Introduction

In Module 1, you were introduced to some of the large-scale or long-term factors affecting the development of tropical forests around the world. We looked at how forests might have developed over the geological time-scale, and at processes such as evolution. In this module, we continue to look at the environmental factors that affect forests, but deal with processes operating on much shorter time-scales. Factors such as climate, soil type and water availability all affect the species composition of forests, principally by affecting the composition and structure of the vegetation. The nature of the vegetation in turn affects the composition and structure of the animal communities present in the forest.

Understanding the role that these factors play is important but quite difficult. This is because of the number of links within the ecosystem. For example, while the vegetation affects the number of niches available, for example, to birds, the birds may affect the vegetation through their role in pollination and seed dispersal. This is sometimes described as a delicate balance but, as we shall see as we progress through this and the accompanying course (“Ecological processes in tropical forests”), it is less of a balance than a continuous interplay amongst the different ecosystem components, with some relationships being fairly transient and others more permanent.

Understanding these relationships is important as when one aspect of the ecosystem is affected, there may be knock-on effects for many other components. Unravelling this complex web of relationships presents huge challenges and there are many unknowns. This module will introduce you to some of these complexities.