A contribution to the history of forest clearance

Abstract

During the last five thousand years man’s activities have played an important and increasingly complex role in determining plant populations and habitats. His forest clearance and farming activities have long been recognized on pollen diagrams, usually by the presence of such pollen grains as those of cereals, plantain and other ruderals, and often, associated decreases in the tree pollen frequencies. However, the actual frequencies which change, and the amount by which they do so, varies from place to place and from time to time, and it is with this variation and its significance that we are here concerned. In general terms three basic questions must be asked about each example of human interference with the vegetation. First, exactly what is represented in terms of the changing plant communities, and why did they change? To answer this the successive changes in pollen frequencies must be very carefully defined by as close a sampling as possible. And there must also be a time scale for them, for knowledge of the time involved often becomes crucial for a fuller understanding of why the plant communities changed. Only a series of radiocarbon dates from each profile is really adequate for this purpose. Then, secondly, we want to know how large an area was being cleared and used. Was it just a few acres, or was it as much as a hundred square miles ? And finally, and perhaps most important of all, we want to know when these clearances occurred. Two places will not necessarily have the same history. Each area must be worked out separately before anything like a comprehensive picture can emerge for Britain as a whole.