The impacts on ecosystems depend on local, seasonal and temporal parameters, and may even vary during the course of a day (e.g., light or noise pollution). They also depend on how the different pressures interact within a region or season.
Accordingly, specifying the impacts that pressures have on ecosystems and biodiversity is more complex than, e.g., specifying the relationship between GHG emissions and global warming. However, given that many economic and political activities have consequences far beyond the local environment, it is nevertheless necessary to specify these impacts in a globally applicable and comparable way, if we are to include them in political and economic decision making. This will inevitably involve certain compromises and inaccuracies in the resulting metrics, which have to be weighed against the advantages of integrating ecosystem and biodiversity impacts into policy and investment decisions.
The Ecosystem Services Valuation Database (ESVD) provides the largest open access collection of scientific studies on the economic valuation of ecosystem services available to date and, in our view, is the best existing reference. If the economic valuation of an ecosystem service is required for a particular situation or decision that is covered by the ESVD studies, and the ecosystem service is only compared to similar services under similar circumstances (e.g., similar socio-economic conditions and ecosystems), the database provides valuable guidance. The available data is, however, not yet sufficient to derive generalized value factors for this handbook.
The same applies to the methods and data available for the economic valuation of biodiversity.
Further can be found in Chapter 9 of the Handbook on Environmental Value Factors – Methodological Convention 4.0 for the Assessment of Environmental Impacts.