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Ecological and Environmental Change Research Group

4°C and beyond

Responses revealed in the fossil record for times when there was rapid temperature change and/or high CO2 levels and how these can inform future conservation strategies

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Kathy Willis, Shonil Bhagwat, John Birks, Keith Bennett

 

Of the many predictions for climate change in the coming century, a general consensus is that global temperatures will increase by 2-4°C and possibly beyond, sea-level will rise (~1 ± 0.5 m), and atmospheric CO2 will increase to 1000 ppmv. It has been widely suggested that the magnitude and rate of these changes will result in many (c. 35%) plants and animals going extinct, and there will be extensive die-back of tropical rainforests due to climate change. These worrying predictions are mainly based on models constructed using the present-day static distribution of species in relation to modern climate (Willis & Bhagwat 2009). Despite the limitations of these models, these predictions pervade the scientific and popular literature and highlight the dangers of future climate change to biodiversity and the oft-cited view that future climate change poses an equal or greater extinction threat to global biodiversity than land-use change and habitat loss.

Kathy Willis, John, Birks, and colleagues in Oxford and Belfast (Willis et al. 2010) have examined if there were comparable intervals of rapid rates of temperature change, sea-level rise, and/or high CO2 values in the past that can be used as analogues to assess possible biotic responses to future change, or are we really stepping into the great unknown. The palaeoecological record of fossil plants and animals at times when CO2 was up to 1200 ppmv (the Eocene Climate Optimum 51-53 million years ago), when temperatures at mid- to high-latitudes rose by 4°C in 60 years (NW Europe 11600 years ago), and when sea-level rose by up to 3 m higher than today (SE coast of Madagascar 2500-3000 years ago) provide valuable analogues.

Although the underlying mechanisms responsible for these past changes are very different from the causes of future change (natural processes rather than anthropogenic inputs), the rate and magnitude of climate change are similar to those predicted for the future and are thus potentially relevant to predicting future biotic responses. What the fossil records show is abundant evidence for rapid community turnover, species migrations, development of novel ecosystems, local extinctions, and shifts from one stable state to another. There is very little evidence for broad-scale extinctions due to a warming world. Based on the evidence from the palaeoecological record, Kathy Willis et al. present four recommendations for future climate-change integrated conservation strategies.

  • managing for novel ecosystems
  • retaining ecological memory
  • conserving regions of high genetic diversity
  • developing resilience to threshold events

These ideas focus less on preventing species declines and more on preserving ecological memory, ecosystem services and function, ecological processes, and evolutionary potential.

 

Key papers

Willis, K.J. & Bhagwat, S.A. 2009. Biodiversity and climate change. Science 326: 806-807. 10.1126/science.1178838

Willis, K.J., Bennett, K.D., Bhagwat, S.A. & Birks, H.J.B. 2010. 4°C and beyond: what did this mean for biodiversity in the past? Systematics and Biodiversity 8: 3-9. 10.1080/14772000903495833