Using historical plant surveys to track biodiversity on mountain summits

Background: Botanical records have been collected from mountain summits worldwide since the sixteenth century. Such records are of particular interest following the end of the Little Ice Age, when alpine climate changed. Aims: To review the evolution of alpine summit flora research and define appropriate re-surveys for documenting floristic changes since the mid-nineteenth century. Methods: The history of botanical observations of mountain summits worldwide conducted between the mid-sixteenth and mid-twentieth century is outlined. Secondly, we review evidence for floristic change on mountain summits from studies made between 1980 and 2010. Thirdly, we examine the methods used in earlier summit surveys and suggest appropriate approaches for reconducting such surveys. Results: We found ca. 300 summit flora studies up to 200 years old that are potentially suitable for re-surveying; most of them are in the Alps. Recent studies showed an increase in species numbers and an upward range extension of some species from lower elevations. For re-surveying it is judged best to carry out data collection by individual surveyors for sound comparisons with earlier studies. Conclusions: Data collected in historical summit flora studies allow their exploitation for long-term observation provided contemporary methods are replicated and the detection rate is estimated in the re-surveys.