Water for people.pdf - WHO Thailand Digital Repository

1 5 0 / C H A L L E N G E S T O L I F E A N D W E L L - B E I N GProtecting Ecosystems for People and PlanetRestoration of degraded systemsIncreasing recognition of deterioration in a range of ecosystems hasled to a growth of interest in the science and practice of ecologicalrestoration. The main aim is to re-establish the key characteristics ofan ecosystem, such as composition, structure and function, whichwere present prior to degradation.Many restoration projects have now been initiated in differentparts of the world, focusing on a variety of ecosystem types, includingfreshwaters. Many projects are being undertaken by non-governmentalorganizations (NGOs), often as community-based initiatives. It is widelyanticipated that restoration will become a central activity inenvironmental management in the future. Such efforts are beingsupported by development of national and international policies – forexample, they are explicitly recommended in Article 8f of the UNConvention on Biological Diversity, which states that parties should‘rehabilitate and restore degraded ecosystems and promote therecovery of threatened species, through the development andimplementation of plans or other management strategies’.Depending on the nature of the disturbance, even heavilymodified waters can in some circumstances recover if the source ofimpact is removed. This applies to river systems in particular,perhaps because of their dynamic nature, with inherent hydrologicalvariability, and the consequent need for flexibility and colonizationability among their biological communities (see box 6.7).The term ‘restoration’ may be applied to a range of measures thatdiffer greatly in spatial scale and complexity. Most schemes to datehave involved enhancement of water quality, often by controllingpoint source pollution in rivers or lakes, or enhancing geomorphic orhabitat conditions along a river reach. In principle, a series of smallscaleprojects could be coordinated in order to meet restoration goalswithin an entire catchment, but this would require a wider scientificbase and wider participation than anything yet achieved.Some recent interest has focused on the physical removal ofdams and related engineering structures. In some cases it has beenshown that there is a greater long-term economic benefit to begained from removing a dam and restoring fishery and amenityvalues, than from maintaining the dam, particularly where fishpassage must be provided. However, several high-profile cases showthat agreeing on and implementing a plan for dam removal can becontentious. A significant number of dams have recently beenremoved or are likely to be removed soon. Most such events haveoccurred in developed countries, mainly in North America andEurope (see box 6.8), and most of the dams have been small runof-riverimpoundments (not hydroelectric). This phenomenon hasbecome so important that the actual removals may have outpacedgrowth of the scientific understanding needed to manage theconsequent ecological changes.There is a large and increasingly accessible literature availableon restoration of rivers (e.g. Nijland and Cals, 2001) and wetlands(Interagency Workgroup on Wetland Restoration, n.d.). Several worksare in ‘toolkit’ form in order to assist locally based initiatives(Environment Agency, 2001).Box 6.7: The ‘Green Corridor’: floodplainrestoration along the Danube ValleyMore than 80 percent of wetlands along the Danube Riverhave been destroyed since the start of the twentiethcentury. Working with Romania, Bulgaria, Moldova and theUkraine, WWF is developing a series of projects tomaintain existing wetland protected areas, create newones and reconnect the remnant marshlands and otherwetlands. This is the largest international wetlandrestoration and protection initiative in Europe, and isintended to restore the Danube’s natural capacities forpollution reduction, flood retention and natureconservation for the benefit of local people andecosystems of the Danube River and Black Sea.Box 6.8: The Edwards damThe Edwards hydroelectric dam on the Kennebec River,Maine (United States), was removed in 1999 following aruling by the Federal Energy Regulatory Commission thatthe environmental benefits of removal outweighed theeconomic benefits of continued operation andmaintenance. It had been in place for more than 160years. A year after removal, migratory fishes includingAtlantic salmon Salmo salar and alewife Alosapseudoharengus had returned to reaches above the damsite. In addition, water quality had improved, and both thebiodiversity of aquatic invertebrates and recreational useof the river increased.Source: WWF at http://www.panda.org/livingwaters/danube/index.cfm.Source: Natural Resources Council of Maine.