Water-related ecosystem services
Water resources are essential for sustaining the life of humans and other living species on earth. Living organisms and ecosystems, however, face two distinct situations of water supply dynamics depending on the location and season. Many experience water shortage situations (at least seasonal scarcity), while others are endowed with water abundance throughout the year. Both situations often cause serious hardships to people and pressures on ecosystems supporting human life (i.e. drought and flooding) that need careful management for mitigation and prevention. Interference with natural water flows to reduce the direct effects of such undesirable phenomena, however, can disrupt ecosystem functions leading to negative consequences for human well-being, especially among the poor. The gains from interventions to regulate the hydrological cycle have often been achieved at high costs in terms of resulting ecological disruptions with major implications for human well-being. Like all other ecosystems, wetlands and freshwater systems provide multiple services to people and other life on earth (Fisher et al. 2008, Turner et al. 2000). Human actions altering natural systems to improve the provision of one or few components of the bundle of services provided by ecosystems often reduce the system’s capacity to provide other services (MEA 2005). Examples of tradeoffs in human–freshwater interactions are many and sometimes quite complex. Regulation of natural water flows through construction of dams and reservoirs to increase provision of water for irrigation, domestic and industrial use, flood protection and hydropower generation, for example, is known to have many negative ecological consequences. Habitat and biodiversity loss and widespread pollution are typical consequences of interventions to regulate natural water flows with many negative impacts on human well-being. Among the negative impacts of these ecological disruptions are fragmentation of aquatic habitats and consequent damages to fisheries, increased chemical pollution from irrigation agriculture and effluent discharge by industrial activities leading to loss of important health services and biological diversity, and disruption of provision of sediment and nutrient inputs to floodplains and the natural habitat for fish spawning and breeding (MEA 2005). It is therefore necessary to consider such important tradeoffs in ecosystem services for proper evaluation of the true costs and benefits to human well-being of water management strategies and policy interventions (Brouwer et al. 2003).