Biodiversity in Herbaceous Semi-Natural Ecosystems
under Stress by Global Change Components

The BIOSTRESS project tested the response of semi-natural ecosystems in Europe to tropospheric ozone (O 3 ). O 3 is a highly phytotoxic trace gas and has been rising in concentration in remote areas roughly by a factor of five during the past 100 years due to human activity, i.e. emission of precursors such as nitrogen oxides, carbon monoxide and non-methane volatile organic compounds into the atmosphere. We combined both modelling and field experimentation work, employing different types of plant community growth models for experiments in virtual environments, and most recently developed field exposure systems for ozone fumigation in the real world where we used systems of different complexity – from two-species mixtures to species-rich systems with more than 40 higher plant species.

Major project outcomes:

We could clearly show effects of ozone on species interactions. We learnt that there are ‘memory' effects of vegetation for adverse effects of previous ozone exposure that are manifested months or even years afterwards. We also learnt that adverse ozone effects were more pronounced in more simple than in more complex systems as a general rule, suggesting that high biodiversity might make ecosystems less susceptible to ozone pollution. However, we would like to see more experimental evidence to confirm this suggestion. This finding makes us asking "How does biodiversity prevent adverse effects of pollution?" in addition to "How does pollution affect biodiversity?"

Besides the results that we gained on the response of semi-natural ecosystems to ozone, the BIOSTRESS project combined work on air pollution with biodiversity research involving basic ecological theories of plant functional types. By this means, we created modelling tools for experiments with virtual communities in virtual environments. These modelling tools can easily be used to assess the relationships between other environmental impacts and biodiversity since these tools are based on a sound theoretical framework. The adaptation of the modelling tools to assess the impacts of environmental conditions other than ozone would just require some few experimental work for model calibration.

Results from the project are being incorporated into the most recent updates of the UNECE Convention on Long-Range Transboundary Air Pollutants in order to derive critical levels for ozone pollution. It is clear that ozone pollution must be reduced – to prevent economic loss, to prevent adverse human health impacts, to prevent biodiversity loss – the target set by the Goteborg Council for 2010. The only way to do this is to reduce the emission of precursors for ozone formation from human combustion processes – most of it from vehicle traffic.

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