[Coral-List] Biodiversity extinction (R.D.)

John Bruno jbruno at unc.edu
Sun Jan 31 21:44:39 EST 2010

Dear RD, I think these are good and fair questions. 

Absolute (global) species extinctions in the ocean have to date been quite rare (Dulvy 2003).  This could change, but I think a few other points are more germane to your questions.  First "biodiversity" is a broad (squishy) term that includes variation not just in species, but also in genes, genotypes, phenotypes, higher taxonomic levels, habitat types, ecosystems, etc (Stachowicz et al 2007).  So, you can and do see losses in "biodiversity" without species extinctions taking place.  Second, although global species extinctions are relatively rare in the ocean, local and functional extinctions are very common.  Such local extinctions, and other aspects of biodiversity loss, related to coral mortality/loss is fairly well-documented, especially for fish (e.g., see Jones et al 2004, Pratchett et al 2008).  And based on ecological theory and an enormous body of literature from other systems, the loss in structural heterogeneity caused by mass coral mortality will almost certainly drive large declines in most aspects of reef biodiversity.  Finally, the local extinctions that we are seeing on reefs and in many other marine ecosystems are primarily at higher trophic levels, causing a phenomena called trophic skewing (Duffy 2003, Byrnes et al 2007) which results in food webs dominated by lower trophic level species, with few large carnivores. 



Byrnes JE, Reynolds PL, Stachowicz JJ (2007) Invasions and extinctions reshape coastal marine food webs. PLoS ONE 2:e295
Duffy JE (2003) Biodiversity loss, trophic skew and ecosystem functioning. Ecology Letters 6:680-687
Dulvy NK, Sadovy Y, Reynolds JD (2003) Extinction vulnerability in marine
populations. Fish and Fisheries 4: 25–65.
Jones GP, McCormick MI, Srinivasan M, Eagle JV (2004) Coral decline threatens fish biodiversity in marine reserves. Proc Natl Acad Sci USA 101:8251-8253
Pratchett MS, Munday PL, Wilson SK, Graham NAJ, Cinner JE, Bellwood DR, Jones GP, Polunin NVC, McClanahan TR (2008) Effects of climate-induced coral bleaching on coral-reef fishes — ecological and economic consequences. In: Gibson RN, Atkinson RJA, Gordon JDM (eds) Oceanography and marine biology: an annual review, Vol 46. CRC Press, p 251-296
Stachowicz JJ, Bruno JF, Duffy JE (2007) Understanding the effects of marine biodiversity on communities and ecosystems. Annual Review of Ecology, Evolution, and Systematics 38:739-766

> Date: Fri, 29 Jan 2010 11:57:17 -0800 (PST)
> From: "R.D." <scubadivingdoc at yahoo.com>
> Subject: [Coral-List] Biodiversity extinction
> To: Coral-List at coral.aoml.noaa.gov
> Message-ID: <412224.94210.qm at web50906.mail.re2.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
> As a non-academic with field experience in coral conservation, coral disease, and marine park science and politics, I would like to comment on the recent Biodiversity extinction post, keeping in mind the "big picture".
> In the past few years several scientific biodiversity expeditions have reported in the lay press the discovery of thousands of new marine species from the Phillipines to Antartica to Australia to Tasmania to New Guinea and on and on. Such species have been scientifically collected, catalogued and classified. A Google search for "new marine species" yields a treasure trove of articles.
> On the other hand, an internet search for recently extinct marine species(especially credited to human influence) reveals sparse data. 
> Therefore, when a scientist speaks about "stopping the loss of biodiversity" and "continued biodiversity extinction" it seems incongruous to the reported facts. Is there scientific data to confirm this loss? Which species have been lost and how many? When we talk about habitat destruction, anthropogenic global warming, and overfishing, is there scientific data to confirm a "loss of biodiversity"? Or is it an assumption that it has happened or will happen?
> It is my understanding that environmental stressors rarely destroy an entire species(except for mass extinction events). In fact it is often environmental changes that allow new mutations to take hold and encourages the development of new species. As an example, a 2007 scientific survey of the Celebes Sea turned up between 50 and 100 new species of fish and invertebrates in an area that has been isolated by rising sea levels. 
> So my question is,"Is isolated habitat destruction on coral reefs really contributing to loss of biodiversity?" Is there scientific evidence?
> Or is the following analogy appropriate - If my entire neighborhood poisons all of the ant hills in our back yards, are we contributing to the loss of biodiversity? Will poison-resistant ants develop? Will different species of ants move in? Will the same species relocate from other areas? 
> I hate to see human induced damage to coral reefs as much as anyone. But loss of coral cover does not equal extinction of species.
> And if you are going to try to convince the general public otherwise, you will need to show them what species we have lost and how they have helped cause that loss. Because as of now, for every marine species put on the endangered list, there are hundreds or thousands newly discovered.

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