The importance of taking account of the total economic value of ecosystems is stressed and the possible reasons why the Millennium Ecosystem Assessment (2005) emphasised the importance of ecosystem services for biodiversity conservation is discussed. It is suggested that the Millennium Ecosystem Assessment does not give enough attention to the disservices association with some ecosystems nor to the comparisons of the value of alternative ecosystems. Reasons why it is important to estimate the total economic value of ecosystems are outlined. It is argued that the economic valuation of ecosystems is of little value unless it compares the economic value of alternative ecosystems or forms of land use. Most published economic valuations of ecosystems fail to do this or only do it to a very limited extent. The cost of replacing ecosystem services if an ecosystem is lost is sometimes used to value its services. In most cases (but not all cases), this tends to over value the loss. This is illustrated using some simple graphs. There is also the further complication that if one type of ecosystem is replaced by another form of land or aquatic use, some ecosystem services may continue to be supplied, possibly in reduced quantities or qualities. In such cases, assuming that the pre-existing services are totally lost and need to be replaced completely overstates the economic value lost, or in other words, the value of retaining an existing ecosystem.