Ideally, we would develop an entire dashboard of indicators—economy, health, environment—and accord them all equal or similar weight in policy decisions. In practice, however, economic decisions often dominate. That is why it is essential to create monetary measurements of the environment or health and education, and integrate them with existing GDP measures.

When it comes to balancing 50 jobs against 50,000 trees, logging companies are able to point to hard economic data while environmental activists must plead for the sympathy vote with pictures of virgin forests and perhaps a fuzzy baby animal. But it is indeed possible to calculate the economic worth of trees left standing. They are natural water and air filters. Providing clean drinking water and removing carbon dioxide from the atmosphere add real value to society. Another sizeable part of the equation is the recreational value of forests and their contribution to the tourism industry.

Green GDP is not the result of green accounting; it is simply good accounting. The more data that the policymakers have to steer a country’s economy, the better. It is technically feasible to create such monetary measurements of our environment. What remains to be done now is the actual counting.

Gernot Wagner, a consultant in New York, served as the 2007 Peter Martin Fellow on the editorial board of the Financial Times.