Abstract
The aim of this paper is to highlight the uncertainties in planning development of ecologically sensitive areas (ESAs) and to analyse the types of knowledge relied on in most of the planning decisions about ESAs. Certain types of knowledge have been excluded from the formal planning system that includes both the policy - or decision-making authorities and the tribunals that test planning decisions. The Wanganui River minimum flows hearings are used as a case study to illustrate the obstacles to the integration of alternative knowledge with science as evidence in the formal planning system.