Background/Question/Methods   Phenology is one of the most sensitive biological responses to climate change and is a critical aspect of nearly all ecological processes and relationships. Climate-driven changes in the timing of plant and animal life cycles and behaviors have been documented on every continent and in the oceans. These shifts in phenology have been linked to temporal mismatches, changes in community composition, the success of invasive species, and changes in carbon and water cycling. Despite their ubiquity and diverse impacts, phenological shifts have not yet been incorporated into most forecasts of ecological responses to climate change, particularly forecasts of changes in species ranges or abundance. In part, this is because we lack phenological data for many species and because we do not yet have an adequate framework for incorporating phenology into these forecasts.

Results/Conclusions   I will discuss the availability and utility of several sources of phenological data and how they can be used to describe past impacts and inform forecasts of changes in the abundance and distribution of species. Data sources include traditional long-term studies, unconventional sources such as herbarium specimens and photographs, and new sources such as data collected by the USA National Phenology Network. Data from these various sources have been used to show how phenological responses are, for example, related to shifts in the distributions of species up mountain slopes in Colorado and to declines in the abundance of native species and the spread of invasive species in Massachusetts. I will present these case studies and discuss how they could more broadly inform forecasts of ecological responses to climate change.