This dissertation examines the socio-economic and ecological outcomes of emerging payment for ecosystem services (PES) programs targeting highland Andean grasslands (páramos) in Ecuador. While PES programs, in general, and in Ecuador in particular, are increasingly advocated as a way to link conservation and rural development, there is a noted lack of empirical research on the social and ecological outcomes of these initiatives. The primary objective of this research was to contribute to filling this gap. Chapter 2 focuses on Ecuador's SocioPáramo program, a national-scale PES program targeting carbon, water, biodiversity, and poverty alleviation páramo grasslands. Participation resulted in gains in financial and non-financial capital, but outcomes depended on the context under which PES occurs. In many cases, PES strengthens adaptive capacity by providing a more diversified income source, but, in some cases, participation may increase vulnerability due to reduced access to permanent and seasonal grazing lands. Chapters 3 & 4 address changes in carbon storage and plant diversity under afforestation and burn exclusion, the two main land-use changes currently promoted by PES programs targeting páramos. Pine afforestation and burn exclusion increased aboveground carbon storage and had small, but variable, influence on soil carbon storage. Results suggest little immediate impact of fire on soil carbon storage, but that burn exclusion can lead to small increases in soil carbon storage, at least when some tussock cover is maintained. In both study areas, intermediate levels of burning maximized species richness, but results suggest that a mosaic of burn histories likely enhances landscape level plant diversity and richness. Pine afforestation led to a dramatic decrease in species richness in one field site, but supported a high diversity of species in another. However, in both sites, plant composition was dramatically different under pine than in native grasslands. These results constitute a significant step forward in better understanding PES in an applied context and are relevant for PES program development, particularly for programs targeting páramo grasslands. These findings can contribute to the development of more equitable and effective PES programs that help to protect the páramo for its ecological, cultural, and economic value.