Question and debate Civil discourse lies at the heart of democracy and open debate is essential for science. Conferences and collections of papers, such as those in this issue, provide important means of facilitating our discourse. In them we can display our theories, findings, ideas, policies and practices in ways that encourage analysis, questioning and discussion. Is there new evidence? Did our theories hold up? Have circumstances changed? Have our policies worked well in practice? Reflection follows and we may find that we need to change or defend our ways. In doing so, we seek a better future, but may envisage it differently. What may be better for some may be worse for others. Some values are commonly agreed; others such as attitudes to nature, risk or property are not. Conferences and collections of papers are not arenas in which decisions are made; rather they are forums in which we can talk about changes and come to understand our differences and our agreements.