This sub-section documents the methods and concepts that are useful to assess the potential impacts of ecosystem services and their change on human well-being. The Millennium Ecosystem Assessment analyses are based on a multidimensional definition of human well-being, which includes, but is not restricted to monetary income. Several initiatives have proposed indicators and composite indices of human well-being.
Assessing the links between ecosystem services (Ecosystems and ecosystem services) and human well-being first relies on the causal pathway between ecosystem services and human well-being, including the identification of those human populations that are most vulnerable to a change in ecosystem services. This analysis can identify trade-offs between ecosystem services: enhancing one service (for example food or timber production) usually affects other services to human society, sometimes at very different scales (for example climate regulation). These trade-offs can be positive or negative.
Quantification of these links is useful for analysing policy options (Response options). For this purpose, tools are being developed to ascribe monetary values to ecosystem services, even when they are not marketed. The Millennium Ecosystem Assessment has suggested a framework for the total economic value, distinguishing ‘use’ and ‘non-use’ values. The relevant approach is marginal analysis where the value of changes in the flow of ecosystem services is assessed and balanced against the costs of mitigating and adaptive measures. The concept of marginal analysis implies scenario analysis (Scenarios), describing possible future states of the environment, and focusing on changes in the flow of ecosystem services that would be associated with these alternative developments.