69. How Predictable Are Ecological Communities

Up to this point, we have examined how factors affecting population growth, ecological interactions, and the flow of energy and resources in ecosystems help account for the abundance and distribution of species. This lecture begins by pointing out that even complete knowledge of all these factors cannot fully explain abundance and distribution, because of the importance of history and chance. Two distinct views of how ecological communities develop over timeone emphasizing predictability and the other emphasizing chancecompeted for several decades until experiments demonstrated the key role of chance events in determining how communities change over time. As a result, ecologists now emphasize the importance of studying patterns of disturbance in communities instead of trying to predict the endstate of ideal communities.