ECOLOGY/EVOLUTION

Life in a Field of Daisies

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Science  14 Jun 2002:
Vol. 296, Issue 5575, pp. 1933
DOI: 10.1126/science.296.5575.1933a

The sixth mass extinction in our planet's history appears imminent—precipitated, unlike the previous episodes, by human activity. To deepen our understanding of ecosystem resiliency and to explore how we might mitigate the effects of extinction are the aims of a collection of theoretical articles compiled by Solé and Levin. The main thrust of the argument is that ecosystems are complex adaptive systems that follow universal principles of organization.

James Lovelock propounded Gaia as a paradigm for the coupling between life and the physical environment of Earth, encompassing the biosphere. In their contribution, Lenton and van Oijen contend that Gaia may be the largest complex adaptive system in a hierachy that includes cells, organisms, populations, and ecosystems. They have added albedo mutation to the original Daisyworld model (of black and white daisies) for Gaia, and they show that variation and natural selection operate through feedback to dampen instability as adaptive behavior emerges. They also point out that, although the biosphere lies far from equilibrium and major events have suppressed biodiversity in the past, the system has always recovered without losing the capacity to capture free energy or to cycle elements. But this may be poor solace for humans facing the consequences of extinction. — CA

Philos. Trans. R. Soc. London B357, 617; 683 (2002).

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