At the recent Green Building Conference organised by alive2green and held in Johannesburg over 13 and 14 July, Eamonn O’Rourke from Strategic Environmental Focus (SEF) offered delegates one of the most thought-provoking presentations. The title of O’Rourke’s presentation – Ecosystems have no value – certainly raised questions ahead of his taking the podium. However, he soon clarified that statement to say, actually, “Ecosystems have no Rand value. They are priceless.” How do we determine what is valuable? In his presentation O’Rourke explored the whole question of values, whether different value systems can be compared, and what value systems are appropriate when we consider plans for land use, built developments, site selection and construction. If something is priceless – is it of no value? How do we determine what is valuable and what is valueless?