[Coral-List] Coral range expansion with global warming

Thomas Goreau goreau at bestweb.net
Sun Jan 13 20:45:35 EST 2008

Dear Allen,

I don't have references handy, but here are some leads.

With regard to range expansion:

Mexican researchers have been following northward expansion of corals  
in the Sea of Cortez for some years, and I hope they can point to  
papers on this. Surveys at Sodwana reef in South Africa show that  
live coral cover and diversity have been steadily increasing. It  
would be most interesting to see if the corals are expanding  
northward on Honshu, Japan, and there may be studies on this by  
Japanese researchers. Australia should be seeing the same.

In SE Florida the local dive groups I work with there, Cry of the  
Water in Broward County, and Reef Rescue in Palm Beach County, are  
seeing expansion of the now rare Acropora cervicornis and Acropora  
palmata northwards. But they are severely threatened by dredging  
projects and algal blooms around the offshore sewage outfalls, which  
we have now finally convinced the Governor, after years of appeals,  
to shut down.  If we can get these reefs protected (which they are  
not now),  clean up the water, and stop the new dredging projects,  
which killed almost all the live reefs of the area in the 1960s and  
1970s, we should see significant northward coral expansion since  
there is a good supply of coral and fish larvae swept out of the  
Caribbean by the Gulf Stream.

Thanks to above average sea surface temperature rise, the  
Mediterranean is now warm enough for reef building corals, but the  
two local species with zooxanthellae don't build up large  
aggregations, and there would be reluctance to introducing non-native  
species. However, a few million years ago the Mediterranean area was  
the global center of coral diversity.

But dreams of coral reef marching poleward, which have been proposed  
by some in the past as a benefit of global warming, are probably  
fiction. The reason is that the coastal areas of North America, Asia,  
and Australia that they could expand to are densely populated and the  
sewage and agricultural nutrients are way too high for coral reefs  
even if the temperatures were acceptable.

With regard to the time it takes to form framework coral reef  
structures that creates sheltered habitats, as opposed to coral reef  
communities that are sparse veneers on non growing coral substrate,  
that can take a long time since reefs (as opposed to corals)   
typically grow millimeters a year.

Best wishes,

On Jan 13, 2008, at 7:15 PM, Allen Chen wrote:

> Hi, Thomas
> In your e-mail you have stated " There is clear evidence of
>> corals expanding into warmer water at the limits of their ranges, but
>> this results in coral communities, not coral reefs, which take
>> centuries to thousands of years to develop. Even if the corals could
>> adapt to warmer temperatures, and there seems to be no really good
>> evidence that they can on the time scale that would be needed, the
>> existing reefs would die quickly, and it could take thousands of
>> years for new reefs to be established."
> This is an interesting observation. I am wondering you can provide  
> the list of references that we can read?
> thank you in advance.
> Cheers, Allen

Thomas J. Goreau, PhD
Global Coral Reef Alliance
37 Pleasant Street, Cambridge MA 02139
goreau at bestweb.net

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