While some of the future impacts of global environmental change such as some aspects of climate change can be projected and prepared for in advance, other effects are likely to surface as surprises - that is situations in which the behaviour in a system, or across systems, differs qualitatively from expectations. Here we analyse a set of institutional and political leadership challenges posed by 'cascading' ecological crises: abrupt ecological changes that propagate into societal crises that move through systems and spatial scales. We illustrate their underlying social and ecological drivers, and a range of institutional and political leadership challenges, which have been insufficiently elaborated by either crisis management researchers or institutional scholars. We conclude that even though these sorts of crises have parallels to other contingencies, there are a number of major differences resulting from the combination of a lack of early warnings, abrupt ecological change, and the mismatch between decision-making capabilities and the cross-scale dynamics of social-ecological change.