Defining reference conditions and restoration targets for lake ecosystems using palaeolimnology: a synthesis

The potential of palaeolimnological methods for establishing reference conditions and restoration targets for lakes has been recognised for some time, and has received renewed interest in recent years with the introduction of the EU Water Framework Directive. This paper considers some of the issues associated with the role of lake sediments in establishing reference conditions and defining recovery targets. We discuss the problem of attributing variation in the sediment record to human activity rather than to natural causes or random variability, and the need for the concepts of pristine and reference conditions to be differentiated. We address the question of expressing quantitatively the degree of change that has taken place between the reference and the present day and the problem of accounting for changes that may have taken place between the reference and the present, such as climate change, that may limit the use of the reference condition as a restoration target. Finally we consider the use of past habitat structure and inferred ecological functioning as targets for restoration, and the potential role that multi-proxy palaeoecological studies can play in defining such targets.