Opinion
Fine-grain modeling of species’ response to climate change: holdouts, stepping-stones, and microrefugia

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Highlights

  • Understanding of microclimates may revolutionize climate change biology.

  • Microrefugia will be rare under future climate change.

  • Conservation strategies should focus on managing holdouts and stepping stones.

Microclimates have played a critical role in past species range shifts, suggesting that they could be important in biological response to future change. Terms are needed to discuss these future effects. We propose that populations occupying microclimates be referred to as holdouts, stepping stones and microrefugia. A holdout is a population that persists in a microclimate for a limited period of time under deteriorating climatic conditions. Stepping stones successively occupy microclimates in a way that facilitates species’ range shifts. Microrefugia refer to populations that persist in microclimates through a period of unfavorable climate. Because climate projections show that return to present climate is highly unlikely, conservation strategies need to be built around holdouts and stepping stones, rather than low-probability microrefugia.

Section snippets

A small revolution in climate-change biology

Mounting evidence from paleoecology suggests that small pockets of vegetation occupying microrefugia played a pivotal role in plant responses to rapid climate change during the transition from the Last Glacial Maximum (LGM) [1]. Pioneering work suggests that microclimates will have a similar role under future, human-induced climate change 2, 3. Modeled estimates of range shifts, population dynamics, and extinctions may all need to be reassessed in light of such fine-grain effects, with

Organism–environment interactions at fine scales

Environmental factors, including air and surface temperature, precipitation, radiation, and wind speed, interact with organismal phenotypes to create complex mosaics of temperature and water balance [6]. The interaction of multiple environmental factors can cause unexpected biotic responses to climate change, such as plants moving downhill in response to cold-air pooling [7]. Differences in microhabitat affinity can influence the strength of species interactions [8].

Environmental interactions

How do we talk about it?

‘Microrefugia’ is a term borrowed from paleoecology that describes isolated populations surviving in unusual microclimates relative to the surrounding landscape [19] or the places in which such populations persist [20]. As we describe below, the population-centered definition is more useful for analysis of the future. Such populations may help a species endure a period of unfavorable climate 19, 20, 21, or a glacial or interglacial climate excursion [1].

However, future climates are likely to be

What scale is appropriate?

Identifying holdouts, stepping-stones, and microrefugia requires models of future climate and models of biological response. Climate models are needed that can resolve microclimates capable of harboring small populations, areas as little as a few tens of square meters for insects and understory plants, to hundreds of square meters for dominant tree species. Biological models are needed to resolve the intersection of the environmental niche requirements of species with microclimates, the ability

Conservation consequences

Conservation planners need to be aware that microrefugia are unlikely under all but a few future climate scenarios, so that planning for holdouts and stepping-stones should be the major focus of protected areas and species plans. Continuing climate change produces fading holdouts, whereas climate reversal produces persistent microrefugia. All RCP scenarios project continuing climate change without reversal, except for a few RCP2.6 simulations (Figure 2). This indicates that microrefugia will be

What's next?

Next-generation models are emerging that can address the effects of dispersal, species interactions, population dynamics, and disturbance on holdouts and stepping-stones. LANDIS-II [50] and BioMove [51], for example, provide flexible, modular model architecture that allows users to vary spatial and temporal grain and extent and to select custom extensions to simulate a range of mechanistic detail, depending on the study objective. Climatic effects on fire regimes can be simulated, and species

Acknowledgement

We gratefully acknowledge funding support from the National Science Foundation Macrosystems Biology program NSF #EF 1065864 and the insights and comments of our collaborators in that project, Frank Davis, Janet Franklin, Alex Hall, Kelly Redmond, Alan Flint, Helen Regan, Lynn Sweet, and John Dingman. The work was also supported by NSF grant EF-1065638.

References (60)

  • S.Z. Dobrowski

    A climatic basis for microrefugia: the influence of terrain on climate

    Global Change Biol.

    (2011)
  • B.R. Broitman

    Predator–prey interactions under climate change: the importance of habitat vs body temperature

    Oikos

    (2009)
  • R.B. Huey

    Plants versus animals: do they deal with stress in different ways?

    Integr. Comp. Biol.

    (2002)
  • A.E. McKechnie et al.

    Climate change increases the likelihood of catastrophic avian mortality events during extreme heat waves

    Biol. Lett.

    (2009)
  • B. Helmuth

    Climate change and latitudinal patterns of intertidal thermal stress

    Science

    (2002)
  • K.A. Potter

    Microclimatic challenges in global change biology

    Global Change Biol.

    (2013)
  • S.A. Woodin

    Climate change, species distribution models, and physiological performance metrics: predicting when biogeographic models are likely to fail

    Ecol. Evol.

    (2013)
  • M. Kearney et al.

    Mechanistic niche modelling: combining physiological and spatial data to predict species’ ranges

    Ecol. Lett.

    (2009)
  • L.B. Buckley

    Can mechanism inform species’ distribution models?

    Ecol. Lett.

    (2010)
  • M.R. Kearney

    Biomechanics meets the ecological niche: the importance of temporal data resolution

    J. Exp. Biol.

    (2012)
  • M.B. Ashcroft

    Identifying refugia from climate change

    J. Biogeogr.

    (2010)
  • J. Elith

    Novel methods improve prediction of species’ distributions from occurrence data

    Ecography

    (2006)
  • N.A.S. Mosblech

    On metapopulations and microrefugia: palaeoecological insights

    J. Biogeogr.

    (2011)
  • V. Rull

    Microrefugia

    J. Biogeogr.

    (2009)
  • G. Keppel

    Refugia: identifying and understanding safe havens for biodiversity under climate change

    Global Ecol. Biogeogr.

    (2012)
  • A. Hampe et al.

    Conserving biodiversity under climate change: the rear edge matters

    Ecol. Lett.

    (2005)
  • K. Tabor et al.

    Globally downscaled climate projections for assessing the conservation impacts of climate change

    Ecol. Appl.

    (2010)
  • D. Scherrer et al.

    Infra-red thermometry of alpine landscapes challenges climatic warming projections

    Global Change Biol.

    (2010)
  • D.D. Ackerly

    The geography of climate change: implications for conservation biogeography

    Divers. Distrib.

    (2010)
  • J. Lenoir

    Local temperatures inferred from plant communities suggest strong spatial buffering of climate warming across Northern Europe

    Global Change Biol.

    (2013)
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