This book incorporates twenty contributions on diverse aspects of the environmental geochemistry in tropical and sub-tropical environments, drawing together extensive original research not readily available elsewhere. Coverage includes intercontinental comparisons drawn on paleoclimatology, environmental impacts of mining and geochemistry of continetal shelf sediments.

The last few decades have seen a rapid growth of interest in the mangrove ecosystems. This is due, on the one hand, to the perception that mangrove ecosystems are valuable resources, and, on the other hand, due to vested economic interests. There is an accelerated rate of destruction of mangroves worldwide. Almost all nations of the world tropical belt are concerned with the conservation of this natural wealth, but surreptitiously permit the misuse of mangroves for quick monetary returns unabatedly. The scientific community and decision makers of many nations are now in a state of alert, requesting sound directives for the sustainable use of mangroves worldwide. The present publication is an attempt to present in an organized manner the present state of knowledge which could be useful for decision makers and of interest to all those who see the ecological and economical potential of the various types of mangrove ecosystems.

Three symposia on environmental geochemistry in tropical countries, held in Niter6i, Brazil (1993), in Cartagena, Colombia (1996) and in Nova Friburgo, Brazil (1999), made it very clear that tropical geochemistry is of world standard and fast increasing in multi disciplinarily and impact on important geochemical paradigms. It has additionally strong links with the economy of tropical countries, such as mining and industrialisa tion and is in full development for treating environmental problems caused by human activities of urban or industrial origin. We must compliment Prof. Jorge Abriio and his colleagues in Brazil and Dr. Gloria Prieto and her colleagues in Colombia for these ini tiatives. The participation of respectively 180 and 150 scientists, coming from 15 different countries for the first and second symposia, has shown that a large interest exists for tropical environmental geochemistry. It also demonstrates the necessity to understand tropical environmental problems. The organisation of a large international symposium is not possible without the assistance of state and federal authorities, for which those of Brazil and Colombia have to be complimented. The 3rd Symposium on Environmental Geochemistry in Tropical Countries was the last of the series and was attended by 22 countries and 170 participants and treated a number of related environmental and economic problems."

Protection of the environment has nowadays become a major challenge and a condi tion for survival of future human generations and life on Earth in general. Yet it is still far too much of a dream or hope rather than a reality in the policy of our societies. Presently we are experiencing an unprecedented exponential growth of demography combined with a race for profit, resulting in excessive consumption particularly of en ergy, and a serious impact on the world ecosystems. Various types of pollutants and emerging new diseases not only disrupt the normal course of life, but also above this some of the atmospheric pollutants are most likely involved in the changing climate. We fear and literally shiver at the thought that the "changing climate" would ultimately disrupt the fragile thermodynamic equilibrium between the atmosphere and the oceans. Are we insensitive to these facts to the point of pushing our descendants, some genera tions ahead, into a new glacial period after a first period of warming up, at least, in northern Europe, like the one that took place 13 to 14 millennia ago? Surely the planet's nature is not prepared to be dominated by man and will go its way, whether humanity will be alive or dead."