global reef area

Mark.Spalding at Mark.Spalding at
Tue Feb 18 10:15:11 EST 1997

Thanks to Callum for his message on my behalf, I have in fact just got back 
from the Seychelles.  Our coral reef area paper is indeed "in press" in 
Coral Reefs, but attached is an abstract. I would agree with Bob Buddermeier's 
comments.  There is an enormous range in the area estimates produced by 
different authors much of which can be related to differences in definition.  
"Our" global area (255,000km2) focusses on the shallow areas of reef associated 
with the classic (Darwinian) reef-types. Largely due to lack of consistent 
mapped information around the globe we ignore the deeper submerged structures 
and areas of "reefal shelf".

I suspect that, even if we had all the information we could possibly want, we 
could expect global reef areas to vary by more than a factor of 10 simply due 
to very legitimate and useful variance in definition.

Best wishes

Mark D. Spalding                          E-mail: mark.spalding at
World Conservation Monitoring Centre
219 Huntingdon Rd
Cambridge, CB3 0DL                                     Fax: +44 1223 277136
United Kingdom                                         Tel: +44 1223 277314

M.D. Spalding and A.M. Grenfell. 
Global and regional coral reef area statistics are of considerable value in 
fields ranging from global environmental change to fisheries to conservation. 
Although widely quoted, Smith's (1978) figure of 600,000 km2 is only an 
approximate calculation. The World Conservation Monitoring Centre has prepared 
a new estimate of reef coverage by mapping emergent reef crest and very shallow 
reef systems. These data were rasterised, using 1 km grid squares, as a means 
of reducing errors arising from variation in scale. Global and regional reef 
coverages were calculated from the resultant grid. The total global area is 
estimated at 255,000 km2, considerably lower than many previous estimates. 
Variation in reef area estimates is, in part, a function of variation in reef 

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