The relative evaluation of wetlands for biological conservation has been the subject of many publication throughout the world during the last decade or so. A notable feature of these methodologies is their variability of approach. This variability is necessary to the extent that it reflects the diversity of wetland types, differences in information on wetlands and a variety of specific purposes for evaluation.
One purpose of this paper is to comment on other sources of variation between approaches – certain assumptions about the values of wetlands and the ways in which these can be assessed. Another purpose is to discuss several approaches to wetland evaluation in relation to the types of wetlands being considered and the advantages and problems of obtaining data on them. These subjects also provide an opportunity to reply to criticism of my own methodology for evaluation expressed by Gilligan (1984).