This book integrates decision-making and environmental science. For ecologists it will bridge the gap to economics. For practitioners in environmental economics and management it will be a major reference book. It probably contains the largest collection available of expressions and basic equations that are used in environmental sciences. Applying these expressions as 'rules-of-thumb' will give participants in a decision-making process a common platform for discussion and arbitration. To make the text comfortable to read, the book is organized in disciplines, but it also includes 13 applications that draw on all subjects in the book, and where cross-references are extensively used. The applications that range from siting of paper mills to wilderness management show how a range of topics in economics, social sciences and ecology are interrelated when decisions have to be made. The third chapter is called 'Getting started'. It shows how to carry out a complete environmental screening study in one day, much like the computer manuals that get you going from the first day. We believe that raising a platform for environmental decision-making puts issues into their right perspective, it is fun, and it lets an individual contribute to societys understanding of the environment in a very short while.