The Niger River Basin, home to 100 million people, is a vital yet complex asset for West and Central Africa. It is the continent's third largest river basin, traversing nine countries -Benin, Burkina Faso, Cameroon, Chad, C©þte d'Ivoire, Guinea, Mali, Niger, and Nigeria. The River embodies both these nations' livelihoods and their geopolitics. It is not simply water but rather an origin of identity, a route for migration and commerce, a source of conflict, and a catalyst for cooperation. Cooperation among decision-makers and users is crucial to address the threats to water resources. The Niger.

Our understanding of the ecology of running waters has come a long way during the past few years. From being a largely descriptive subject, with a few under tones concerned with such things as fisheries, pollution or control of blackflies, it has evolved into a discipline with hypotheses, such as the River Continuum Concept (Vannote et a/. 1980), and even a book suggesting that it offers opportunity for the testing of ecological theory (Barnes & Minshall 1983). However, perusal of the literature reveals that, although some of the very early studies were concerned with large rivers (references in Hynes 1970), the great mass of the work that has been done on running water has been on streams and small rivers, and information on larger rivers is either on such limited topics as fisheries or plankton, scattered among the journals, or not available to the general limnologist. The only exceptions are a few books in this series of publications, such as those on the Nile (Rz6ska 1976), the Volga (Morduckai Boltovskoi 1979) and the Amazon {Sioli 1984), and the recent compendium by Whitton (1984) on European rivers, among which there are a few that rate as large.

As societies transition to evidence-based adaptation and management there is increasing recognition of the need for understanding climate change and variability dynamics and impacts at regional levels and for various activities. This book is a contribution toward that goal. Readers interested in climate change management will find detailed discussions of climatic variability dynamics in selected regions as well as new innovative ways of monitoring climate change, assessing climate risks, and predicting impacts. Those interested in refreshing the fundamentals of climate change and climate variability will find a very accessible review of the status of knowledge on the subject, including a balanced interrogation of available evidence. In an attempt to keep the book accessible, every effort was made to minimize technical jargon without compromising scientific accuracy. The result should be useful to researchers, practitioners, and policy makers.