The majority of Arctic wildlife populations migrate and reproduce on schedules that have evolved to optimally exploit habitat resources whose temporal availability and quality are directly influenced by climate conditions. Disruption to this synchrony through accelerated global change could introduce an unstable period of unknown length, as new equilibriums become established. Although the importance of climate in Arctic ecosystems has been recognized by wildlife scientists, little quantitative research has been conducted on establishing functional linkages between climate, habitat, and wildlife population dynamics. Understanding these linkages will be necessary to make scientifically-based inferences regarding the implications of global change to the biological resources of the Arctic. The Arctic National Wildlife Refuge (ANWR) coastal plain and the north Yukon of Canada are used annually as calving and post-calving habitat by the international Porcupine Caribou (Rangifer tarandus) Herd. Global warming will likely influence the timing of spring snow-melt and vegetation green-up, and hence, the availability and quality of forage resources during the calving period. Because the study area is very large and because the dynamics of snow melt and vegetation growth in the Arctic are temporally compressed, this study is designed to evaluate and employ Advanced Very High Resolution Radiometer AVHRR satellite imagery (which are acquired daily throughout the world) as a tool to investigate long-term annual variations and trends in the condition and quality of caribou calving habitats.