Only one author in this volume elected to address the question of whether chaos is exhibited in the climate or ecosystem. We believe this is due to a number of rea sons. First, most investigators in climate and ecosystem sciences are unprepared to address the topic rigorously. Second, in many cases, the quantitative understanding of our systems is not yet advanced enough to apply large parts of chaos theory to LTER study sites.

We believe, however, that we should endeavor in future years to position ourselves to be able to apply chaos theory to our systems to discover new insights. Calls by the National Science Foundation for investigations into ecosystem complexity are consistent with this. Phillips (1999) has pointed to ways in which a qualitative analysis of partially specified dynamical Earth surface systems (ESS) can be made. In addition, virtually all that he says about ESS applies to ecosystems. We have mentioned previously, for example, that it is the very nature and definition of a chaotic system that small changes in initial conditions will often give rise to large changes in subsequent effects.

McHugh and Goodin are the sole authors who address the topic of chaos and complexity (chapter 11). Among other things they emphasize the large number of nonlinearities in the climate system. Other parts of LTER literature, such as the development of desertification theory at the Jornada LTER site (Scheslinger et al. 1990), suggest that nonlinearities are plentiful in our ecosystems. Sooner or later we will have to address the presence of nonlinearities, complexity, and chaos directly because these aspects are part of the real nature of our systems. We speculate that one or two decades from now a future LTER meeting on climate variability and ecosystem response will be couched in a framework of chaos theory.

We also note that ecosystem science is not alone in its failure to address chaos theory. Although Lorenz (1963) established a major part of the theory of chaos in atmospheric science, meteorologists have not pursued the theory with much vigor. On the other hand, Lorenz' discovery led to a paradigm shift in atmospheric science, which stemmed from the realization that because the atmospheric system was chaotic we could never hope to realize the dream of making a perfect weather forecast. We wonder what comparable paradigm shift, or shifts, await the field of ecology when we examine our systems with a focus on their nonlinear nature.

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