Costa Rica’s environmental services payments program (Pagos por Servicios Ambientales, or PSA) started in 1997 and was the true pioneer in this area. It is broadly cited and has led to numerous calls for emulating its approach in various ways. It has itself evolved over time, with acknowledged...

Prioritizing sites for conservation has been a central question for over a century. Much work studies large sparsely-populated landscapes to optimize habitat for the highest number (or value) of species for a set cost, given possible ecological interactions between the patches of conserved land....