Epiphytes lichen in the change of immissions and climate • Results of a comparison mapping 1989/2007 in north Germany

Epiphytic lichens as indicators for changes in air pollution and climate. Results of a comparative survey 1989/2007 in north-west GermanyBackground, aim, and scope Lichens growing on tree bark (epiphytic lichens) respond very sensitively to environmental effects such as chemical substances and air temperature. Therefore, they are used as biomonitors for atmospheric pollution in environmental assessments. Based on a survey of epiphytic lichens in 1989, a repetition was performed in an intensively-used agricultural area of north-west Germany in 2007. The objective of this study was to assess possible changes in air pollution and climate.Materials and methods The study is based on a comparative inventory of epiphytic lichens, growing on 335 trees at 45 monitoring sites. A simplified half quantitative survey technique of the first survey was used.Results Indeed, major changes to the epiphytic lichen flora were found. Overall, nearly all monitoring points showed an increase in the level of lichen species. A sharp decrease in acidophileous species and a sharp increase in basidophileous and nitrophileous species were detected. In addition, an increase in thermophileous species which are mainly inhabitants of southern European countries was observed, combined with decreases in boreo-montanic species.Discussion These trends correspond with supra-regional observations. They are primarily attributed to changes in air pollution involving a decrease in SO₂ and an increase in NH₃ concentrations. Clear effects from climate change are evident as well.Conclusions Changes to epiphytic lichens over a 18-year period could be demonstrated using a relatively low-cost investigation. They are relevant for assessing the changing environmental situation, which is of great importance for other organism groups and ecosystems.Recommendations and perspectives Using standardized techniques epiphytic lichens are suitable bioindicators for obtaining different types of information about the air pollution in urban areas and in intensively-used agricultural regions. Furthermore they are obviously good indicators of temperature changes in their environment. More research is needed about the suitability of epiphytic lichens for a biomonitoring of climate changes.