No Park Is an Island: Increase in Interference from outside as Park Size Decreases

Abstract

As areas of conserved pristine forest are reduced in size they are increasingly susceptible to significant immigration of animals and plants from nearby anthropogenic secondary successional habitats, and the animals of the pristine forest are also likely to forage outside of the pristine forest in the food-rich secondary succession. This phenomenon should be of particular importance to the interactions that occur in natural disturbance sites within pristine forest (e.g., succession in tree falls). However, since much large tree regeneration begins in tree fall gaps in the canopy, even the composition of the canopy may be influenced by large bodies of non-pristine vegetation surrounding the preserved area. From a conservation standpoint, this emphasizes that in some cases a patch of pristine forest may remain ecologically intact longer if surrounded by croplands and closely grazed pastures than if surrounded by extensive areas of secondary succession rich in plants and animals that will invade the pristine forest. Colonization of a tree fall by Cecropia peltata trees in pristine forest in Santa Rosa National Park, northwestern Costa Rica is used as an example. The phenomenon emphasizes some of the ways that small islands of vegetation may be only poorly analogous to more conventional islands surrounded by water.