This paper explores how contestation unfolds within the interconnected processes of governing, managing, and measuring nature, using Swedish forest policy and Woodland Key Habitats (WKHs) as a case study. It illustrates how contestation rooted in different interests and worldviews manifests as epistemic struggles within the state apparatus. Based on document analysis and expert interviews with policymakers, researchers, and stakeholders, the paper traces the development of WKHs since the 1990s as a method, grounded in an ecosystem approach, for measuring the ecological value of a forest, as well as the subsequent politicization and contestation of the method that has played out over the past decade. Rather than targeting political goals, the contestation is directed at the objectivity, legality, and reasonableness of WKHs. The contestation led to a revision of the classification criteria and eventually the termination of the assessments. This case underscores how the deep entanglement of values and facts is essential both for driving change and for understanding the limited implementation of more progressive ecosystem-oriented policies. Assessing this triadic interrelationship between governing, managing, and measuring nature provides a deeper understanding of how contestation plays out and impacts environmental governance.