Islands are cradles of biodiversity – home to many species found nowhere else on our planet. This project will document the biodiversity of islands located within the iconic yet understudied coastal lands and waters of the Gulf of Maine. Through surveys carried out by academic and community scientists alike, this research will explore the environmental and human factors that shape North America’s island mammal populations, spanning the ancient retreat of glaciers through present-day sea level rise, habitat change, and the arrival of invasive species. These unique ecosystems sustain the Gulf of Maine’s “blue economy”, contribute to globally relevant fisheries, and attract thousands of nature-based tourists annually. This project will generate multiple types of data that can guide conservation decision-making and will strengthen pathways for knowledge sharing between rural communities and wildlife managers. By building STEM identities at high schools and a primarily undergraduate institution, this project enhances our national STEM workforce and promotes scientific progress in a region where conserving biodiversity is closely tied to vibrant local livelihoods. This project advances NSF’s priorities in Biotechnology and Artificial Intelligence. Identifying the biogeographic factors that produce variation across scales— from genes and species to clades and ecosystems— is vital not only for understanding the past but is increasingly relevant to predicting future conservation challenges. Island systems serve as natural laboratories for studying the processes that govern the evolution and distribution of biodiversity on our planet, yet the long-term legacies of human activities are not traditionally integrated into biogeographic assessments. This project will systematically catalogue the diversity of mammals over the past ~12,000 years in three island meta-archipelagoes of the Gulf of Maine, using a combination of museum collections, historical archives, biological surv