Estimating ozone risks using forest monitoring networks—results for science, policy and society

Key message: Few integration steps (adding low-cost ozone measurements, link to existing conventional monitors, joint data processing) transformed the traditional forest monitoring network into a multifunctional infrastructure producing information relevant for estimating risk to vegetation and human health. Context: Traditionally, forest monitoring networks have been designed to assess status and trends of forest condition. We argue that they can help providing answers to a much broader range of questions for science, policy, and society. Here, we concentrate on the example of ground-level ozone pollution. Aims: The aim of this study is to demonstrate the value of present forest monitoring networks as infrastructures that—with few integration steps—can provide important data and information to estimate the risk posed by ground-level ozone to vegetation and human health. Methods: We measured ozone concentration by passive samplers at the local (Trentino, northern Italy) plots of the ICP Forests Level I network over the period 2007–2011. By integrating these data with those from conventional ozone monitors (mostly located in urban areas), we (i) obtained an even distribution of air quality measurements over the investigated area, (ii) estimated international exposure indicators for vegetation and human population, and (iii) obtained data allowing geostatistical modeling and mapping of ozone concentrations, exposure, and associated potential risk. Results: Mean May–July ozone concentration ranged from 58 to 169 μgm−3, depending on forest site and year. Modeling and mapping (root-mean-square deviation (RMSD)= 12.31 μg m−3) provided evidence that the risk threshold for vegetation in terms of AOT40 was exceeded in large parts (90 %) of the study area, and frequently even by two times, depending on the year. With respect to population, up to 43% of the dwellers were exposed to medium–high risk of exceedances of the information threshold. Conclusion Ozone measurements carried out at the ICP Forests Level I forest monitoring network permitted mapping ozone levels and the estimation of possible risk for vegetation and human health. Forest monitoring networks can be seen as infrastructures that can be useful to address a wide range of environmental issues and with a much broader scope than their original on