Credible targets for environmental management : evaluating reconstructions of reference values for ecological status in surface waters
Sammanfattning: In the year 2000, countries of the European Union agreed to harmonise water management by implementing the European Water Framework Directive (WFD). The WFD uses good ecological status as the overall goal, which is defined as minor deviation from an undisturbed state. Reference conditions provide the means of estimating water status and ecological integrity, which are the focal point of decision-making processes. When determining reference conditions, the WFD prescribes the use of all available knowledge so as to reduce the predictive uncertainties. While the goal of achieving conditions similar to an undisturbed state can be desirable, the use of reference conditions as a target creates inherent complexity on multiple levels. This thesis focuses on evaluating the implications of different interpretations and implementations of WFD reference conditions for status assessment of Swedish surface waters. Specifically, the objectives were to: (I) define the implications of different reference condition criteria and understand the diversity of ways in which the term is used, (II) compare independent estimates of reference conditions estimated using historical fish archives and biogeochemical modelling for acidification assessment, (III) evaluate recovery from acidification of acid sensitive Swedish lakes and analyse potential confounding factors influencing future management, (IV) develop empirical models to estimate historical and present temporal trends in lake total organic carbon concentrations. Together and individually these studies have developed methods and models in which predictive uncertainties associated with reference conditions have been reduced. This thesis show how multiple methods can be used to reduce the uncertainties in surface water reference condition estimates as well as presenting approaches to the use of all available information as prescribed by the WFD. Furthermore, this thesis highlight the multiple competing, but equally valid, approaches to estimate reference conditions based on knowledge from different sources. In this thesis, it is argued that representations of the undisturbed state are a moving target and greater acceptance for multiple reference conditions based on all available knowledge is needed.
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