[Coral-List] Evidence that ocean warming has caused most Caribbean coral loss
riskmj at mcmaster.ca
Thu Apr 27 12:35:31 EDT 2017
There is certainly little to disagree with in your statement. I take an even
more nuanced and pessimistic position-if it is indeed possible to be more
pessimistic than “looming extinction.”
Some years ago, I posted on this same list comments to the effect that sure,
global warming will put an end to coral reefs: but it really will only be
kicking over the edge of the cliff those poor sad remnants that remain after
we humans have messed with them.
We need to bear in mind that the world had already lost a lot of reefs,
perhaps more than half the original total, by the time climate change began
to ramp up. Yes, undoubtedly, we need to band together and speak with one
voice about reducing outputs of carbon dioxide. At the same time, I wonder:
where was that unanimity of purpose in the past, when the impacts of
land-based sources of pollution were obvious? Reef biologists chased after
various hypotheses-the reefs will come back if only the fish come back, or
if the urchins come back, or… while ignoring the gorilla in the room.
I do not really understand why this happened. Perhaps there was fear to
challenge vested interests; perhaps there was money to be made consulting
for developers and saying nutrients were unimportant; perhaps the trees of
individual careers were pursued inside the forest of gathering decline.
Perhaps the biologists who dominate this field were loath to tackle aspects
of chemistry and geology involved in pollution and sedimentation studies.
Those really interested in maintaining reefs need to bear in mind that there
have been (to the best of my always-incomplete knowledge) only two studies
on what happens to reefs if you improve the water quality: one Caribbean,
one Pacific. In both cases, the reefs improved. In neither case should this
have come as a surprise.
In short, I agree with you that we need a unified front, and my opinion is
that the need is all the greater because there was not a unified front 30
years ago. We have lost the opportunity to see how well truly unstressed
reefs respond to ocean warming. The news from the Northern GBR is truly
appalling-but as Charles says, recovery is another story.
I echo Charles’ sentiments, that we are conditioned by the reefs we have
seen. To me, a trip into the future was always epitomized by the transect
going from the outer Pulau Seribu (Thousand Islands) into the harbour at
Jakarta. One goes from lush coral islands (though severely over-fished),
past impoverished reefs, past some reefs that are now no more (see Tom
Tomascik’s poignant descriptions) and finally into an azoic sea-floor out of
the Archean. That’s what the future holds.
On Apr 26, 2017, at 11:41 AM, Steve Mussman <sealab at earthlink.net> wrote:
Dear John and Mike,
I ask this respectfully, don't you both (as well as the vast majority of
your colleagues) ultimately arrive at the same conclusion?
Correct me if I'm wrong, but regardless of how we got here, don't you agree
that it is ocean warming that now represents the consummate threat? I may
be interpreting things incorrectly, but It seems to me that at this point we
need a unified message reflecting the urgency of addressing this particular
At the same time we can all remain supportive of the various efforts aimed
at addressing local stressors.
Sent from my iPhone
On Apr 25, 2017, at 8:50 AM, Bruno, John <jbruno at unc.edu> wrote:
Dear Mike, thank you for your ongoing interest in this topic and my post.
"the Caribbean had already lost more than half its reefs before water
temperatures had increased by more than a fraction of a degree”
This is a common misconception from folks unaware that global warming began
many decades ago. Please have a look at the NOAA data plotted in this figure
from my post:
the graphics in Kuffner et al 2014 below it. These data should sort you out.
The Caribbean had clearly warmed significantly by the time mean coral cover
had been roughly halved (around the mid-1980s). Also, we haven’t lost any
reefs yet, what we’ve lost is coral cover (and fish biomass).
Iv’e dove near Havana and I agree - its a mess and was probably locally
impacted. And I don’t understand the logic in arguing managers should give
up because climate change has had significant impacts on corals. I’ve said
it a million times: local impacts need to be mitigated. We all agree on
that. I think you’re underestimating managers and local conservation
capacity. (All the managers I know acknowledge climate change but aren’t
giving up). As the Ocean Optimism symposium highlighted over the weekend,
local successes are realistic and very much meaningful and worthwhile.
"and there is overwhelming evidence of land-based stress going back to the
You have been promising this list-serv these references for years now. If
you ever find them, please do share with us if you have the time.
"how well could coral reefs survive ocean warming if they were not already
stressed by [local] human impacts?”
That experiment has been run dozens of times. On the northern GBR, on Scott
Reef, off Southern Cuba or in the Bahamas, across the central Pacific, etc.
The answer is not well at all.
The reason is that local impacts do not appear to act synergistically with
ocean warming. As Cote and Darling suggested
0438), the interaction appears to be antagonistic, not synergistic. Either
that or the impact of warming is so much stronger that it swamps the local
and synergistic signals. Also see Darling et al 2010: htt
1. mailto:sealab at earthlink.net
2. mailto:jbruno at unc.edu
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