced by global
warming and El Nino combined).  Further, losses from bleaching in 2017 are
not yet reflected in the graph, since that area hasn't been surveyed yet,
and one section farther south (Whitsundays) hasn't been surveyed yet and it
got hit by a cyclone.  So more decline in the curves appears to already be
build in.
      From the graphs in the report, it looks to me like the present
average coral cover of the entire GBR is little or no lower than in 2011,
due to a huge drop in coral in the southern section at that time.  If the
current level is the lowest for the whole GBR since AIMS monitoring began,
it is not by much.  So I think the headline of the popular article may not
really be correct.  But it is certainly currently one of the two lowest
coral cover periods in recorded history, both of which are in recent times,
and the trend is not good.
      On the hopeful side, some reefs like Scott Reef in NW Australia, and
Chagos in the Indian Ocean have recovered following even worse damage (in
1998) (as the southern GBR section did in the 2007 to 2015 period as seen
in the graph).  But more bleaching events are coming, probably more severe
and closer together.
      Plus, Chagos got hit by more mass bleaching in the last few years
that once again devastated those reefs, will it recover again?  Will the
northern GBR recover?  Or will they be hit again before they can recover??

      And other reefs are being pummeled as well:

99 percent of Japan's biggest coral reef is in jeopardy of being lost

http://seavoicenews.com/2018/05/18/99-percent-of-japans-biggest-coral-reef-is-in-jeopardy-of-being-lost/?mc_cid=edf0613c6b&mc_eid=8264f98e74

open-access

First report of a dramatic rapid loss of living coral on the north coast of
Western Samoa.

https://www.researchgate.net/publication/310480673

open-access

Zeigler et al.  2018.  Status of coral reefs of Upolu (Independent State of
Samoa)...  Marine Pollution Bulletin 129: 392-398.

check Google Scholar

Cheers,  Doug

-- 
Douglas Fenner
Contractor for NOAA NMFS Protected Species, and consultant
PO Box 7390
Pago Pago, American Samoa 96799  USA

New online open-access field guide to 300 coral species in Chagos, Indian
Ocean
http://chagosinformationportal.org/corals

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