TEXTE ENVIRONMENTAL RESEARCH OF THE FEDERAL MINISTRY OF THE ENVIRONMENT, NATURE CONSERVATION AND NUCLEAR SAFETY by

Publications by the Federal Environmental Agency in the TEXTE series are available subject to advance payment of 7,50 Euro by bank transfer, crossed cheque or paying-in form to At the same time please direct your written order to the Firma Werbung und Vertrieb naming the volume number from the TEXTE series, and the name and address of the orderer. The publisher does not accept responsibility for the correctness, accuracy or completeness of the information, or for the observance of the private rights of third parties. The contents of this publication do not necessarily reflect the official opinions. Acknowledgements We like to thank Dorett Berger (ZALF, Müncheberg) for supporting the project with literature search and technical help, Claudia Schultz for data mining and contributing a figure for the text and Nina Mitra (both: FSP BIOGUM, University of Hamburg) for technical help. We are also greatful to Petra Apel and Ingrid Nöh (Federal Environmental Agency, Berlin) and also to Hanka Teichmann (German Federal Agency for Nature Conservation, Bonn) who coordinated and assisted the study and the process in a very professional and supporting way. Volker Beusmann (FSP BIOGUM, Head of the agriculture group) provided the frame, which made it possible to finish the project under the high pressure of a deadline. Last but not least we want to thank all experts, who responded to our questionnaire and who all sent very helpful comments on the draft. Summary 68 References 76 Appendix 92 2