The Berne Symposium invited leading scientists of risk assessment research with transgenic crops on an international level in order to enhance the discussion regulators and members of the biotech industry. The goal was to determine the status quo and also to make progress in times of a first global spread of transgenes in agrosystems about risk assessment. The dialogue between scientists, regulators and industry representatives also revealed some lacunes of risk assessment research, which will have to be filled in the future: We still lack longterm experience, for which we will have to collect data with scientific precision. The symposium concluded asking for a risk-oriented longterm monitoring system based on critical science and hard data. This volume presents the discussion sessions as well as the scientific contributions and thus mirrors the risk assessment debate, based not on exaggerated negative scenarios but on critical science and hard data.

The present work was initiated in autumn 1991, with the aim to compile a catalogue of test methods useful for the risk assessment of transgenic plants, hereafter synonymously referred to as gene- tically modified plants (GMP). The steering group decided that the methods included in the catalogue should be based on recent litera- ture with the main emphasis on competition, establishment, and eco- system effects. The main user groups for the catalogue are scientists and students working in plant ecology and risk assessment and ad- ministrators with responsibility for the legislation of transgenic plants. A broad range of ecological and genetic methods in contem- porary use has been included in the catalogue. It is our hope that the present work will also be useful as a reference for experimental research in general plant population ecology and genetics. Most of the methods covered in the catalogue do indeed originate from these research fields. We would like to thank the members of the steering group, Hans Erik Svart and Smen Mark Jensen from the National Forest and Nature Agency, and Kaj Juhl Madsen from the Danish Environmen- tal Protection Agency for their support and assistance in initiating this work, and for valuable comments during its preparation. Several people gave highly valuable technical assistance: Lilian Mex- J0rgensen, Lone M0ller, Anna Marie Plejdrup, Karsten Rasmussen and Bodil Thestrup. Caroline Burke, Winnie Meilstrup, and Lone Th0gersen generously helped in correcting the language. Kathe M0gelvang is acknowledged for the drawing on the front cover.

The present work is a continuation of the work initiated in Autumn 1991, which resulted in the book, published by Birkhauser Verlag in 1994, entitled: Methods for Risk Assessment of Transgenic Plants. I. Competition, Establishment and Ecosystem Effects. Already when the work on volume 1 started, it was obvious to the authors, that not only the physical establishment of a transgenic plant outside the cultivated area was important for risk assessment, but also the possible gene-transfer from transgenic plants to other plants had to be considered. It was then decided to write a second volume on test methods, as a complement to the first, covering the main topics: Pollination, gene-transfer and population impacts. The main user groups for this volume are scientists and students working with plant population genetics and risk assessment and administrators with responsibility for legislation of transgenic plants. In order to cover such a broad range of topics, specialist knowledge was required. Therefore, colleagues in Denmark and Switzerland, working in these fields in relation to the concerns of using transgenic plants, were asked to participate. The result was a Danish-Swiss cooperation. A list of contributors to the book and their addresses is shown on p. VII. Financial support, which made the work possible, was given by: The National Environmental Research Institute, Denmark, the Federal Office of Environment, Forest and Landscape, Switzerland, the National Forest and Nature Agency, Denmark, the Danish Environmental Protection Agency and the European Commission, DC XI.