The temporal character of global environmental problems creates a challenge for democratic multilevel governance. Long-term environmental goals frequently necessitate short-term political action. Short-term economic and societal costs, on the other hand, often can only be linked to long-term and partly uncertain effects. This becomes particularly pertinent when processes of change take place in multilevel settings. In such processes, claims of expert knowledge are essential to prioritize between often competing policy goals. At times, the validity of such knowledge-claims is simply taken for granted, whereas in other cases, expert knowledge tends to become highly politicized. In one way or another, expert knowledge is infused with power and as such particularly prone to turn into an object of political conflict. In this context, the apparent ability of the European Union to pursue ambitious policies oriented at long-term goals in some areas of environmental governance is puzzling. At the same time, the EU has failed to make similar strides in other areas of environmental governance. This paper enquires the differences in the EU’s ability to induce policy change in environmental governance in two cases: the EU’s fisheries and climate change governance.