Ecologists continue to debate the relative importance of biotic interactions such as predation, competition, and herbivory versus abiotic factors such as climate in regulating population and community dynamics. This project, now in its twentieth year, started as a large‐scale investigation of the importance of biotic interactions in a Chilean semiarid thorn scrub community. Excluding predators has had significant though transient effects on plants, herbivores and their predators, while high rainfall events have resulted in dramatic responses by all community members. Three of 5 El Niño (high rainfall) events during the last 10 years portend more frequent and intense El Niños, a predicted consequence of global climate change. These in turn may significantly alter the dynamics of important community components. Current objectives of the project are to assess the impact of changes in precipitation patterns on native vs. introduced species (especially rabbits and hares), in light of recent changes in the precipitation regime. New experiments will exclude rabbits or hares , and both rabbits or hares and small mammals, allowing the investigators to quantify the impacts of these herbivores while testing predictions for how global climate change-related alterations in precipitation will affect native plants, primary consumers, their predators, and interactions among these components.
The increasing evidence for effects of stronger and more frequent El Niño events in this Chilean community will provide a baseline for comparison with ongoing changes in arid‐semiarid systems worldwide. The project depends on a strong, intellectual collaboration with Chilean scientists and their students, and provides valuable training for students and technicians in the fields of ecology, environmental biology, environmental management and conservation, and global change.
