What is new about risks in the 21st century? Recent years have witnessed a host of large-scale disasters of various kinds and in various parts of the world: hugely damaging windstorms and flooding in Europe and ice storms in Canada; new diseases infecting both humans (AIDS, ebola virus) and animals (BSE); terrorist attacks such as those of September 11 in the US and the Sarin gas attack in Japan; major disruptions to critical infrastructures caused by computer viruses or simply technical failure, etc. It is not just the nature of major risks that seems to be changing, but also the context in which risks are evolving as well as society's capacity to manage them. This book explores the implications of these developments for economy and society in the 21st century, focusing in particular on the potentially significant increase in the vulnerability of major systems. The provision of health services, transport, energy, food and water supplies, information and telecommunications are all examples of vital systems that can be severely damaged by a single catastrophic event or a chain of events. Such threats may come from a variety of sources, but this publication concentrates on five large risk clusters: natural disasters, technological accidents, infectious diseases, food safety and terrorism. This book examines the underlying forces driving changes in these risk domains, and identities the challenges facing OECD countries- especially at international levels- in assessing, preparing for and responding to convention and newly emerging hazards of this kind. It also sets out a number of recommendations for governments and the private sector as to how the management of merging systemic risks might be improved.