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 abu ndance and quality are highest for recent time periods, but geological data provide a background to the understanding of present-day grazing-vegetatio n interactions. The Quaternary glaciations and recent anthropogenic influen ces have contributed to the loss of European mega-herbivores. The geologica l 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 con vert juniper scrub communities into open grassland at a regional scale. The balance between grazers and browsers has undergone continuous change durin g the last 10 000 yeats with significant consequences for forest compositio n and structure. Hunting statistics and archival records permit crude recon structions of population dynamics for certain ungulate species. High resolu tion pollen analysis and long-term monitoring generate reconstructions of v egetation that can be compared with fluctuating grazing pressure during the last few hundred years. Such data can be used to validate simulation model s of,grazing-vegetation interactions. (C) 1999 Elsevier Science B.V. All ri ghts reserved.