A review of the mid-Holocene elm decline in the British Isles

Over the past 50 years the most enigmatic feature of pollen diagrams from northwest Europe has been the mid-Holocene ‘elm decline’, and there has been much speculation as to the origin(s) and cause(s) of this event. A total of 150 radiocarbon dates from 139 sites spanning the elm decline in Britain and Ireland have been collated and scrutinized. Statistical analyses on 138 dates show that the event has a mean date of 5036 14C yr BP with a standard deviation of ± 247. Calibration of the dates and combining the sum probabilities yielded a range spanning 6347-5281 cal yr BP (1s), covering 1066 years. The start of the elm decline event lies between 6343 and 6307 cal yr BP (1s), a period of 36 years, indicating that the onset was rapid. The end of the event lies between 5290 and 5420 cal yr BP (1s), a period of 130 years. The probability distribution indicates that the elm decline was a uniform phased event across the British Isles. It appears that the elm decline can be explained to a large extent by the outbreak of disease. However, recent research on palaeoclimatic change and the nature of the transition from the Mesolithic to Neolithic in the British Isles suggests that both climatic change and human activities were implicated. It was probably the interplay between these factors, rather than any in isolation, that catalyzed the widespread, catastrophic decline of elm populations during the mid-Holocene.