Accounting for the assimilative capacity of water systems in Scotland

A key methodological challenge in understanding the relationship between the economy and the underlying ecosystem base resides in how to account for the ecosystem’s degradation and the decline of associated ecosystem services. In this study, we use information on nutrients and metals concentrations from the Environmental Change Network (ECN) database and the Scottish Environment Protection Agency (SEPA) for the period 2000–2010 in order to assess the assimilation capacity of water systems. The research covers five upstream sites and 17 downstream sites in northeast Scotland. Our results highlight the relevance of considering a number of pollutants, and suggest that elements such as arsenic, lead and mercury can pose a threat to ecosystems’ sustainability and health. However, little research has been done in terms of their assimilation capacity and their impact on grey water footprint assessments. In addition, the results indicate that background conditions might be relevant when performing sustainability analysis at different spatial scales. The study also poses relevant questions in relation to land management approaches versus traditional ‘end-of-pipe’ water treatment approaches, and the definition of maximum and background concentrations. In this regard, further studies will be required to understand the trade-offs between different ecosystem services depending on how these concentrations are defined.