Novel climates, no-analog communities, and ecological surprises

Abstract

w ww ww w. .f fr ro on nt ti ie er rs si in ne ec co ol lo og gy y. .o or rg g H ow do you study an ecosystem no ecologist has ever seen? This is a problem for both paleoecologists and global-change ecologists, who seek to understand ecological systems for time periods outside the realm of modern observations. One group looks to the past and the other to the future, but both use our understanding of extant ecosystems and processes as a common starting point for scientific inference. This is familiar to paleoecologists as the principle of uniformitarianism (ie "the present is the key to the past"), whereby understanding modern processes aids interpretation of fossil records. Similarly, global-change ecologists apply a forward-projected form of uniformitarianism, using models based on present-day ecological patterns and processes to forecast ecological responses to future change. Thus, both paleoecology and global-change ecology are inextricably rooted in the current, and research into long-term ecological dynamics, past or future, is heavily conditioned by our current observations and personal experience.The further our explorations carry us from the present, the murkier our vision becomes. This is not just because fossil archives become sparser as we look deeper into the past, nor because the chains of future contingency become increasingly long. Rather, the further we move from the present, the more it becomes an inadequate model for past and future system behavior. The current state of the Earth system, and its constituent ecosystems, is just one of many possible states, and both past and future system states may differ fundamentally from the present. The more that environments, past or future, differ from the present, the more our understanding of ecological patterns and processes will be incomplete and the less accurately will our models predict key ecological phenomena such as species distributions, community composition, species interactions, and biogeochemicalprocess rates.Here, we focus on "no-analog" plant communities (Panel 1), their relationship to climate, and the challenges they pose to predictive ecological models. We briefly summarize a niche-based, conceptual framework explaining how no-analog communities arise (Jackson and Overpeck 2000). We discuss past no-analog communities, using the well documented late-glacial communities as a detailed case study (Jackson and Williams 2004), and argue that these communities were shaped by environmental conditions also without modern counterpart (Williams et al. 2001). We then turn to the future, identifying regions of the world at risk of developing future novel climates (Williams et al. 2007). Finally, we discuss the implications for global-change ecology, including the risk of future novel ecosystems (Hobbs et al. 2006) and the challenges posed for ecological forecasting. I In n a a n nu ut ts sh he el ll l: :• Many past ecological communities were compositionally unlike modern communities • The formation and dissolution of these past "no-analog" communit...

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“…Our ability to predict species' abundances and ranges, let alone how they will change, remains limited [18,22]. In order for biologists to predict how individual taxa and entire communities will respond to a changing world requires understanding why plant taxa grow where they do and what limits their ranges.…”

“…Applications are needed to perform exact and fuzzy matching of names, correct spelling errors, map synonymies and quantify taxonomic uncertainty. Existing applications such as TaxaMatch 11 and our own Taxon Scrubber 12 point the way to more sophisticated solutions (see 15,18]). In addition.…”

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“…These assemblages are called no-analogue communities (Ackerly, 2003;Williams & Jackson, 2007); their existence suggests that future climate change may produce combinations of species not previously experienced. New communities are appearing as species shift across landscapes tracking changing climates, and reflecting mixtures of native and alien elements; these novel assemblages represent communities for which details of their functioning has not been investigated.…”

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