Environmental indicators are useful for several reasons, including:
Further refinements can be made to provide more useful information to policy makers. Response indicators can be developed to describe what society is doing to deal with environmental problems (such as environmental abatement expenditures) or for public opinion. Performance indicators (such as those currently being developed by the OECD) can be devised which relate to clearly defined norms (legislative or scientifically based). In the longer term, indicators of sustainability are needed, as called for in Agenda 21; essentially this means addressing the question of what level of socio-economic development is compatible with a sustainable use of natural resources, which in turn requires some notion of appropriate norms of sustainability.