Ecotones, or boundary zones between land and inland waters (such as lakes, streams and rivers), are the principal routes for transport of organic matter and nutrients across landscapes via physical and biological vectors. The ecotone is the place of cumulation and transformation of in situ production as well as of allochthonous material from adjacent aquatic and terrestrial systems. The ecotype functions as an important barrier or filter for principal nutrients, such as phosphorus and nitrogen, responsible for the eutrophication and degradation of surface waters. Intensive forest cutting, agriculture, pollution and bank regulation, urbanization and hydrotechnical constructions seriously endanger the ecotone systems and damage their protective function. It is vital to develop a scientific understanding of the behaviour of phosphorus and nitrogen in these transitional boundary habitats. Such an understanding is important for the rational protection, management and restoration of ecotones connected with lakes and rivers. The importance of nutrient cycling and retention is discussed from the point of view of ecotone function, management and reconstruction in order to sustain its protective role for water bodies. Various types of land/water transitory zones are discussed: wetlands, lake littoral systems, riparian zones of rivers, streams and brooks, the contact zones between groundwater and surface waters of lakes and rivers, air--water interfaces, and patch/ecotone structures in watersheds.

Lake Titicaca, because of its area and volume and its situation at high attitude within the tropics, is a unique hydrological site in the world. It should be noted that it stands at the transition point between two very distinct geographical regions: the desert fringe of the Pacific coast to the west and the great Amazonian forest extending to the Atlantic coast to the east. Many scientists have been attracted to the lake in the past because of its unusual limnological features. In this book the editors have compiled an exhaustive review of current knowledge from the existing literature and from the results of more recent observations. It is certain that this book will become the essential reference work for scientists wanting to make progress in revealing the lake's secrets. It can be stated unequivocally that this work constitutes a complete review of the present state of knowledge on Lake Titicaca and that it provides the latest results of research on this habitat.

Biodiversity, sometimes simply understood as "diversity of species", is a specific quality of life on our planet, the dimensions and importance of which have just lately been fully realized. Today we know that "biological diversity is a global asset of incalculable value to present and future generations" (Kofi Annan). Biodiversity is spread unequally over the world: in fact, the main share of biological resources worldwide is harboured predominantly by the so-called developing countries in the tropics and sub tropics. Therefore, Biodiversity - A Challenge for Development Research and Policy was chosen as the title for an international conference which was held in Bonn in 1997 as one of the first major events organized by the then newly established North-South Centre for Development Research (ZEF) at Rheinische Friedrich-Wilhelms-Universitat Bonn (Germany). Since the ZEF, founded by the Senate of the University of Bonn in 1995, has played a central role in turning Bonn into a centre for international cooperation and North-South dialogue. The Centre is a product of the Bonn Berlin agreement of July 1994 which was adopted to offset the effects caused by the Parliament and much of the Government moving to Berlin. It fits in well with the double strategy to strengthen Bonn's position as an interna tional science arena and as an eminent place for development policy and the national and supranational agencies dealing with this issue.