The influence of climate change on the distribution of the Oak Processionary Moth in Bavaria

Abstract

The Oak Processionary Moth (OPM) is a heat-loving moth native to the warmer regions of southern Europe, with an increasing range in central Europe. Its caterpillars, living in gregarious aggregations, can cause defoliation of infested trees. The OPM is of particular concern. Stinging hairs of its caterpillars can cause allergic reactions through the skin and respiratory tract. The hypothesis being discussed is that increasing warming caused by climate change favours the spread of thermophilic moths. The study is geographically focused on the Free State of Bavaria/Germany, where the pest first became known in the 1990s. Bavaria's natural forest communities historically contain a high proportion of broadleaved oaks. Because oaks thrive in warm, dry forest landscapes, they are in suspicion promoting the distribution of the OPM. Beside oaks are hosting the OPM, they offer hope for climate-adapted forest conversion because of their good climate resilience. The hypothesis is tested through a systematic study of the habitat characteristics of OPM habitats by matching factors influencing population dynamics with time series of geographically referenced population data. The analysis precedes an extensive literature review and uses OPM population and climate science time series. The results provide fitting data to support the hypothesis. Population dynamics show a high correlation with climate warming parameters, but global warming is not the only factor. The implications for OPM population trends summarise and complement the current state of knowledge and provide a strong rationale for more in-depth research into scenarios for future population trends using geo-databased climate projections, forest history, site and silvicultural data to provide a assured assessment for the long-term success of the 'oak tree' under the threat of increasing infestation by the Oak Processionary Moth.