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Saltmarsh offers a wide range of different functions and services that are of value to people and, therefore, have a worth. This can be measured in a number of different ways. The easiest of which to understand is the concept of values having an economic worth that can be expressed in monetary terms. However, values can also be expressed in non-monetary terms, although such values are often more difficult to define.

According to Stuip et al., (2002) a number of different values can be defined according to the way that humans interact and benefit from the saltmarsh. That is:

• Use values are realised through human interaction -

• Direct use values relate to the products and benefits that can be derived from the use of a saltmarsh, such as food, materials and recreational use;
• Indirect use values arise from the benefits provided to existing activities or resources through their occurrence and can be thought of as services, for example, flood control; and
• Potential future use value arises where there is uncertainty over the future demand for a product or service and/or its availability in a saltmarsh in the future. The potential future use value reflects the need to estimate, for example, the benefit of conservation of the saltmarsh.

• Non-use values relate to the essential nature of a wetland and the worth that is placed on it by particular groups - examples of non-use values include biodiversity or heritage.

The table below summarises the main types of saltmarsh value and the categories that they fall into. Notionally, consideration of all of the value types will give an indication of the Total Economic Value of a saltmarsh.

Total economic value for wetlands

The concept of economic worth and definition of the functions of the feature (in this case saltmarsh) form the basis of economic appraisal. However, not all of the functions proposed for use in economic appraisal can be directly measured in monetary terms. Therefore, it may be necessary to identify ways in which impacts can be expressed as money values or to consider descriptive methods of valuation. There are a range of economic techniques available for placing a money value on impacts where a direct (e.g. market-value based) value is not available. (see approach to appraisal for further details).

More generically, project appraisal can be used at a variety of different levels for the assessment of management options, from identifying where impacts may occur through to their full monetary valuation. The aim of any project appraisal is to provide a decision-maker with clear information on the choices that have to be made. This does not necessarily make the choices any easier, however.

The amount of detail required for a project appraisal will depend upon the type of decision that has to be made. In many cases, it will be sufficient to describe potential (or realised) impacts to saltmarsh habitat, for example, in qualitative terms or to report impacts and proposed mitigation measures in their natural unit of measurement (e.g. number of hectares of a particular habitat type created or restored). In other cases, particularly where it is necessary to justify expenditure or to obtain funding, it may be necessary to report benefits in monetary terms (see valuing the impacts for further details). For example, the inclusion of managed realignment as part of a flood defence strategy will require full project appraisal, where appropriate, including monetary valuation.

The potential use of project appraisal techniques in assessing the economic as well as other potential values of saltmarsh can be assessed using Appraisal Summary Tables (ASTs).