The purpose of this introduction is to provide a background to the natural and human environmental systems on the Austral-Asian (or PEP II) transect. Aspects of these systems are discussed in greater detail in the papers that follow in this volume. Focusing on the distinctive characteristics of the PEP II transect, this paper begins with an overview of the main physical features, reviews the nature of the present climate systems and concludes with an Outline of the patterns of human settlement across the region and the diversity of environmental interactions between these and human societies. (C) 2003 Elsevier Ltd and INQUA. All rights reserved.