Yorkshire Philosophical Society

Event Information

Peat bogs, climate change and prehistoric pyromania
Dr Jeff Blackford, Department of Geography, University of Manchester

The open moorlands of the British and Irish uplands, devoid of trees and dominated by heath species, are now considered valued heritage landscapes. Tree remains and preserved pollen records show, however, that large parts of the moorlands were previously forested, with climatic deterioration, peat growth and human impacts suggested as causes of deforestation. The talk will focus on the Mesolithic period, when pre-agricultural people are hypothesised to have created clearances to improve their hunting and foraging returns. The aim of this talk is to review recent research that tests these theories using independent measures of climate change in the past, excavation of tree remains buried in peat, and new fossil groups that demonstrate prehistoric burning and grazing.

Report
We tend to assume that open moorland, such as covers much of North Yorkshire, has always existed, but landscape has changed and evolved through human intervention as well as natural causes. Dr Blackford’s research on Bilsdale Moor demonstrated some of the changes that occurred in the Mesolithic period, between c11,000 and c5,500 years ago.    Peat deposits trap evidence of conditions at the time of deposition. Pollen indicates prevailing vegetation, insect remains vegetation and also animal activity, and tree stumps and other woody remains yield information about climate and other factors. A forested landscape emerges from the evidence, initially dominated by willow and poplar, giving way to pine, then oak, birch and alder. Pollen evidence indicates the sporadic appearance of open spaces towards the end of the Mesolithic, due possibly to changes in climate and soil conditions, or to deliberate human forest clearance by felling or fire. Insect remains imply large populations of animals which might open up and maintain forest clearings. Evidence of axe marks on tree stumps may indicate felling of timber for use, rather than deliberate clearance. Charcoal deposits may reflect human activity, or spontaneous fires during anomalous warm periods, when fires are more likely to happen.