1. NATIONAL ENVIRONMENTAL RESEARCH INSTUTE AARHUS UNIVERSITY 8 June 2010FAMILJ meeting in Stockholm Partitioning variations into ”natural” and anthropogenic variations? Jacob Carstensen Dept. of Marine Ecology National Environmental Research Institute Aarhus University

2. NATIONAL ENVIRONMENTAL RESEARCH INSTUTE AARHUS UNIVERSITY 8 June 2010 FAMILJ meeting in Stockholm Disentangling different sources of variation Natural perturbations Anthropogenic perturbations ECOSYSTEM Ecosystem indicators Error

3. NATIONAL ENVIRONMENTAL RESEARCH INSTUTE AARHUS UNIVERSITY 8 June 2010 FAMILJ meeting in Stockholm Factors operate at different time scales Meteorological conditions affect samples on the short time-scale (rain event, storms, calm periods, etc.) Human accidental episodes (oil spills, leaks from industrial plants, etc.) Seasonal variations give rise to cyclic patterns (light, temperature, and many other components associated with these) Anthropogenic processes are often linked to the seasonal variation (nutrient inputs, atmospheric emissions, etc.) Climate trends affect ecosystems (NAO, global warming, wind patterns, etc.) Long-term effects of anthropogenic activities (eutrophication, acidification, etc.)

4. NATIONAL ENVIRONMENTAL RESEARCH INSTUTE AARHUS UNIVERSITY 8 June 2010 FAMILJ meeting in Stockholm The BACI approach Control Impact Before After Natural perturbations only Natural and anthopogenic perturbations Relative differences will filter out the natural perturbations BACI = (IA - IB) – (CA - CB)

5. NATIONAL ENVIRONMENTAL RESEARCH INSTUTE AARHUS UNIVERSITY 8 June 2010 FAMILJ meeting in Stockholm BACI approach to time series Impact Control

6. NATIONAL ENVIRONMENTAL RESEARCH INSTUTE AARHUS UNIVERSITY 8 June 2010 FAMILJ meeting in Stockholm What if there are no control sites?

7. NATIONAL ENVIRONMENTAL RESEARCH INSTUTE AARHUS UNIVERSITY 8 June 2010 FAMILJ meeting in Stockholm A bit more sophisticated example: Macroalgae cover at stone reefs Estimated cover at a standard depth of 15 m

8. NATIONAL ENVIRONMENTAL RESEARCH INSTUTE AARHUS UNIVERSITY 8 June 2010 FAMILJ meeting in Stockholm A bit more sophisticated example: Macroalgae cover at stone reefs Estimated cover at a standard depth of 15 m

9. NATIONAL ENVIRONMENTAL RESEARCH INSTUTE AARHUS UNIVERSITY 8 June 2010 FAMILJ meeting in Stockholm Trend regressions

10. NATIONAL ENVIRONMENTAL RESEARCH INSTUTE AARHUS UNIVERSITY 8 June 2010 FAMILJ meeting in Stockholm Conclusions ›Natural and anthropogenic perturbations act on the ecosystem at different time scales (and spatial scales as well) ›Natural variations can be ”filtered out”, provided that there is a reference site unaffected by humans but similarly affected by natural variations ›If reference sites are not available, modelling is the only resort, e.g. by multiple regression analyses using natural and anthropogenic disturbances as input variables