Privately owned lands adjacent or close to publically protected lands of great ecological value are widely recognized as playing a crucial role in either protecting or degrading those lands. This buffer role is especially important for the Reserva Forestal Golfo Dulce (RFGD) on Costa Rica’s Osa Peninsula, which connects two national parks, one of which (Corcovado) is often referred to as the “crown jewel” of the country’s park system. We have obtained the results of a recent land use survey of parcel owners along with related geocoded data for all parcels in the northern half of the RFGD and many in the southern half. The paper explores the factors that drive the spatial pattern of deforestation in the forest reserve buffering the two parks and examines how institutional complexity influences deforestation there. It concludes that overlapping institutional jurisdiction in two sub-regions of the reserve does affect their rate of deforestation.