Water for people.pdf - WHO Thailand Digital Repository

P R O T E C T I N G E C O S Y S T E M S F O R P E O P L E A N D P L A N E T / 1 3 3Table 6.2: Pressures on freshwater ecosystemsHuman activity Potential impact Function at riskPopulation and consumption Increases water abstraction and acquisition of cultivated land Virtually all ecosystem functions including habitat, productiongrowth through wetland drainage. Increases requirement for all other and regulation functionsactivities with consequent risksInfrastructure development Loss of integrity alters timing and quantity of river flows, Water quantity and quality, habitats, floodplain fertility, fisheries,(dams, dikes, levees, water temperature, nutrient and sediment transport delta economiesdiversions)and thus delta replenishment, blocks fish migrationsLand conversion Eliminates key components of aquatic environment, loss of Natural flood control, habitats for fisheries and waterfowl,functions; integrity, habitat and biodiversity, alters runoff recreation, water supply, water quantity and qualitypatterns, inhibits natural recharge, fills water bodies with siltOverharvesting and exploitation Depletes living resources, ecosystem functions and biodiversity Food production, water supply, water quality and water quantity(groundwater depletion, collapse of fisheries)Introduction of exotic species Competition from introduced species alters production and Food production, wildlife habitat, recreationnutrient cycling, and causes loss of biodiversity amongnative speciesRelease of pollutants to land, Pollution of water bodies alters chemistry and ecology of Water supply, habitat, water quality, food production. Climateair or water rivers, lakes and wetlands. Greenhouse gas emissions change may also impact hydropower, dilution capacity, transport,produce dramatic changes in runoff and rainfall patterns flood controlA wide range of human uses and transformations of freshwater or terrestrial environments has the potential to alter, sometimes irreversibly, the integrity of freshwater ecosystems.Source: IUCN, 2000.Box 6.1: Draining wetlands for malaria control: a conflict of interests?With the 1898 discovery that anopheline mosquitoes alonetransmitted the malaria parasite (and, about the sametime, the discovery of other mosquito genera and vectorbornediseases) a period of disease control activitiesstarted focusing on ‘source reduction’. By eliminating theaquatic breeding habitats of mosquitoes, their populationdensities were reduced and disease transmissioninterrupted. Anticipating later integrated rural developmentapproaches, malariologists, engineers and agronomistscollaborated to reduce the disease burden and promoteagricultural development at the same time. The drainage ofthe Pontine Marshes near Rome in the 1930s remains themost well-known example, though it remains smallcompared to what colonial governments achieved in, forexample, India, the Malaysian peninsula and Indonesia. Theadvent of residual insecticides put an end to this approach.From today’s perspective, with the high value given towetlands, such an approach to disease control isinconceivable. Yet the conflict of interest between humanhealth and environmental integrity needs to be assessedfor each specific location. To start with, wetland drainagewould not, generally, be the practice of choice in Africasouth of the Sahara, where the world’s main malariaburden (90 percent) persists. The local vector species isecologically too versatile and transmission patterns toointense to be influenced by reducing the density ofmosquito population alone. In other parts of the world, thetrade-offs between impacts on the environment of limiteddrainage (or other interventions in the hydrology) and ofthe recurrent use of insecticides as mainstay interventionswill need to be assessed locally. Wetland communities willneed to be protected by specially targeted interventions formalaria control such as placing mesh screens in housewindows, doors and eaves, and the intensified use ofmosquito nets. Also, in an environment with an increasedmalaria risk, access to health services, often already moredifficult in wetland areas, will need to be greatly facilitatedto allow for early detection and treatment.