Environmental policy is set in regard to both international protocols (e.g., the Kyoto Convention), directives (e.g., the European Union) and through national legislation. Environmental policy is implemented, monitored and decisions made concerning compliance and effectiveness by regulators (Environment Agencies). Industrialists may argue about the effect of any environmental legislation on their competitiveness, economists may debate the value of a sensitive ecosystem or plant species and which part of society should pay to maintain such an ecosystem or species, special interest groups lobby and publicise environmental issues while the public (as stakeholders) may be involved in public debate and consultation. Each group may present and debate the evidence (knowledge) as they see it, yet often the evidence base is incomplete and is subject to an often poorly quantified uncertainty. European Union environmental policy is based on the precautionary principle, covering situations where scientific evidence is insufficient, inconclusive or uncertain.
Statisticians have an important role to play in environmental decision-making, their contributions extend from the framing of environmental regulations and standards to reflect sound inferential procedures, to design and implementation of monitoring schemes and the analysis and quantification of environmental effects and policy effectiveness evaluation. Through several examples, we explore the quantitative and probabilistic nature of the language of policy, consider the evidence-base and discuss how statisticians can contribute to policy effectiveness evaluation before considering two case studies where statistical analysis is aiding the interpretation of environmental records and effectiveness evaluation. Copyright © 2007 John Wiley & Sons, Ltd.