The Environmental Pros and Cons of Damming Rivers for Hydropower, and Nut Allergies in Children
Dear EarthTalk: What are the environmental pros and cons of damming rivers for hydropower?
Kartikeya Singh, Greenville, South Carolina
Hydropower electricity generated from turbines churning in dammed rivers has been part of AmericaÃs energy mix since the 1880s when the worldÃs first hydroelectric plant began operation on the Fox River in Appleton, Wisconsin. By the 1940s, hydropower accounted for about 40 percent of AmericaÃs energy needs.
Hydropower today accounts for only about 10 percent of electricity generation in the U.S., but it plays a crucial role in keeping regional economies afloat, such as in parts of the Pacific Northwest where dammed rivers provide 80 percent of the electricity needed by area residents and businesses.
Many environmentalists still cheer hydropower as the only major source of electricity that is renewable and non-polluting. Unlike energy generated from fossil fuels, hydropower plants do not emit the waste heat and gases that are major contributors to air pollution, global warming and acid rain. Nor do they require the environmentally destructive mining and drilling needed to acquire coal, natural gas and oil.
Another environmental benefit of hydropower is its ability to help control otherwise wide fluctuations in water flow in and around rivers. By increasing water flow during dry months and reducing flow during periods of heavy run-off, hydropower projects help to enhance aquatic habitats while preventing damage to vegetation and wildlife along stream banks.
Despite the benefits, however, hydropower does have its environmental costs. In general, damming rivers and installing hydropower turbines permanently alters the environment and disrupts naturally functioning ecosystems. For example, populations of wild salmon and trout which migrate back and forth between upstream spawning grounds and the ocean have fallen off by as much as 90 percent in parts of the U.S. due to the damming of major coastal area rivers for hydropower.
Last year, one of MaineÃs major utilities agreed to remove three dams on the Penobscot River and its tributaries in order to restore declining populations of wild Atlantic salmon. Environmentalists are calling for similar measures in the Pacific Northwest to save dwindling populations of Coho and Chinook salmon.
As more harmless forms of renewable energy such as solar, wind and hydrogen become more economically viable, hydropower will likely play an increasingly smaller role in America's energy mix. Indeed, only time will tell whether these more efficient sources of renewable energy might finally end the need for hydropower while making fossil fuels obsolete as well.
Dear EarthTalk: WhatÃs behind the startling explosion in nut allergies among children? Is it changes in the kids, the peanuts or the processing?
Lynne Whetzel, Ithaca, NY
Recent research does in fact show that the incidence of nut allergies among American and British children has tripled within the last two decades. No one knows for sure why, but because the phenomenon seems to be occurring only in developed countries, some environmentalists believe that pollution and synthetic chemicals might be to blame. An allergic reaction happens when the bodyÃs immune system overreacts to a perceived threat, and researchers believe there may be an as-yet undiscovered link between exposure to various chemicals, pollutants and food additives and an overall rise in immune system disorders.
Parents of children suffering from nut allergies live life constantly checking the ingredients on food labels. Nuts and nut oils are used in an increasingly wide range of processed foods, including many of the chips and cereals preferred by kids today. The ubiquity of snack foods throughout our society makes it difficult for kids to avoid nuts and nut oils, even if they know they are allergic.
Nut allergies can start early on and usually do not go away in adulthood. >From the second trimester of pregnancy on, the unborn fetus can recognize allergens to which the mother has been exposed, and may at this early point begin to develop sensitivities that can lead to allergic reactions following birth. Pregnant women with a history of allergic reactions can minimize the risk to their children by avoiding certain known allergens, especially tree nuts (cashews, almonds, pecans and walnuts) and peanuts. Breast-feeding mothers should also avoid foods that contain these allergens, as they can be transmitted to babies via breast milk. Additionally, several leading brands of creams used by mothers to ease discomfort while breast-feeding contain nut oils which can trigger allergic reactions in babies as well.
Symptoms of nut allergies, as with many allergies, can range from mild reactions like watery eyes, an itchy throat or a runny nose, to severe reactions like eczema, hives, nausea and vomiting. In extreme cases, allergic reactions can lead to anaphylaxis, a life-threatening condition hastened by the bodyÃs release of toxic amounts of histamine into the blood stream.
The Fairfax, Virginia-based Food Allergy & Anaphylaxis Network is a non-profit organization that raises awareness about and conducts research on food allergies and anaphylaxis. The organizationÃs diverse membership makes it the leading clearinghouse on food allergies in the U.S. Meanwhile, the Farnborough, England-based Anaphylaxis Campaign provides similar services in the U.K. and beyond. These groups can be invaluable to families struggling through food allergies.
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