Background/Question/Methods Phenology is one of the most sensitive biological responses to climate change. Because of phenology's ubiquitous role in ecological relationships and processes, including plant-pollinator relationships and the water cycle among others, changes in phenology can have substantial consequences for plants and animals. Many recent studies of phenology have documented the advance of spring events, like flowering and bird migrations, and delays in fall events, like leaf coloring. These changes are often documented without considering the implications of the changes for conservation and management of species and ecosystems. Our understanding of phenological responses to climate change has advanced to a point, however, where some of the implications are becoming clear. In this talk, I will review how recent shifts in phenology will likely affect the abundance of species and what they might mean for on-the-ground management practices. Results/Conclusions The phenologies of some species are changing rapidly, while others are changing slowly or not at all. These changes are disrupting some timing-sensitive interactions, including plant-herbivore relationships and the timing of exposure to environmental stresses such as frost and drought. In several cases, changes in phenology have caused populations to decline or disappear. Intriguingly, new research suggests that the strength of a species' phenological response to variations in climate might indicate its vulnerability to climate change—populations with phenologies that track climate tend to perform well, whereas those that do not track climate tend to decline. The mechanism is still not clear. From the accumulated evidence, though, it is possible to formulate a conceptual model for using phenology in rapid assessments of species vulnerability, particularly in a changing climate. For example, managers and conservation biologists could target efforts to preserve species with phenologies that are not shifting in concert with climatic conditions. This includes most long-distance migratory birds and many plants species. Such a conceptual model could help conservation practitioners take concrete actions to protect the species most vulnerable to climate change.