Using palaeoecological techniques to understand the impacts of past volcanic eruptions

Large volcanic eruptions may have major impacts on ecosystems through their physical, chemical and climatic affects. These impacts are stochastic and because the largest, most damaging volcanic events have not occurred in the recent past there is considerable interest in past eruptions as an analogue for possible future events. Palaeoecology is an essential tool to understand the environmental consequences of eruptions in the past. Here we review the processes by which volcanic eruptions affect ecosystems, how palaeoecological research can enhance our knowledge of palaeo-volcanic impacts and some of the challenges which such studies face. We focus particularly on tephropalaeoecological studies which address changes in the abundance of microfossils (e.g. pollen, diatoms, testate amoebae) across tephra layers preserved in sediments. In our discussion we stress the importance of impacts from volcanic tephra, volatiles and volcanically-induced climate change, which are likely to be the most spatially extensive impact mechanisms. We highlight the importance of considering the taphonomy of tephra and microfossils when attempting to identify volcanic impacts. We discuss the extent to which it is, and is not, possible to distinguish volcanic impacts from non-volcanic processes and random variability. The focus of this special issue is the Mediterranean and we conclude by discussing the particular issues which may apply in this region, including the availability of suitable archives and preservation conditions.