QUATERNARY CLIMATE AND MAMMALS IN THE PALEOLITHIC OF NORTHERN EUROPE: ECOLOGICAL NICHE MODELLING AND PALEOCLIMATIC RECONSTRUCTION

The climate envelope of a species describes the range of climate in which the species lives. The envelope is a multivariate space whose axes are climatic variables and whose boundaries are the maximum and minimum values of those variables. Climate envelopes have been used to predict the impact of future climate change on species distributions, and to analyze past distributions of species by projecting modern species distributions onto paleoclimate models, but in all cases climate envelopes have been used to study the distributions of single species relative to estimates of past or future climate models. We develop a new use for climate envelopes: to estimate paleoclimate from the joint distribution of the species found in association at a fossil site.

We used the full distribution of climate parameters across the range of a species to develop a statistical description of the climate associated with species that we applied to estimating the palaeoclimate of 22 British Quaternary sites associated with the ancient human occupation of northern Europe. We superimposed a grid on the modern geographic distribution of each species being analyzed, sampled the values of the climate variables at each point of the grid, and standardized them to obtain a multivariate joint probability distribution. The climate probability distributions of the species found at fossil sites were combined into a multivariate probability surface that gives the likelihood of climate given the species present at the site.

We found that climates reconstructed from their mammal faunas were reasonable compared to other palaeoclimate proxies. For example, the Gough’s Cave (MIS 2) was estimated to have a mean annual temperature of 5º C, an annual precipitation of 523 mm, and temperature seasonality similar to the coast of New Brunswick or western Alaska today. Examples where our estimates were grossly wrong appear to be due to the presence of large carnivores that today inhabit restricted environments due to the limitations of prey rather than climate.