Managing the environment implies to allocate limited resources in light of unlimited, contrary and unknown demands. The complexity of this undertaking is evidenced by anthropogenic activities leading to ecosystem degradations and collapses worldwide. One of many examples are the water bodies in the Baltic Sea Region, which provide livelihoods and recreational values for millions of people yet have to deal with severe anthropogenic pressures. For instance, nutrient inputs through agriculture and wastewater causes eutrophication, which adversely affects a range of ecosystem services that generate societal welfare. In the face of climate change, population growth and intensive agricultural production, more efforts are required to harness the services provided by nature in a way that benefits current and future generations in a sustainable manner. Yet, any intervention is shaped by complex social and ecological interactions, trade-offs, and often conflicting interests across local actors and society as a whole. Those that benefit from improvements frequently do not bear the costs. To implement solutions which are in line with the preferences of local stakeholders and the wider public, decisions must be made on a sound and holistic informational basis. This thesis presents four papers, which explore how such a basis can be provided. By combining economic reasoning and stakeholder engagement, the first three papers (Paper I-III) apply different variations of decision-support tools and suggest approaches which aim to provide arobust, yet practical, basis for optimal environmental planning and decision-making. The stakeholderdriven development processes of the approaches do thereby not only benefit from utilising local insights, but also support participatory processes. This includes providing the means of building understanding, fostering dialogue, increasing acceptance and enhancing social learning. Paper I assesses the cost-effectiveness of nutrient mitigation measures which were suggested by local stakeholders in three European river catchments. This paper demonstrated substantial variations incost-effectiveness across and within catchments, and the results underline the need for conducting local analyses to find the most cost-effective solutions. To capture the plurality of impacts, Paper II component is limited to qualitative assessments, the results demonstrate that stakeholder priorities and differing perspectives determine the selection of the most cost-effective approaches. The study therefore concludes by arguing that customising decision-support to the preferences of directly affected or responsible stakeholders may provide the information which is most relevant for selecting cost-effective solution approaches in the given context. As Paper I and II assess the cost-effectiveness and thus the relative performance of measures, the papers provide guidance on which of alternative measures to select to achieve a target at the lowest cost for society. In contrast, Paper III proposes a bottom-up approach to Cost-Benefit Analysis (CBA) which assesses the social costs and benefits of implementing management strategies as identified by local and directly affected stakeholders. The analysis therefore provides indications if any of the proposed strategies, from a society’s point of view, are worth undertaking or not. The final paper, Paper IV, does not apply a decision-support tool per se but further investigates the method of transferring monetary value estimates from a primary study site to another context. Decision-tools such as CBA frequently rely on so-called Benefit Transfer (BT), for instance when generating new benefit estimates is beyond the temporal or financial scope of the analysis. While it is commonly assumed that BT performance improves with increasing similarity of sites and goods, no common criteria for defining similarity exist. By drawing on value estimates for water quality improvements, Paper IV proposes a framework for distinguishing between similarity and dissimilarity in a structured manner. By disentangling various aspects in three dimensions ofsimilarity, the results of Paper IV demonstrate that similarity in terms of commodity and attribute descriptions play an important role to improve the performance of BT, whereas income adjustments surprisingly lead to reduced performance.Overall, the thesis explores the application a nd foundation of economic approaches to enhance environmental decision-making, and thereby emphasises the advantages and limitations of involving stakeholders into their development. The thesis contributes to bridging the gap between political and public demands, the sentiments of st akeholders, and local situations and environmental condition