To create safe and comfortable living quarters, beavers bring down trees, fashion them into sticks and logs, and build dams. In the process, they flood the surrounding terrain, drown local vegetation, and force burrowing critters to higher ground. Humans occasionally do the same for similar reasons, but of course on an industrial scale. The bigger the dam, the greater the impacts. Obviously.
A comprehensive report published in 2000 by the The World Commission on Dams details these impacts – as well as the costs, benefits and misconceptions associated with the construction of large dams. The report looks at large dams intended for irrigation, flood control and electricity generation worldwide. Its findings should be familiar to anyone who has been directly affected by a hydro electric development.
With respect to construction, the report found that large dams “have a marked tendency towards schedule delays and significant cost overruns.”
With respect to social impacts, planners and decision-makers “have often neither adequately assessed nor accounted for the adverse social impacts of large dams. As a result, the construction and operation of large dams has had serious and lasting effects on the lives, livelihoods and health of affected communities, and led to the loss of cultural resources and heritage”.
The report noted that “sedimentation and the consequent long-term loss of storage is a serious concern globally”. With respect to safety, “of dams built before 1950, 2.2% failed, while the failure rate of dams built since 1951 is less than 0.5%”.
The report summarized environmental impacts thus:
- 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;
- emissions of greenhouse gases from reservoirs due to the rotting of vegetation and carbon inflows from the basin;
- the loss of aquatic biodiversity, upstream and downstream fisheries and the services of downstream floodplains, wetlands and riverine estuarine and adjacent marine ecosystems;
- the creation of productive fringing wetland ecosystems with fish and waterfowl habitat opportunities in some reservoirs; and
- cumulative impacts on water quality, natural flooding, and species composition where a number of dams are sited on the same rivers.
In conclusion, the report presented seven strategic priorities for future dam development that could “achieve equitable and sustainable outcomes, free of the divisive conflicts of the past”.
Meanwhile, dams continue to be built to satisfy the ever-rising demand for electricity, especially in countries experiencing rapid modernization. In China, the Three Gorges hydroelectric dam, the world’s largest, flooded about 632 square kilometres of the Yangtze River valley and forced the resettlement of over a million people living in hundreds of towns and villages. The dam now impedes the normal flow of silt down the Yangtze, leaving it to settle in the Three Gorges dam reservoir and changing riverbed and flood plane dynamics downstream.
The earth has more or less been able to absorb the impacts of such industriousness, but the human beneficiaries have had to deal with ethical and economic conflicts. On one hand, they get low-cost, reliable, and relatively pollution-free electricity for their homes and factories. On the other, they can lose significant geographical, economic, cultural, and even personal assets.
So it goes without saying that all electricity produced this way comes with a loss. The same can be said about the development of the human built environment in general. Plant and animal life of every size and species is pushed aside by human enterprise – whether it plays out in your vegetable garden or in hundreds of square kilometres of countryside. The landscape is changed.
Needless to say, human impacts on the environment are a political headache. Politicians must, as best they can, referee economic maneuvers instigated by industrial interests who, in turn, cater as best they can to the growing appetites of exploding populations. In doing so, they are squeezed by the seemingly intractable, conflicting ethics that underpin industrial exploitation of the earth. So justifiably some of us will always be deeply disturbed by our economic achievements.
It would appear that the impulse to mould the earthly environment to our liking is part of human nature. The problem may simply be that there are far too many of us involved in the venture. We are bursting our terrestrial seams – which is to say that the international community probably needs to give some serious thought to population control.
Featured image: The Diablo Dam on the Skagit River, Washington State.