The effects of protected area systems on ecosystem restoration: a quasi-experimental design to estimate the impact of Costa Rica's protected area system on forest regrowth

Global efforts to protect forest biodiversity and ecosystem services rely heavily on protected areas. Although these areas primarily aim to prevent losses from deforestation and degradation, they can also contribute to restoration. Previous evaluations of protected area impacts focus on avoided deforestation and fires. In contrast, we focus on the additional regrowth induced by Costa Rica's renowned system of parks and reserves. We use a quasi-experimental empirical design to control for confounding baseline characteristics that affect both regrowth and the assignment of protection. Between 1960 and 1997, an estimated 13.5% of previously unforested lands inside protected areas reforested because they were afforded protection. The level of additional regrowth does not vary by the strictness of protection. As in previous studies of protected area impacts on avoided deforestation, estimators that do not account for nonrandom assignment of protection can overstate protected areas' impacts on regrowth by nearly double.