Estuaries: A Lifeline of Ecosystem Services in the Western Indian Ocean

Abstract

It is in estuaries and deltas where the richness of the land meets the abundance of the sea, creating an environment of high diversity, dynamism and productivity. Nevertheless, the important contributions estuaries make to local livelihoods and national economies, as well as to their complex role in the functioning of the land-ocean interface, are often overlooked. The Western Indian Ocean is dotted with important estuaries and deltas, including the Tana and Sabaki in Kenya, Pangani, Rufiji and Ruvuma in Tanzania, Zambezi, Incomati, Maputo, Pungwe and Limpopo in Mozambique, Thukela in South Africa and Betsiboka in Madagascar. With numerous plans and investments in place for a massive acceleration in infrastructure development and energy and food production, human activities will increasingly impact these important estuarine and coastal ecosystems and the life-supporting services they provide. In this regard, the unique, diverse and productive estuaries and deltas of the Western Indian Ocean stand at a crucial crossroad. The Western Indian Ocean is internationally recognized as a hot spot of biodiversity, hosting one-third of the 38 globally, recognized marine and coastal habitats, an abundance of fish species and marine mammals, all five marine turtle species, over 40 species of seabirds and the longest fringing reef in the world. The region is also home to the charismatic coelacanth, nicknamed the living fossil, and the critically, endangered sawfish and seahorse. Furthermore, the region’s coastal and marine waters are important fishing grounds, supporting the livelihoods of the local population. Its marine parks and other protected areas are also the basis for an active tourism industry The unfortunate reality, however, is that human activities in these river catchments are having increasingly serious impacts on these sensitive downstream estuarine and coastal ecosystems. The damming of rivers over the past 50 years, combined with reduced rainfall, expansion of irrigated agriculture and other increasing water abstraction and land uses within various catchments, are among the underlying causes of those changes. Furthermore, pollution from municipal and industrial effluents is exacerbating the serious degradation of waters and sediment quality that is being observed in these rivers, estuaries and coastal waters, resulting in a loss of biodiversity, increasing eutrophication and reduced fish catches in many locations in the Western Indian Ocean. To set the stage for addressing the continuing degradation of these important land-sea interfacing water systems, this publication was made possible due to the leadership of four scientists: Prof. Salif Diop from the University of Dakar; Dr. Peter Scheren from WWF; Prof. John Machiwa from the University of Dar es Salaam and Prof. Jean-Paul Ducrotoy from the Institute of Estuarine and Coastal Studies, The University of Hull, UK. The focus of this book is on estuaries, but its scope and implications extend well beyond this particular coastal feature. Indeed, estuaries can only be considered as part of the life cycle of the entire river basins draining into them and the downstream marine areas that receive these riverine inputs. These interlinked systems and the life-supporting ecosystem services they provide are particularly sensitive to human and natural pressures; hence the title of this book “Estuaries: a Lifeline of Ecosystem Services in the Western Indian Ocean”. It is our belief that this book will be a valuable source of information and guidance for the numerous scientists, researchers, managers and decision makers concerned with the integrated management of estuaries, deltas, lagoons, and the coastal and marine areas of the Western Indian Ocean and will help facilitating their sustainable use.