In my dissertation research, I investigated how coastal fog influences the water relations and distribution of Bishop pine (Pinus muricata D. Don), a drought sensitive species restricted to the fog belt of coastal California and offshore islands. I will discuss three related projects motivated by the following research questions: 1) Can the current spatial pattern of Bishop pine mortality on Santa Cruz Island be explained by important environmental and biological controls on plant available water? 2) How do summertime fog water inputs affect the water status of Bishop pines? Do adult and sapling trees respond to fog differently? and 3) What is the relative importance of fog-drip and fog immersion to the physiological function of Bishop pine saplings? I addressed these questions by using a variety of approaches ranging from remote sensing techniques to field-based plant physiology. The outcomes of these studies provide evidence that coastal fog is an essential element to augmenting plant available water during the dry season and that its occurrence supports the southern extent of its range on Santa Cruz Island. Moreover, this work advances our ability to make mechanistically-based predictions of how foggy coastal forests may respond to a warmer, drier climate.