Areas under high ozone and nitrogen loads are spatially disjunct in Czech forests

It is widely accepted that excessive loads of nitrogen (N) deposition and ambient ozone (O₃) endanger natural ecosystems and the environment. Despite substantial reductions in emissions since the early 1990s both in the Czech Republic and in neighbouring countries, neither O₃ exposures nor N deposition have yet decreased to acceptable levels relative to the recommended thresholds. Based on long-term monitoring and high-quality data, we have indicated the areas of special risk due to high N deposition and O₃ exposures in Czech forests in 2000-2015. The areas of potential risk denote those forests under the highest loads of N deposition and O₃ exposure on a regular basis. The underlying classification approach is relativistic, i.e. based ultimately on quartiles of pollution intensities and not derived from critical limits or loads. The forest areas under the highest O₃ exposures and N deposition are spatially disjunct. The highest O₃ exposures are in the southern and the highest N deposition is in the northern Czech Republic. In contrast to our assumption, only 1322 km², i.e. 4.6% of the total forested area (28,782 km²) are overlapping areas with a potential risk due both to high O₃ exposures and to N deposition. Our results provide valuable input information for a more detailed environmental analysis, anticipated in the future, addressing to what extent the indicated areas at potential risk are associated with the actual negative impacts on forests.