How does rising atmospheric CO2 affect marine organisms?

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Increasing Climatic Variability
D'Odorico, P., Laio, F., Ridolfi, L. and Lerdau, M.T. 2008. Biodiversity enhancement induced by environmental noise. Journal of Theoretical Biology 255: 332-337.

What was done
The authors write that "recent climate change predictions indicate that, in addition to trends in the mean values of climate variables, an increase in interannual variability is expected to occur in the near future." Also noting that "environmental fluctuations are usually believed to play a 'destructive role' in ecosystem dynamics," they go on to explore the validity of this latter assumption within the context of current climate model predictions, asking themselves the question: "Can environmental variability have only 'negative' effects on ecosystem dynamics?"

What was learned
After lengthy mathematical analysis, D'Odorico et al. determined that "opportunities for species existence/coesistence are found to increase with 'moderate' values of the variance of environmental fluctuations, while they decrease when these fluctuations are relatively strong." This outcome constitutes what has come to be known as the "intermediate disturbance hypothesis," which grew out of the work of Connell (1978) -- who in the words of D'Odorico et al. suggested that "coral reefs and rain forests maintain high levels of diversity only in a non-equilibrium state" -- and Huston (1979), who noted that "most communities have relatively high levels of diversity because environmental variability maintains them in a non-equilibrium state."

What it means
Noting a number of real-world indications (Chapin et al., 1997; Steneck et al., 2002; Bengtsson et al., 2003; Elmqvist et al., 2003; Bellwood et al., 2004; Folke et al., 2004) that "biodiversity may enhance ecosystem resilience," the four researchers provide a theoretical basis for this phenomenon, demonstrating the validity of the ecological equivalent of the common dictum of physical exercise gurus: no pain, no gain. And in light of this exercise, it would appear that what many climate alarmists look upon as unfavorable may actually be just what is needed to (1) enhance the diversity and resilience of myriads of terrestrial and aquatic ecosystems, and (2) propel them to higher levels of activity in the brave new world of our CO2-enriched future.

Bellwood, D.R., Houghes, T.P., Folke, C. and Nystrom, M. 2004. Confronting the coral reef crisis. Nature 429: 827-833.

Bengtsson, J., Angelstam, P., Elmqvist, T., Emanuelsson, U., Folke, C., Ihse, M., Moberg, F. and Nystrom, M. 2003. Reserves, resilience and dynamic landscapes. Ambio 32: 389-396.

Chapin III, F.S., Walker, B.H., Hobbs, R.J., Hooper, D.U., Lawton, J.H., Sala, O.E. and Tilman, D. 1997. Biotic controls of the functioning of ecosystems. Science 277: 500-504.

Connell, J.H. 1978. Diversity in tropical rain forests and coral reefs: high diversity of trees and corals is maintained only in a non-equilibrium state. Science 199: 1302-1310.

Elmqvist, T., Folke, C., Nystrom, M., Peterson, G., Bengtsson, L., Walker, B. and Norberg, J. 2003. Response diversity and ecosystem resilience. Frontiers in Ecology and Environment 1: 488-494.

Folke, C., Carpenter, S., Walker, B., Scheffer, M., Elmqvist, T., Gunderson, L. and Holling, C.S. 2004. Regime shifts, resilience and biodiversity in ecosystem management. Annual Review of Ecology and Evolution Systems 35: 557-581.

Huston, M. 1979. A general hypothesis of species diversity. American Naturalist 113: 81-101.

Steneck, R.S., Graham, M.H., Bourque, B.J., Corbett, D., Erlandson, J.M., Estes, J.A. and Tegner, M.J. 2002. Kelp forest ecosystems: biodiversity, stability, resilience and future. Environmental Conservation 29: 436-459.

Reviewed 18 February 2009