Interactions between climate change, natural ecosystems and disturbance regimes...

Interactions between climate change, natural ecosystems and disturbance regimes, and anthropogenic activities during the Holocene. A keynote lecture by Sandy Harrison held on Thursday 9 September, during 27th Annual Meeting of EAA Transformations of natural ecosystems by humans began with the shift from hunting and gathering to cultivation during the Mesolithic and Neolithic periods. These impacts increased as populations expanded during the Holocene up to the present day. However, the Holocene has also witnessed climate-driven changes in vegetation and in fire regimes, and these climate and environmental changes would necessarily have impacted the resource base for humans. It is important to be able to separate natural and anthropogenic influences on ecosystems and ecosystem disturbances at a regional level. Furthermore, while many factors underpin the growth and spread of agriculture, the role of climate and climate variability on the timing of the transition remains relatively unexplored. The degree to which anthropogenic changes in land use and land cover (LULC) during the pre-industrial Holocene affected global climate is controversial, and the impact of LULC changes on climate at a regional scale is also uncertain. Several recent developments make it possible to address these issues more systematically. New statistical tools have been developed that provide independent and robust quantitative reconstructions of past changes in climate, vegetation and fire regimes through the Holocene. These reconstructions can be compared with evidence for population growth and/or agricultural practices at a regional scale both to isolate human and natural impacts on ecosystems and disturbance regimes and to examine the potential impacts of climate and environmental changes on human activities. The development of process-based models provides an alternative way of examining climate impacts on natural vegetation and disturbance regimes, as well as on agriculture. Light-use efficiency (LUE) gross primary production models, for example, have been applied to simulate the impact of climate, climate variability, changes in atmospheric CO2 levels on vegetation, and of these environmental constraints and changing agricultural practices on agricultural yields through time. This talk will illustrate how various statistical and model-based approaches can and are being used to explore the interactions of climate, environment and people during the Holocene, focusing on ongoing work in the circum-Mediterranean region. It will also explore future opportunities to use these tools to address key questions of relevance to the archaeological community.