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Megadams: a destructive energy source
While sometimes presented as sustainable energy sources, large-scale hydroelectric dam projects (so called ‘mega dams’) are highly destructive and not compatible with tackling climate change. The dam industry has choked more than half of the world’s major rivers with around 50,000 large dams, many of which are hydro-electric projects. The consequences of this massive engineering programme have been devastating: wiping out species; flooding huge areas of wetlands, forests and farmlands; displacing tens of millions of people and destroying their livelihoods, often with little or no compensation or reparations; and leaving the planet’s freshwaters in far worse shape than any other major ecosystem type, including tropical rainforests. Furthermore, plans for the construction of many new mega dams are underway in many parts of the world.
Dams are the largest single anthropogenic source of methane, mainly from the rotting vegetation that dams collect, being responsible for around 23 per cent of all methane emissions due to human activities, and 4-5 per cent of all human-caused warming. Methane is a much more potent heat-trapping gas than carbon dioxide, although it does not last as long in the atmosphere. Mega dams also disrupt water and sediment flow which reduces biodiversity and blocks fish migration. Dams and river diversions are the main reason why one third of the world’s freshwater fish species are extinct, endangered or vulnerable. Many shellfish, amphibians, plant and bird species that depend on freshwater habitats are also extinct or at risk.
The construction of mega dams is associated with the forced displacement of communities and devastating social impacts. In 2000 the World Commission on Dams concluded that between 40 and 80 million people worldwide had been physically displaced by dams. People displaced by dams lose their land and livelihoods and are frequently forced onto resettlement sites where they are often not provided with basic services like water, food or sanitation. Compensation is rarely provided, or is often inadequate, with communities forced to break up and displaced families facing poverty and destitution as migrant labourers or slum dwellers.
As with other destructive energy sources, the construction of dams and the removal of affected communities is often accompanied by significant repression and violence. One of the worst human rights atrocities associated with dams occurred in Guatemala in the 1980s when more than 440 Maya Achí Indigenous People, mainly women and children, were murdered by paramilitaries because they refused to leave their ancestral lands for the World Bank-funded Chixoy Dam. Survivors of the massacre are still fighting for reparations for their suffering.
Changes in river flow resulting from dam construction also impact negatively on the lives of millions of people living downstream from dams, leading to declines in fisheries, poor water quality and disruption of the annual floods essential for the irrigation of agricultural land, thus threatening local, regional and national food security.
Despite all of these negative impacts, mega dams are considered a solution to the climate crisis by the UN, and their construction is encouraged by the UN’s ‘Clean Development Mechanism’ (CDM). A carbon trading and offsetting mechanism and false solution to the climate crisis, the CDM allows highly polluting, industrialised countries to avoid reducing their greenhouse gas emissions by paying developing countries to invest in energy sources that supposedly reduce their emissions, but in reality lock them in to destructive energy sources and create perverse incentives to create more emissions.