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Biodiversity and the Multi-Functionality of Ecosystems
Volume 15, Number 15: 11 April 2012

In introducing their recent paper in Science, Maestre et al. (2012) note that many studies have revealed causal linkages between biodiversity and a number of different ecosystem services, which characteristic has come to be known as multifunctionality. However, they note that the relationship between biodiversity and multifuctionality had never before been assessed globally in natural ecosystems; and so they began the effort (and it's a big one) by reporting on what they discovered in a global empirical analysis that relates plant species richness and abiotic factors to multifunctionality in drylands, which ecosystems, in their words, "collectively cover 41% of earth's land surface and support over 38% of the human population"

When all was said and done, the study's fifty-three contributing authors (that's right, a whopping fifty-three) were able to report that "multifunctionality was positively and significantly related to species richness," and that "the best-fitting models accounted for over 55% of the variation in multifunctionality and always included species richness as a predictor variable." As a result, they concluded that the preservation of plant biodiversity is crucial to buffer negative effects of various phenomena that tend to further degrade drylands. And by inference, one could also conclude that the preservation of plant biodiversity should bode well for earth's other ecosystems as well.

To take maximum advantage of this discovery, however, one needs to peel back one more layer of the proverbial onion skin, as it were, in order to determine what it is that enhances the all-important biodiversity or species richness of ecosystems. And, fortunately, this task has already been accomplished - and some time ago at that - for in a study of the vascular plant diversity of fully 94 terrestrial ecosystems from every continent of the globe except Antarctica, the team of Scheiner and Rey-Benayas (1994) found that ecosystem species richness was more positively correlated with ecosystem productivity than it was with anything else. In addition, in a study of plant-animal interactions in 51 terrestrial ecosystems, McNaughton et al. (1989) found that the biomass of plant-eating animals was also an increasing function of aboveground primary production, while in a review of 22 aquatic ecosystems, Cyr and Pace (1993) likewise found that the herbivore biomass of watery habitats increased in the same manner with a rise in underwater vegetative productivity. Thus, the most basic and important question of all must be: What can drive the productivity of all ecosystems in an upward direction?

Peeling back yet another layer of the onion skin, the answer is seen to be an increase in the atmosphere's CO2 concentration, which enhances both plant photosynthetic prowess and (on land) plant water use efficiency; and these dual vegetative improvements invariably lead to greater overall ecosystem productivity. Yet even this more fundamental phenomenon is driven by a parent phenomenon at the core of the onion - anthropogenic CO2 emissions - which originate with mankind's burning of fossil fuels, such as coal, gas and oil, which activity thereby provides the ultimate elixir of life for all of the planet's carbon-based life forms ... including us!

Sherwood, Keith and Craig Idso

Cyr, H. and Pace, M.L. 1993. Magnitude and patterns of herbivory in aquatic and terrestrial ecosystems. Nature 361: 148-150.

Maestre, F.T., Quero, J.L., Gotelli, N.J., Escudero, A., Ochoa, V., Delgado-Baquerizo, M., Garcia-Gomez, M., Bowker, M.A., Soliveres, S., Escolar, C., Garcia-Palacios, P., Berdugo, M., Valencia, E., Gozalo, B., Gallardo, A., Aguilera, L., Arredondo, T., Blones, J., Boeken, B., Bran, D., Conceicao, A.A., Cabrera, O., Chaieb, M., Derak, M., Eldridge, D.J., Espinosa, C.I., Florentino, A., Gaitan, J., Gatica, M.G., Ghiloufi, W., Gomez-Gonzalez, S., Gutierrez, J.R., Hernandez, R.M., Huang, X., Huber-Sannwald, E., Jankju, M., Miriti, M., Monerris, J., Mau, R.L., Morici, E., Naseri, K., Ospina, A., Polo, V., Prina, A., Pucheta, E., Ramirez-Collantes, D.A., Romao, R., Tighe, M., Torres-Diaz, C., Val, J., Veiga, J.P., Wang, D. and Zaady, E. 2012. Plant species richness and ecosystem multifunctionality in global drylands. Science 335: 214-218.

McNaughton, S.J., Oesterheld, M., Frank, D.A. and Williams, K.J. 1989. Ecosystem level patterns of primary productivity and herbivory in terrestrial habitats. Nature 341: 142-144.

Scheiner, S.M. and Rey-Benayas, J.M. 1994. Global patterns of plant diversity. Evolution and Ecology 8: 331-347.