Charcoals from the Past: Cultural and Palaeoenvironmental Implications

It has been suggested that climates during the Holocene have varied on timescales of about 1500 years, forced by oscillations of a solar cycle. These climatic changes have been implicated as the cause of changes in geological records from, mostly, marine sediments. If there were such changes, and if they were of great enough amplitude to force changes in marine sedimentation, it would be reasonable to expect to see some changes in terrestrial environments. One record that is available across most terrestrial environments is the record of charcoal that results from the burning of vegetation. As burning might be expected to be more frequent under hot dry climates, this might react well to the climatic changes expected for maxima in the solar cycle, and thus provide a contrast to the reverse behaviour during solar minima. We examined eight records of microscopic charcoal from Europe and Australia, from temperate and more arid environments, using a range of statistical techniques to look for behaviour that might be caused by oscillating climates. None of the tests was positive. However, we did identify a range of behaviours indicative of specific structure in burning patterns (they are not random in time or intensity). Apart from an influence in some sites of late Holocene anthropogenic buring, there also appears to be little regional correlation in burning patters. We suggest that, for these eight records at least, burning events appear to be, on the whole, site-specific.