The palaeoecological approach to reconstructing former grazing-vegetation interactions

Interactions between grazing animals and vegetation are assessed from three temporal perspectives: millions, thousands and hundreds of years. Data abundance and quality are highest for recent time periods, but geological data provide a background to the understanding of present-day grazing-vegetation interactions. The Quaternary glaciations and recent anthropogenic influences have contributed to the loss of European mega-herbivores. The geological record from the Eemian interglacial in Denmark suggests that presence of elephant and rhinoceros did not create widespread openings in forest cover. Large populations of giant deer in ireland became extinct 11 000 years ago. We propose a theory that the giant deer were sufficiently abundant to convert juniper scrub communities into open grassland at a regional scale. The balance between grazers and browsers has undergone continuous change during the last 10 000 yeats with significant consequences for forest composition and structure. Hunting statistics and archival records permit crude reconstructions of population dynamics for certain ungulate species. High resolution pollen analysis and long-term monitoring generate reconstructions of vegetation that can be compared with fluctuating grazing pressure during the last few hundred years. Such data can be used to validate simulation models of,grazing-vegetation interactions. (C) 1999 Elsevier Science B.V. All rights reserved.