This dissertation engages with the wicked problem of agriculture-driven nutrient pollution in transboundary basins. The Lielupe River Basin, shared between Latvia and Lithuania, provides a practical example of this issue. This thesis proposes ways forward to address this problem by crafting and using environmental models in participatory and systematic ways.

Modelling the environment with stakeholders adopts a systems perspective in connecting theory with practice. Theoretically, we investigate how participation, uncertainty and ethics can be included in model development for socio-environmental problems. Practically, we explore the added value of implementing participatory modelling in transboundary river management using the Lielupe basin as a case study.

Researchers and practitioners can find two theoretical contributions: (1) a flexible 3-phase modelling framework for addressing socio-environmental issues; (2) a structured set of ethical questions when engaging in participatory modelling.

Empirical contributions are specific to the Lielupe River Basin yet provide insights that are potentially transferable to other cases. Our results indicate that moderate cooperative land-use change scenarios outperform ambitious unilateral actions, helping to achieve basin-wide water quality objectives a decade faster – a critical finding for the Baltic region and the achievement of EU water quality objectives. We also show that model evolution and participants’ learning are socially driven across and beyond a modelling cycle.

This thesis contributes towards a more reflective and transparent modelling practice. It provides environmental modellers with practical tools for jointly developing and using models with stakeholders. The dissertation concludes with a call to modellers to consider how modelling can support broader participatory engagement processes rather than how participatory engagement can support modelling.

Managing natural resources in transboundary river basins is a complex task in which societal needs and environmental impact are intertwined. The nexus paradigm engages with such a challenge by analysing synergies and trade-offs across Water-Energy-Food-Ecosystems (WEFE) sectors. We present a WEFE nexus operationalisation using a participatory modelling approach in the transboundary Lielupe river basin, shared between Latvia and Lithuania. Using a modelling cycle approach, we illustrate a stakeholder-driven pathway from generic and qualitative to increasingly quantitative system tools useful for basin-scale policy analysis. Stakeholders prioritised agricultural nutrient pollution as a critical nexus issue strongly linked to land-use. Three policy alternatives to address this issue were co-identified with stakeholders from both riparian countries: (i) implementing nature-based solutions; (ii) transitioning to organic agriculture; and (iii) promoting arable land-use transitions to former native landscapes. The long-term effect of such policies is explored using a System Dynamics simulation model. Results highlight the importance of promoting active transboundary cooperation for water quality control, as unilateral action hampers the effect of long-term ambitious policies. Even highly ambitious unilateral action can delay the achievement of river basin quality objectives in the order of a decade, a critical finding for the wider Baltic region and the achievement of EU water quality objectives. Based on an exploratory analysis, we found that implementing basin-scale solutions for nutrient control would reduce nitrogen concentration by around 30 % with a 2 % co-benefit of increasing vegetation stocks, yet at the cost of decreasing cereal production by 8 %. This work illustrates the capabilities of a tailor-made simulation model crafted to answer locally relevant policy questions with a nexus perspective in a transboundary river basin. Developing and using a simulation model in a participatory way can explore policy futures while fostering dialogue among riparian stakeholders. This is a promising way to promote cooperation towards solving critical socio-environmental issues in transboundary rivers.

Integrated approaches for managing natural resources are said to meet increasing demand for water, energy, and food, while maintaining the integrity of ecosystems, and ensuring equitable access to resources. The Water-Energy-Food (WEF) Nexus has been proposed as a cross-sectoral approach to manage trade-offs and exploit synergies that arise among these sectors. Although not initially included as a component of the Nexus, the role of nature in sustaining the water, energy, and food sectors and in regulating their interrelationships is increasingly recognised by Nexus researchers and practitioners. To converge existing approaches that integrate nature into the WEF Nexus and suggest a common framework, we – an interdisciplinary group of natural resources management researchers and systems thinkers from the European research network NEXUSNET COST Action – followed a collaborative process of knowledge creation combining literature review, elicitation of expert opinion and collaborative writing. Our results reveal a multiplicity of concepts utilised in the literature to represent, partially or fully, “nature” in the Nexus, such as “environment”, “ecosystems”, “ecosystem services”, “social-ecological systems”, and “biodiversity”. Disparity was also found in the role attributed to nature, represented by three key paradigms: (1) ecosystems as the fourth component of an expanded Nexus, i.e., the WEF-Ecosystems (WEFE) Nexus; (2) ecosystems as a foundational layer to the Nexus; and (3) the WEF Nexus as a central component of social-ecological systems (SES). By creating a hybrid approach that brings together the benefits of the respective paradigms, we present a forward-looking WEFE Nexus conceptualisation. This paradigm expands the mutual interlinkages among water, energy and food to the entirety of SES, thus acknowledging the social-ecological processes that are affected by and affect the WEF Nexus. The results of this collaborative research effort intend to provide researchers and stakeholders with means to better understand and ultimately manage Nexus issues towards a transformative change.

The authors regret that there were two formatting mistakes: 1. Definitions of key “Nexus” and “ecosystems” terms appear as a paragraph on page 4 rather than within Box 1. The revised Box 1 is [Table presented] Box 1. Glossary of key terms. 2. The caption for Fig. 7 is separated from the figure and appears as a paragraph on page 15. The revised caption of Fig. 7 is[Figure presented] Fig. 7. Proposed hybrid WEFE Nexus paradigm – elements and interlinkages. Examples for some of the interlinkages are provided. Connection 4: the provisioning ecosystem service of wild foods, but also the expected trends due to planning and strategic conservation efforts that can lead to an increase in their availability and use (Sajeev et al., 2023). Connection 5: the provisioning ecosystem service of wood and biomass, as well as the influence of the energy sector on the use and management of land resources. Connection 6: provisioning of fresh water and water purification as ecosystem services, on one hand, and policy and governance measures for protection and preservation of aquatic habitats and biodiversity, prevention of overexploitation of freshwater, sustaining environmental flows from reservoirs, on the other. Connection 7: the social and governance processes involved in setting aside land and resources for new sectoral developments (e.g., a new reservoir), as well as constraints to such new developments arising from policy (e.g., the EU biodiversity strategy for 2030) and social dynamics; sectoral activities providing livelihoods; global and national agreements setting targets on emissions reductions, as well the socio-economic implications of decarbonization plans (Plazas-Niño et al., 2022), just transition plans (Wang and Lo, 2021), and the economic transformation towards net-zero economies, job creation in emerging sectors, innovation and investment, and social adjustments (Krishnan et al., 2022). Connection 8: the impact of infrastructure development in the water sector (e.g., a new reservoir) on freshwater ecosystems; the impact of agricultural expansion on terrestrial ecosystems; the influence of biotic and abiotic components of ecosystems on the WEF Nexus sectors: pests and diseases, invasive species, pollination, river flow regimes, including floods and low flows. The authors would like to apologise for any inconvenience caused.

Problems manifested within social-ecological systems (SES) exhibit dynamic complexity and hold implications for current and future human well-being and environmental sustainability. The complexity of these issues, the ever-present uncertainty inherent to SES, and the multi-stakeholder settings in which they are discussed call for participatory modelling to support decision-making on socio-environmental issues. Yet, this challenging endeavour requires a structured approach — a modelling cycle — to facilitate engagement with the implications of participation and uncertainty as focal points for Good Modelling Practice (GMP). Here we propose an integrated policy analysis framework for SES modelling using System Dynamics (SD). This framework stems from integrating two existing modelling cycles that individually consider participation and uncertainty in SD modelling. Three global modelling phases and a set of tools to address the participation and uncertainty features in SES modelling are distinguished. The framework contributes to mainstreaming GMP, offering a structured model-based approach to enhance the robustness and social acceptance of policies on critical socio-environmental issues.

Water enables health, education, and economic well-being opportunities for humanity. Access to basic water and sanitation services, freshwater variability, and water storage are some of the dimensions that may impact on human development worldwide. Yet few studies quantitatively explore the relationship between water and human development. This study uses a statistical approach to quantify the Water-Human Development relation in a global sample, both in terms of correlation and causality between variables. Correlation is established using a multiple linear regression approach, while causality is explored by implementing the multi-spatial convergent cross mapping technique. Our study finds strong interdependence between water-related variables and human development globally. Access to water services positively influences the Human Development Index (HDI), seasonal variability of freshwater resources restricts it, and large water storage is not significant. The analysis is robust between 2000 and 2017, and implies that a 1% increment in a country's HDI is associated with a 1.3%–3.2% increment in water and sanitation access. Causal analyses show strong coupling, suggesting positive feedback between access to water services and HDI that could be exploited. Reaching Sustainable Development Goal 6 requires closing the water and sanitation access gaps while addressing freshwater variability challenges. This will result in global human development benefits.

The social-ecological systems (SES) approach elicits a broad understanding of some of the most pressing socionatural challenges (e.g. resource scarcity, biodiversity loss, and climate change) and the responsibility that humans have in addressing them. System dynamics has proven a powerful paradigm for dealing with complex SES-related issues. Here we discuss some ethical considerations of using system dynamics (SD) to model SES, something that is often either overlooked or discussed as an isolated issue. Sustainable development and human rights are used as ethical standpoints across the modelling cycle, opening the discussion around guiding principles that need to be considered when modelling SES. Based on these, a set of guiding ethical questions are identified and classified across a participatory SD modelling cycle. This structured approach is a simple yet potentially useful tool for SD practitioners to examine the ethical implications of their modelling endeavours in the context of grand societal challenges.