The researchers studied how different features of protected areas affect the number of species living there. They looked at over 400 protected areas in the Americas and found that the size of the area positively influenced species richness, while the shape and fragmentation of the area had negative effects. The distance to the nearest protected area also played a role, with closer proximity benefiting mammals but not other animals. The researchers discovered that these spatial features interact with each other and with environmental factors, affecting species richness in complex ways. This study helps us understand how to design and manage protected areas to better support biodiversity.