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Impending Desertification Prevented by Termites?? How Is It Done?

Paper Reviewed
Bonachela, J.A., Pringle, R.M., Sheffer, E., Coverdale, T.C., Guyton, J.A., Caylor, K.K., Levin, S.A. and Tarnita, C.E. 2015. Termite mounds can increase the robustness of dryland ecosystems to climatic change. Science 347: 651-655.

Introducing their intriguing study, Bonachela et al. (2015) note that in arid and semi-arid savannas and grasslands, plants facilitate neighbors by increasing water infiltration while competing for water with distant individuals, citing Rietkerk et al. (2002). And they go on to say that "reducing rainfall generates a predictable sequence of patterns with decreasing overall plant biomass," going from over-dispersed gaps to "labyrinths, spots, and finally, barren desert," which last transition, in their words, "is known as a 'catastrophic shift,' or sudden collapse to an un-vegetated state," citing Rietkerk et al. (2004) and Scheffer et al. (2009).

In many arid ecosystems, however, they note that termite nests create substrate heterogeneity by altering soil properties and thereby "enhancing plant growth" and creating "islands of fertility (Sileshi et al., 2010)" that can serve as "refugia for plants and nuclei for re-vegetation," which phenomena can in turn "enhance drylands' resistance to and recovery from drought." And "by such engineering of soil," as they conclude in the final sentence of their paper, the six scientists state that "termites and other ecosystem engineers may buffer the effects of anthropogenic global change in some of the world's most environmentally and socioeconomically sensitive regions."

So what's the take-home message of these findings? Although we had never anticipated saying it, termites might be good for something!

References
Rietkerk, M., Boerlijst, M.C., van Langevelde, F., HelleRisLambers, R., van de Koppel, J., Kumar, L., Prins, H.H.T. and de Roos, A.M. 2002. Self-organization of vegetation in arid ecosystems. American Naturalist 160: 524-530.

Rietkerk, M., Dekker, S.C., de Ruiter, P.C. and van de Koppel, J. Self-organized patchiness and catastrophic shifts in ecosystems. 2004. Science 305: 1926-1929.

Scheffer, M., Bascompte, J., Brock, W.A., Brovkin, V., Carpenter, S.R., Dakos, V., Held, H., van Nes, E.H., Rietkerk, M. and Sugihara, G. 2009. Early-warning signals for critical transitions. Nature 461: 53-59.

Sileshi, G.W., Arshad, M.A., Konate, S. and Nkunika, P.O.Y. 2010. Termite-induced heterogeneity in African savanna vegetation: mechanisms and patterns. Journal of Vegetation Science 21: 923-937.

Posted 20 May 2015