[Coral-List] We may keep the corals but lose the reefs

[Charles Birkeland]

I wish to call attention to a research paper that gives a good
demonstration of the current situation of coral reefs. I was not involved
in the paper in any way. It is by S. Yadav, T. Alcoverro, R. Arthur, “Coral
reefs respond to repeated ENSO events with increasing resistance but
reduced recovery capacities…”

http://link-springer-com-443.webvpn.jxutcm.edu.cn/article/10.1007%2Fs00338-018-1735-5

This paper reports on the tolerance or resistance and recovery of corals at
six sites in the Lakshadweep Archipelago to three ENSOs over 18 years. Even
though the harshness of the ENSOs increased, the coral survival or
resistance increased substantially. In contrast, there was a fourfold
decrease in rate of recovery. This is partly because disturbance is nearly
always faster than recovery, damaged or stressed corals tend to produce
fewer larvae because of energy limitations, reef community recovery times
become longer when fast-growing branching corals are more vulnerable to
stresses and disturbances and are replaced by more tolerant slow-growing
corals, disturbances become more frequent and do not allow sufficient time
for recovery, combinations of local and global disturbances and stresses
result in positive feedbacks that accelerate reef degradation, and degraded
reefs decrease the proportion of habitat acceptable to recruiting larvae.
In the recent past, many reefs had time to largely recover from events
before the next disturbance; otherwise the reefs at the sites would not
have developed as well as they had.  As those who go on liveaboard dive
ships know, there are still many splendid coral-reef communities that
display remarkably rapid recovery; but numerous surveys, including the one
recommended here, have indicated that average living coral cover is
decreasing circumtropically.  As disturbances increase in frequency,
recovery slows at the same time by the factors listed above working
together. I feel the biggest change during my career has been that
disturbances were events in the first decade or so, but events have been
evolving into trends of slower recovery, the reefs visited by liveaboards
becoming fewer exceptions. Prevention is more efficient and effective than
repair, despite corals becoming more resistant or tolerant.

In the case of this study, overfishing and algae were not problems,
nevertheless the reefs were deteriorating while the corals became more
tolerant. Possibly except for inexperienced corals that have originated
since the late Pliocene, the corals will probably not go extinct, but the
reefs will become functionally degraded. Ove Hoegh-Guldberg realized years
ago, “With all due respect to those contributing effort and funding towards
protecting coral reefs, the millions of dollars that are being spent will
be of no avail unless there is a concentrated effort to obtain explicit
progress in reducing CO2 emissions”.