Plants have evolved to represent a diversity of species, characterized by functional traits that dictate their performance in response to changing environments. One such leaf functional trait that relates to plant ecological strategy and is strongly correlated with photosynthetic rates, is minor leaf vein density (LVD). Our study will assess how ecological strategies within plant communities shifted in response to Earth’s most recent major global warming event, the Middle Miocene Climatic Optimum (MMCO) from 17-14 Ma, where rises in both global temperature and atmospheric CO2 levels occurred. We hypothesize that global warming led to longer growing seasons and ecological strategies that prioritized persistence over productivity became dominant, and more favorable climates increased the diversity of ecological strategies present within the community. We will be traveling to various museums to photograph fossils that have all their minor veins preserved, collected from sites representing before, during, and after the MMCO in the Pacific Northwest region. Our goal will be to include several species per site, and photograph their fossil leaves under a stereo microscope. From there we will measure LVD using the program ImageJ using standard protocols. Once we have that data, we will calculate measures of the community-level distribution of this trait (mean, variance, kurtosis), and then compare those values between sites, and thus across the MMCO. In support of our hypothesis, we predict to see a lower mean and kurtosis, and higher variance of LVD values in MMCO plant communities, relative to those existing before or after the warming event. Overall this research is important to not only understanding how plant communities responded in ancient times to rising temperature but how plant communities could potentially respond to the rising temperatures in the future.