Research Institute for
Sustainability | at GFZ

Why a source-to-sea approach is vital for a sustainable future of European seas

26.03.2026

Linda Del Savio

linda [dot] del [dot] savio [at] rifs-potsdam [dot] de

Ben Boteler

ben [dot] boteler [at] rifs-potsdam [dot] de
Water connects us all. Yet too often, our approaches to its governance remain divided. The EU wants to change that.
© istock/andrej67
Water connects us all. Yet too often, our approaches to its governance remain divided. The EU wants to change that.

The EU’s environmental governance is characterised by a sectoral approach, with policy domains such as freshwater management and marine conservation formulated and implemented in isolation. The need for a more integrated approach has been recognised by the EU and expressed in policy initiatives, such as the European Green Deal. Yet, a complex array of policies, management bodies, and actors forms the basis of EU governance, which operates with limited integration and fails to account for the interconnectedness of terrestrial and marine environments.

Marine ecosystems do not recognise jurisdictional and management boundaries and pollutants, such as microplastics, do not stop at the coastline. The health of European seas is inextricably linked to the lands and waters that feed into them. For example, land-based pollution, including agricultural runoff, industrial discharge and plastic pollution, impact marine health, often traveling vast distances through interconnected pathways. Thus, a holistic “source-to-sea” approach that recognises the interconnectedness of terrestrial and marine environments is gaining momentum as a much-needed approach to tackle interconnected policy challenges. It is central to ambitious initiatives like the European Ocean Pact.

What is the source-to-sea approach?

The source-to-sea approach recognises that aquatic systems function as an integrated system along a land-sea continuum. It advocates for managing the entire water cycle on land and at sea – from its pathways through agricultural lands and urban areas, river and sea basins and ultimately to the ocean – as an interconnected unit. It is not just about protecting the marine environment in the ocean, but about understanding and addressing the pressures on marine ecosystems throughout the entire land-sea continuum. The source-to-sea approach goes further than previous ideas for integrated water management, which often focus on the river as the central element, as it explicitly considers the transboundary nature of these systems. Most aquatic systems cross multiple administrative boundaries – including local, national, regional, and international. And, crucially, they ultimately connect to the ocean.

The European Ocean Pact and the need for policy integration

The European Ocean Pact, adopted in 2025, is an example of the EU’s commitment to a sustainable blue economy and healthy ocean. It proposes a framework for coordinated and targeted action, as well as for effective implementation, bringing together ocean-relevant policy goals and actions.

The Pact reinforces existing goals, such as achieving Good Environmental Status of marine waters, as outlined in the Marine Strategy Framework Directive (EC 2008/56), ensuring the conservation of marine biological resources and management of fisheries, as outlined in the Common Fisheries Policy Regulation (EU) 1380/2013, and banning certain single-use plastic items, as outlined in the Single-Use-Plastics Directive (EU 2019/904). As such, a key tenet of the Ocean Pact is the need for integrated policy.

Recognising that ocean health is not solely a marine issue, the European Ocean Pact explicitly promotes the source-to-sea approach as a vital component of tackling pollution and is one of four key principles that guide the proposed actions of the Ocean Pact. The others are the precautionary principle; a science-based approach to policy decisions; and an ecosystems-based approach to management. Source-to-sea specifically acknowledges that land-based sources of marine pollution, such as agricultural runoff, industrial discharge, and (micro)plastics, are major threats to marine ecosystems. Addressing these pollutants requires action upstream and at the source, not only in the sea and river basins that feed our ocean but also on land, where most human activities occur.

This requires collaborative, cross-sectoral action, bringing together governments, businesses, industries, non-governmental organisations (NGOs), and citizens from ‘source-to-sea’ to address the many challenges that span terrestrial, freshwater and marine environments. For example, the governance of tyre wear particles, a form of unintentionally released microplastics, includes the European Commission Directorate-Generals for Environment (DG ENV), for Internal Market, Industry, Entrepreneurship and SMEs (DG GROW), and for Mobility and Transport (DG MOVE), the car and tyre industry, environmental NGOs and civil society organizations protecting consumers’ interests, the wastewater treatment sector, as well as academia and technical experts, among others.

Why is the source-to-sea approach important?

Integrating a source-to-sea approach into policy considerations provides numerous benefits for governance and management. As governance bodies often operate in silos, with different agencies responsible for freshwater and marine environments, identifying such disconnects in roles and responsibilities is the first step towards coordinated policy-making. Further, finding policy approaches that balance economic development with environmental protection requires effective stakeholder processes which integrates both upstream and downstream considerations into decision making. Data gaps on water quality, biodiversity, and land use can hinder effective management. Viewing data through a source-to-sea approach can help to recognise critical connections within pollutant pathways, and in turn help to determine where to invest and cooperate in monitoring and data collection.

Finally, managing the land-sea continuum requires international cooperation. For instance, pollution can originate from non-point sources across vast landscapes, making it difficult to trace it back to its original source. Furthermore, multiple ecosystems, including shared river and sea basins and shared marine resources, like fish stocks, marine mammals and coral reefs are affected, requiring transboundary cooperation. This can be complex and time-consuming due to the number of upstream and downstream actors involved.

Our recent research, as part of the Horizon Europe project ‘Source to Seas – Zero Pollution 2030’, highlights how a disconnect between upstream and downstream actors and a lack of coordination across EU policies hamper approaches to address plastic pollution. A key finding is that conflicting priorities between different policy areas contribute to the plastic pollution problem. For example, the promotion of electric vehicles, which are heavier than traditional cars and require different tyre designs, can inadvertently contribute to increased microplastic pollution from tyre wear – a significant and often overlooked source.

Applying a source-to-sea approach to plastic pollution policy integration can bridge the gap between traditionally distinct policy areas (e.g., mobility, climate and environment). As such, the approach provides a tool to map the policies and actors along the pollutant pathway (e.g., land and water) and across the pollutant’s lifecycle stages (e.g., production, use, end-of-life stage). In doing so, the approach highlights where policy alignment is needed to effectively integrate policies relevant to addressing marine plastic pollution.

Moving forward

The European Ocean Pact proposes a new strategy for policy integration and EU ocean governance by embracing the source-to-sea approach. This initiative seeks to integrate policy, foster collaboration across sectors and jurisdictional borders, and drive targeted research—all aimed at embedding the land-sea continuum into EU policy frameworks. There is currently work underway by the EU Member States on the Ocean Pact, including a future Ocean Act, which is a legislative proposal aimed at revising the Maritime Spatial Planning Directive (EU 2014/89) and bringing all existing EU ocean-related targets together in a single legislative act. Moving forward, the future Ocean Act could require that objectives for marine environmental protection consider upstream drivers and that River Basin Management Plans demonstrate alignment with marine environmental targets (land-sea coordination). Furthermore, the Ocean Act could strengthen the science-policy interface by establishing a source-to-sea advisory platform with representatives of the land-sea continuum guiding the work to attain the above objectives and support governance alignment.

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Keywords

Oceans