The World Commission on Dams (WCD) released its report on November 2000, after having carried out detailed studies and surveys on a number of large dams throughout the world. What follows are quotes from the sections "People and Large Dams" and "Ecosystems and Large Dams." The full report --in several languages-- is available at: http://www.dams.org/report/
"In terms of the social impacts of dams, the Commission found that the negative effects were frequently neither adequately assessed nor accounted for. The range of these impacts is substantial, including on the lives, livelihoods and health of the affected communities dependent on the riverine environment:
- Some 40-80 million people have been physically displaced by dams worldwide
- Millions of people living downstream from dams - particularly those reliant on natural floodplain function and fisheries - have also suffered serious harm to their livelihoods and the future productivity of their resources has been put at risk
- Many of the displaced were not recognised (or enumerated) as such, and therefore were not resettled or compensated
- Where compensation was provided it was often inadequate, and where the physically displaced were enumerated, many were not included in resettlement programmes
- Those who were resettled rarely had their livelihoods restored, as resettlement programmes have focused on physical relocation rather than the economic and social development of the displaced
- The larger the magnitude of displacement, the less likely it is that even the livelihoods of affected communities can be restored
- Even in the 1990s, impacts on downstream livelihoods were, in many cases, not adequately assessed or addressed in the planning and design of large dams
In sum, the Knowledge Base demonstrated a generalised lack of commitment or lack of capacity to cope with displacement. In addition, large dams in the Knowledge Base have also had significant adverse effects on cultural heritage through the loss of cultural resources of local communities and the submergence and degradation of plant and animal remains, burial sites and archaeological monuments.
The Knowledge Base indicated that the poor, other vulnerable groups and future generations are likely to bear a disproportionate share of the social and environmental costs of large dam projects without gaining a commensurate share of the economic benefits:
- Indigenous and tribal peoples and vulnerable ethnic minorities have suffered disproportionate levels of displacement and negative impacts on livelihood, culture and spiritual existence
- Affected populations living near reservoirs as well as displaced people and downstream communities have often faced adverse health and livelihood outcomes from environmental change and social disruption
- Among affected communities, gender gaps have widened and women have frequently borne a disproportionate share of the social costs and were often discriminated against in the sharing of benefits
Where such inequities exist in the distribution of the costs and benefits, the Global Review emphasises that the 'balance-sheet' approach to adding up the costs and benefits is increasingly seen as unacceptable on equity grounds and as a poor means of choosing the 'best' projects. In any event, the true economic profitability of large dam projects remains elusive, as the environmental and social costs of large dams were poorly accounted for in economic terms.
More to the point, failures to account adequately for these impacts and to fulfil commitments that were made have led to the impoverishment and suffering of millions, giving rise to growing opposition to dams by affected communities worldwide. Innovative examples of processes for making reparations and sharing project benefits are emerging that provide hope that past injustices can be remedied and future ones avoided."
Regarding the environmental impacts of large dams, the report states:
"The generic nature of the impacts of large dams on ecosystems, biodiversity and downstream livelihoods is increasingly well known. From the WCD Knowledge Base it is clear that large dams have led to:
- the loss of forests and wildlife habitat, the loss of species populations and the degradation of upstream catchment areas due to inundation of the reservoir area
- the loss of aquatic biodiversity, of upstream and downstream fisheries, and of the services of downstream floodplains, wetlands, and riverine, estuarine and adjacent marine ecosystems; and
- cumulative impacts on water quality, natural flooding and species composition where a number of dams are sited on the same river
On balance, the ecosystem impacts are more negative than positive and they have led, in many cases, to significant and irreversible loss of species and ecosystems. In some cases, however, enhancement of ecosystem values does occur, through the creation of new wetland habitat and the fishing and recreational opportunities provided by new reservoirs.
The Commission found that reservoirs sampled so far by scientists all emit greenhouse gases, as do natural lakes, due to the rotting of vegetation and carbon inflows from the catchment. The scale of such emissions is highly variable. Preliminary data from a Case Study hydropower dam in Brazil show that the gross level of these emissions is significant, relative to emissions from equivalent thermal power plants.
However, in other reservoirs studied (notably those in boreal zones), gross emissions of greenhouse gases are significantly lower than the thermal alternative. A full comparison would require measurements of the emissions from natural pre-impoundment habitats. More research is needed on a case-by-case basis to demonstrate the capacity of hydropower to offset climate change.
Efforts to date to counter the ecosystem impacts of large dams have met with limited success due to the lack of attention to anticipating and avoiding such impacts, the poor quality and uncertainty of predictions, the difficulty of coping with all impacts, and the only partial implementation and success of mitigation measures. More specifically:
- It is not possible to mitigate many of the impacts of reservoir creation on terrestrial ecosystems and biodiversity, and efforts to 'rescue' wildlife have met with little long-term success
- The use of fish passes to mitigate the blockage of migratory fish has had little success, as the technology has often not been tailored to specific sites and species
- Good mitigation results from a good information base; early co-operation between ecologists, the dam design team and affected people; and regular monitoring and feedback on the effectiveness of mitigation measures
- Environmental flow requirements (which include managed flood releases) are increasingly used to reduce the impacts of changed streamflow regimes on aquatic, floodplain and coastal ecosystems downstream
Given the limited success of traditional mitigation measures, increased attention through legislation is now given to avoidance or minimisation of ecological impacts through setting aside particular river segments or basins in their natural state and through the selection of alternative projects, sites or designs. In addition, governments are experimenting with a 'compensatory' approach, offsetting the loss of ecosystems and biodiversity caused by a large dam through investment in conservation and regeneration measures and through protection of other threatened sites of equivalent ecological value.
Finally, in a number of industrialised countries, but particularly in the United States, ecosystem restoration is being implemented as a result of the decommissioning of large and small dams."
In general terms, the above findings reaffirm what local peoples and environmentalists have been suffering and denouncing for years. But the report's importance is that it now gives an official stamp of approval to those claims. We hope that this will signal the beginning of the end of large destructive dams which have resulted --as the report rightly states-- in "the impoverishment and suffering of millions."