Measuring sustainability

A system of indicators

As just mentioned, the adjusted net savings indicator is a potentially useful headline indicator at the aggregate level. But unlike GDP-which is affected by economywide prices, such as exchange rates and interest rates, and which can be influenced by economywide policies-there are no policy-relevant aggregate indexes on the state of the environment. For policy purposes, these indexes need to be disaggregated (as in table 2.1) and complemented by such biophysical measures as pressure-response indicators. Not only can the latter be disaggregated to a much greater extent, but they also have the added advantage that they can be used to identify the source of the problem.

While recognizing the need for an aggregate index as a headline indicator, it is important to note that indicators are most useful when they address specific problems. To catalyze change, information and signals have to be picked up by specific groups or institutions that can use them to diagnose specific problems, rally support for change, balance interests, and take action. ⁹

A good example of this process is Silent Spring, the book Rachel Carson wrote in 1962 to alert the public that birds were disappearing or being silenced. She pointed to indicators that no government agency would have considered important in advance-DDT levels in falcons and the fragility of their eggs. This gave birdwatchers in America a new role and put environmental protection agencies on a track to monitor toxins in nature, industry, and elsewhere that might affect human well-being as well.

Policy-relevant indicators emerge and are continually validated and refined in an environment where there is a free flow of information and interaction. To avoid major regrets, there is a need for more credible information and networks that link experts, civil society, and decisionmakers.