A. - Valuation toolsA number of valuation tools are available that, when applied carefully and according to best practice, can provide useful and reliable information on the changes in the value of non-marketed ecosystem services that result (or would result) from management decisions or from other human activities (see the appendix below). Data requirements may be quite demanding for a number of tools, as are the preconditions in terms of technical expertise. Moreover, conducting primary valuation studies is typically time-consuming and costly. Therefore, other approaches, including deliberative mechanisms that bring to bear non-economic considerations, will often be needed to support final decision-making.Efficiency. A cost/benefit criterion should be applied, as appropriate, to the valuation study itself. In principle, valuation techniques or tools should be used when the anticipated incremental (including long-term) improvements in the decision are commensurate with the costs of undertaking the valuation.Choice of valuation tools. The choice of the valuation tool or valuation tools in any given instance will be informed by the characteristics of the case, including the scale of the problem and the types of value deemed to be most relevant, and by data availability. Several techniques have been specifically developed to cater to the characteristics of particular problems, while others are very broadly applicable but may have other limitations that should be taken fully into account when choosing the appropriate tool or set of tools. Different approaches can be used in a complementary manner. In general, tools based on observed behaviour (the so-called revealed-preference techniques) are preferred to tools based on hypothetical behaviour (the so-called stated-preference techniques).Stated-preference techniques. Stated-preference techniques are, however the only techniques that are able to capture non-use (or passive‑use) values, which tend to be important in certain biodiversity contexts, and can provide useful and reliable information when used carefully and in accordance with authoritative best practice. Limitations of stated-preference techniques include: (i) the detail of information needed by respondents in order to value complex processes or unfamiliar species or ecosystem functions; (ii) difficult external validation of the results; and (iii) the need for extensive pre‑testing and survey work, implying that this technique can be expensive and time consuming. Their application could therefore be considered if all of the following conditions are met: (i) non-use values are expected to be an important component of the value of the ecosystem service under consideration; (ii) it can be ensured that the sample group of respondents is representative and has an adequate understanding of the issue in question; and (iii) capacity requirements for an application in accordance with best practice, including adequate skills in survey design, are met.Cost-based approaches. Cost-based approaches can provide useful guidance, if the nature and extent of physical damage expected is predictable and if the cost to replace or restore damaged assets, and the resulting ecosystem services, can be estimated with a reasonable degree of accuracy, and does not exceed the value of the ecosystem services in the first place. These approaches can in particular be used when the specific decision-making problem calls for a comparison of the costs resulting from different replacement or restoration options to meet a specific objective, and there is a general view that the benefits associated with meeting the objective outweigh the costs.Benefits transfer. Benefits transfer can provide valid and reliable estimates under certain conditions, including: (i) that the commodity or service being valued be very similar at the site where the estimates were made and the site where they are applied; (ii) that the populations affected have very similar characteristics; and (iii) that the original estimates being transferred must themselves be reliable. When used cautiously, it has the potential to alleviate the problems of deficient primary data sets and limited funds often encountered in valuation. However, benefits transfer is still a developing subject. More work needs to be undertaken to assess its validity in studies where it has been used to value biodiversity. Cautious application and further development of this method needs to be undertaken.