There are now a large number of valuation studies on the benefits of biodiversity and on ecosystem services, the services provided by different ecosystems (ESS). Both ideas have been used to elicit values from nature but in recent years the research community has focussed on ESS as the main organising framework, with some additional use of the biodiversity concept to value entities that have intrinsic value and are of an extraordinary nature. Estimates are available for the services from most habitats, by type of ecosystem service, usually expressed in USD per hectare per year. Coverage varies by habitat and region, as does the quality of the assessment, but it is possible now to carry out an estimation of changes in values for a number of ecosystem services a result of the introduction of a new policy or of a physical investment that modifies the ecosystem. While this is a positive development, there remain some issues to be resolved. One is the possibility of double-counting of services when using the standard categories of provisioning, regulating/supporting and cultural ESS. Regulating and supporting services are the basis of the provisioning services and so value estimates for the two cannot always be added up. For example, air pollution absorption is often valued using the cost of alternative ways of reducing the pollutants from the atmosphere while recreation is often valued in terms of willingness-to-pay (WTP) through stated preference methods. The literature reveals wide spatial variability in values for services by habitat. This factor has been underscored in the recent research that values ESS on a spatial basis, such as the global assessments conducted as part of The Economics of Ecosystems and Biodiversity (TEEB) and the national ecosystem assessments (NEA) in the UK. At the local level, there are relatively few studies that actually conduct a full blown cost-benefit analysis relative to the number of studies that estimate the value of ESS. One reason is the need to estimate changes in ESS as a function of a policy change, rather than value the ESS in their current form, and difficulties in linking policy changes to changes in ESS. A number of other key points emerge from the review. One relates to the role of benefit transfer compared to primary data collection. For policy assessment and cost-benefit analysis, primary data collection seems to be required quite often. This may reflect the literature surveyed, which was from leading journals in the field, but it also reflects the fact that changes in ESS are not so easily valued on the basis of the existing literature. Other points noted relate to the methods of elicitation, the range of ESS coverage, the importance of sensitivity analysis and of evaluating the distribution of costs and benefits as well as of their total value. On methods, there is still some scepticism on the use of stated preferences or indirect valuation methods compared to methods that rely on market information. However, the evidence shows that non-market methods can give reliable estimates of values, and for some categories of value, such as non-use, they are the only method available. Given the uncertainty about many of the key parameters, sensitivity analysis has to be part of the toolkit of cost-benefit analysis when ESS are involved. Lastly, in many situations where the appraisal involves comparing gains or losses from ESS against other costs and benefits, there are important distributional considerations. These have to be taken into account in making decisions where the trade-offs between conservation of natural capital or development are at the heart of the debate. The acceptability and use of cost-benefit methods with ESS for policy purposes is still relatively limited. Commentators have noted the increasing sensitisation of policy makers to economic values of ESS, which is encouraging, but examples where policies have been influenced by a formal analysis of benefits and costs are still few. One can expect an increased use of these methods as governments become more convinced of their credibility and begin to see how they can help in making decisions of greater benefit to society. [ABSTRACT FROM AUTHOR]