Indicator quality for assessment of impact of multidisciplinary systems

Since environmental conservation has provoked much interest globally, indicators have been proposed for a wide range of different projects. The distinction between indicators is unclear. A project to clarify indicator issues was established by the European Union to link partners working with real data at a local level to highlight problems and discuss possibilities for rationalisation across systems. The major issues relate to indicator structure. They can have single or multiple components and be measured at different scales: local, community, regional, national and international. Many different frameworks exist and which may not be compatible. The quality of indicators across different systems, sectors and themes is reflected in the degree of difference in their definitions and calculation. Finally, the papers in this Special Issue are described. Appendix A gives a definition of an indicator. (C) 2001 Elsevier Science B.V. All rights reserved.