Nature in Denmark continues to lack space, and nitrogen leaching from agricultural lands remains a major pressure on aquatic ecosystems. Since the first Danish Action Plan on the Aquatic Environment in 1987, suc-cessive policies have relied on setting land aside through voluntary agri-environmental schemes to reduce ni-trogen losses and improve environmental conditions. This approach continues under the Danish Green Tri-partite Agreement (2024), which assumes that land set aside will contribute simultaneously to improved water quality and biodiversity (Økonomiministeriet, 2024). However, after four decades of implementation, many water bodies remain in poor ecological condition and biodiversity gains have been limited.

This raises a fundamental question: why does land-use change not consistently translate into ecological im-provements? The answer is likely to involve both biophysical conditions and the ways policies are imple-mented, interpreted and translated into management practices on the ground. Policy implementation affects outcomes (Winter & Nielsen, 2013). To understand how governance produces ecological results, we must understand how policy implementation shapes ecological outcomes in practice. Therefore, this PhD-project focuses on implementation, landowner motivation and how these factors influence the management of former agricultural land. The project is structured around three analytical components, which will be examined using mixed methods combining quantitative geodata with qualitative interviews. The three analytical components are:

1. Landowner motivation and participation:

1.1. What motivates landowners to engage in land set-aside schemes, and how do policy incentives influ-ence these decisions?

2. Governance and implementation processes

2.1. How does the regulatory framework and advisory system under the Green Tripartite Agreement shape decisions about where and how land is set aside?

3. Post-restoration management decisions

3.1. What factors and intensions influence management decisions on land set aside after restoration.

By assessing landowner motivation for setting land aside, the influence of the regulatory framework and advi-sory system and the intensions behind post-restoration management decisions, the project will hopefully pro-vide knowledge about how land-use change can better contribute to improved aquatic ecosystems and biodi-versity. The overarching aim is to learn how the implementation of agricultural policies, the surrounding ad-visory system and landowner motivation influence the ecological outcomes of setting agricultural land aside.