Knowledge uncertainties are an important challenge for nature conservation governance. Although the legitimacy of science-based decisions is questioned by knowledge uncertainties, the dominance of scientific expertise in nature conservation has not reduced. This PhD thesis explains this paradox through an analysis of knowledge uncertainties in decision-making processes around a planned powerboat race, mussel fishery and seagrass restoration in the Dutch Wadden Sea. An analytical distinction is made between three types of knowledge uncertainties: incomplete knowledge, unpredictability and ambiguity. A key factor that explains why knowledge uncertainties have not reduced the dominance of science-based expertise in nature conservation governance is the dominant perception of uncertainty as incomplete knowledge among scientists as well as decision-makers. In order to adequately respond to knowledge debates, ambiguity triggered by diverging knowledge claims as well as the politics of knowledge uncertainties should be given due consideration.