Between the tides: The impact of human exploitation on an intertidal ecosystem, Mozambique

This research project was born as one of the research lines in ecology at the Eduardo Mondlane University. The research was carried out in the framework of the Deibi-project (Desenvolvimento de Ensino c de Investicao na area de Biologia), which started in 1991. This project was managed by the University of Groningen, with funding from Nuffic, in an effort to strengthen the Department of Biological Sciences of the Eduardo Mondiane University. A first step towards the research presented here, was made in 1993 when we started to investigate the impact of people on the intertidal ecosystem. This preliminary study (see chapter eight) showed us how complex the whole situation really was, and made it clear to us that more intensive research activities were indispensable A project proposal was therefore written (de Boer 1997), based on the results of the backstop mission carried out by Prof. Dr. H.H.T Prins. Besides the scientific significance, the research project enhanced the training capacity of the Biology Department. Students could be trained in a multidisciplinary research project, and the practical experience could be essential for future employment. The ecosystem analysis could also be useful for other coastal areas in Mozambique. The theoretical background for conservation studies and for environmental impact assessment studies will thereby be strengthened (see Andersson and Ngazi 1995; Dayaratne et al. 1995b). The intertidal area of Inhaca is intensively used by the local population. Women search for crabs and shellfish, and men fish during high and low water. The recent decrease in abundance of sea cucumbers and Tridacna shells around Inhaca (own observation, but see also Gujral 1995) is one of the indications that exploitation could change the intertidal ecosystem. Since the peace agreements after the civil war (1978-1992), economic activities have been initiated everywhere and an 800 million US$ development project has been planned for Inhaca and surrounding areas. The coastal zone of Mozambique, in combination with its location close to South Africa, offers opportunities for the development of tourist activities. The Ministry of Environmental Coordination is currently evaluating numerous project proposals together with environmental impact assessments for activities in fragile ecosystems with mangroves and corals in the coastal area of Mozambique. Management and conservation plans have to be made, but these need to be based on sound understanding of the structuring forces of the ecosystems. Moreover, the functioning of the ecosystem and its reaction to human disturbance should be known. Unfortunately, the structuring forces of ecosystems are poorly under- stood. Women collect mainly predatory crab from the area, such as the mudcrab Scylla serrata and the blue swimming crab Portunus pelagica. Abundant predators are regarded as potential keystone species (Menge et al. 1994, see below). So, through the removal of these predators, people could alter the intertidal community. The abundance of the predators could decrease, and populations of prey species of these crabs could grow due to the de- crease in predation pressure. The study concentrated therefore on the analysis of the intertidal community structure, and the potential impact people could have through their exploitation.