Not all that is very useful commands high value (water, for example) and not everything that has a high value is very useful (such as a diamond). This example expresses not one but two major learning challenges that society faces today. Firstly, we are still learning the “nature of value”, as we broaden our concept of “capital” to encompass human capital, social capital and natural capital. By recognizing and by seeking to grow or conserve these other “capitals” we are working our way towards sustainability. Secondly, we are still struggling to find the “value of nature”. Nature is the source of much value to us every day, and yet it mostly bypasses markets, escapes pricing and defies valuation. This lack of valuation is, we are discovering, an underlying cause for the observed degradation of ecosystems and the loss of biodiversity. Our project on “The Economics of Ecosystems and Biodiversity” is about addressing this second challenge, and making a comprehensive and compelling economic case for conservation of ecosystems and biodiversity.