Phytoplankton blooms are an increasing concern for lake and reservoir management due to their rising frequency, intensity, and negative impacts on water quality and ecosystem functioning. Influenced by global change factors like climate change and intensified land use, especially urbanization and agriculture, these blooms are expected to become more common worldwide. Despite extensive research on bloom dynamics, mechanisms, and toxicity (notably of cyanobacteria), there is no comprehensive synthesis of their effects on ecosystem services. To address this, we conducted a systematic review of 48 studies globally documenting the impacts of phytoplankton blooms on key ecosystem services: fisheries, drinking water supply, and recreation. In fisheries, blooms cause significant losses primarily through fish mortality and habitat degradation, with toxins also reducing fish activity. Drinking water services experience serious disruptions, sometimes requiring costly treatment upgrades, while consumer complaints about taste and odor are common. Recreational activities suffer from swimming bans, decreased site attractiveness, and health risks. Toxic cyanobacterial blooms were the most frequently reported and damaging, though non-toxic algal blooms also cause notable problems. While some studies mention potential benefits of non-toxic blooms, these are limited and highly context-dependent. Our review also underscores the value of including grey literature alongside peer-reviewed studies to capture a fuller range of bloom impacts. Finally, we compiled cost estimates from various contexts, providing a benchmark for assessing the economic burden of phytoplankton blooms. The diversity and severity of impacts call for proactive, adaptive management strategies to mitigate disruptions and safeguard ecosystem services in lakes and reservoirs facing growing bloom pressures.

Onternational Organizations formulate and disseminate principles of good governance for issues such as urban water governance. These principles are formulated in universal and general terms, for example, more transparency or participation, and are intended to enhance governance effectiveness. Yet, the relationship between such principles and governance effectiveness is not linear. Different combinations of principles affect governance effectiveness differently, depending on the context. It raises the general question of the influence of policy instruments interactions on policy outcomes. We investigate two types of non-linearities. The first, direct non-linearities, are instrument-specific and characterized by two thresholds: a minimum level required to ensure effectiveness, and a second level beyond which positive effects begin to decrease marginally. The second type, compositional non-linearities, refers to the idea that policy instruments are most effective when combined in specific ways (joint effect) or by being an enabling condition for others. We study the case of urban water governance in 35 megacities worldwide, based on empirical data from OECD reports and a fuzzy-set Qualitative Comparative Analysis. The present study assesses the impact of assesses how combinations of economic, participatory, and regulatory policy instruments affect urban water loss, as a policy outcome. We found that price and wealth are important enabling conditions within the policy design. Regulation and participation have important joint effects and follow the logic of direct non-linearities. Their absence or excessive presence can be detrimental, but they are critical for effectiveness when combined with other policy instruments.

Environmental transitions face the challenge of incentivizing change and governing complexity. Changing perceptions is critical to address these challenges. Perceptions shape policy and directly determine the potential and pathway of environmental transitions. While often addressing risk perception, economists rarely study perceptions in regard of policy process and change. Social-Ecological System components interdependencies drive dynamics and potential for sustainability. We elicit the perceptions of these interdependencies, offering a comprehensive understanding of the mechanisms at stake by measuring three dimensions of perceptions: likelihood, intensity and polarization. Then, we investigate the mechanisms determining the perceptions, and the association of interdependencies perception with policy preferences. Empirically, human activities related to water serve as a case for investigation. We develop an original measurement of perception using a survey that puts the emphasis on the perceived interdependencies between water activities, while most of the literature measures the importance attributed to each activities. We focus on the 19 principal water-related human activities in the Geneva region, i.e., a system of 342 relations. Results show important variations in perception. This variation depends on individuals characteristics, and nature of water-related activities. Higher perceptions environmental externalities associate with preferences for broader participation and more stringent policy instruments, like precautionary principle.

Policy preferences are a key element in understanding the policy process. In this article, we conceptualise policy preferences as latent constructs, which can be identified in an inductive way, based on actors’ choice of policy instruments and organisational structures. To inductively identify policy preferences, we take an approach based on principal component analysis, informed by theory on preference formation. Using water supply in Switzerland as a case study, we propose an approach based on policy preference spaces to identify preferences based on clusters of choices. Our results show the presence of three distinct policy preferences: 1) local management with regional support, 2) local autonomy, and 3) strong regional management with local financing autonomy. We investigate the factors affecting the formation of these policy preferences through a regression analysis. Our results indicate that preference formation is affected by actor types and, to a lesser degree, by goal priority. In this way, the article makes two distinct contributions to the field. The first is a methodological contribution, through its proposition for measuring and operationalising policy preferences; and the second is a theoretical contribution, in demonstrating how policy preferences are influenced by actor types and goal priority it highlights the context-dependent nature of policy preferences.