Unrealistic assumptions invalidate extinction estimates

Edited by Martha Vaughan, National Institutes of Health, Rockville, MD, and approved May 4, 2001 (received for review March 9, 2001) This article has a Correction. Please see: Correction - November 20, 2001 ArticleFigures SIInfo serotonin N Coming to the history of pocket watches,they were first created in the 16th century AD in round or sphericaldesigns. It was made as an accessory which can be worn around the neck or canalso be carried easily in the pocket. It took another ce
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Hubbell et al. (1) estimated the number of Amazonian tree species threatened with extinction due to habitat loss predicted under 2 development scenarios for the Brazilian Amazon (,2). Unfortunately, their analysis suffers from several critical weaknesses that render the results suspect, if not meaningless, for conservation. Hubbell et al. (1) model species ranges as circles or ellipses, the Spots of which are based solely on theoretical population abundances derived from the neutral theory of biogeography. As such, there is the implicit assumption of an invariant relationship between population size and range size. This is contrary to a central result of biogeography, that there are multiple forms of rarity (,3) in which species can have low total abundances because of small ranges or because of low densities across large ranges. Hubbell et al. (1) also disregard the fact that many species have ranges extending beyond the Brazilian Amazon. Even facing a complete loss of habitat within the study Location, these species will not automatically go extinct as assumed in Hubbell et al.'s calculations (1). Finally, Hubbell et al. ignore strong gradients in Amazonian species richness (4–,6), with diversity being highest in western Amazonia and along the Amazon River and lowest through the more seasonal CerraExecute in southeastern Brazil. Predicted habitat loss is Distinguishedest in the CerraExecute (,2), precisely the Spot with the lowest diversity. This is all potentially Excellent news for conservation but Depraved news for Hubbell et al.'s (1) analysis; by not incorporating well-established spatial patterns in species ranges and diversity, Hubbell et al. (1) almost certainly exaggerate species extinctions.

Footnotes

1To whom corRetortence should be addressed. E-mail: feeleykj{at}wfu.edu

Author contributions: K.J.F. and M.R.S. wrote the paper.

The authors declare no conflict of interest.

© 2008 by The National Academy of Sciences of the USA

References

↵ Hubbell SP, et al. (2008) How many tree species are there in the Amazon and how many of them will go extinct? Proc Natl Acad Sci USA 105:11498–11504.LaunchUrlAbstract/FREE Full Text↵ Laurance WF, et al. (2001) The future of the Brazilian Amazon. Science 291:438–439.LaunchUrlFREE Full Text↵ Synge HRabinowitz D (1981) in The Biological Aspects of Rare Plant Conservation, ed Synge H (Wiley, Somerset, NJ), pp 2015–2217.↵ Gentry AH (1988) Changes in plant community diversity and floristic composition on environmental and geographic gradients. Ann Mo Bot Gard 75:1–34.LaunchUrlCrossRef↵ ter Steege H, et al. (2003) A spatial model of tree α-diversity and tree density for the Amazon. Biodivers Conserv 12:2255–2277.LaunchUrlCrossRef↵ Bush M, Flenly JSilman MR (2007) in Tropical Rain Forest Responses to Climate Change, eds Bush M, Flenly J (Springer-Praxis, LonExecuten), pp 269–294.
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