Battle over the Amazon: a giant dam generates controversy in Brazil's rainforest.
A battle is raging over a remote part of the Amazon rainforest in Brazil. The country s government has approved construction of an enormous hydroelectric dam called Belo Monte. The dam would divert the Xingu River, a tributary of the Amazon River, to generate electricity.
Brazil's economy has boomed in the past decade, increasing the demand for electricity. President Dilma Rousseff says that dams and the power they can generate are needed for continued growth.
But environmentalists around the world have joined with residents of the Amazon rainforest to try to halt the project. They say that damming the rainforest's rivers will have dire consequences--not only for Brazil, but for the entire planet.
A HIT TO THE RAINFOREST
At stake is the health of the Amazon, earth's largest rainforest. It stretches through eight countries and one territory and is home to about 400 indigenous groups.
The region is so important because it is a hotbed of biodiversity. It contains one out of every 10 of Earth's known species, with hundreds more being discovered each year.
The Amazon is also critical to health care. Scientists have studied only a fraction of the plant species found in the Amazon rainforest, but many of those plants have already led to medicines that treat diseases like cancer.
The huge rainforest also holds vast amounts of carbon dioxide that would be released into the atmosphere if it were deforested. That would accelerate global warming.
But the rainforest has already taken a hit. Over the past 40 years, nearly a fifth of the Amazon has disappeared because of logging and the clearing of land for agriculture.
Environmentalists say the Belo Monte Dam will make things even worse. The controversial hydroelectric dam, which would be the world's third largest in terms of the amount of electricity it generates, has an unusual design that could deliver a devastating one-two punch to the rainforest.
FLOODED AND PARCHED
A typical hydroelectric dam holds back water in a reservoir. The water then flows through turbines that generate electricity and into the river on the other side. Belo Monte, however, is designed as a two-part dam that opponents say would mean double trouble. The main dam would back up the Xingu's waters to form the reservoir, flooding an area roughly the size of Chicago and forcing thousands of people from their homes.
But instead of releasing the water along its natural course as most dams do, Belo Monte would divert most of the river's flow through artificial waterways to a second dam (see map, p. 11).
The problem with this diversion is that the water would bypass a 100 kilometer (62 mile) stretch called the Big Bend. That would leave fish like the zebra pleco--a black-and-white striped catfish found nowhere else--with little water in which to swim.
The 800 indigenous people who live along the Big Bend are among those protesting the dam. Philip Fearnside, an ecologist at the National Institute of Amazonian Research in Brazil, says, "[They] will not have the fish that they depend on and the use of the river for transportation, so it will be a real hardship for them."
In addition to Belo Monte, more than 150 other hydroelectric dams are planned for the Amazon in the next 20 years to help feed Brazil's growing need for electricity. Each dam would affect a different set of species--especially in the western Amazon, where many survive in small niches among the valleys of the Andes Mountains.
"This forest in the Andes is extremely diverse," says Clinton Jenkins, a conservation scientist at North Carolina State University.
"A dam might flood one little valley, and there are a lot of species there that don't occur anywhere else in the world."
Giant dourada catfish, for example, migrate from the lower Amazon River to the Andes to breed. Because they can't swim through dams, the population would decline. The same thing happened to migrating salmon in the northwestern United States. Dams blocked the fish from swimming upriver to spots where they would lay the next generation of eggs--one reason that some U.S. dams are now being removed (see Taking Down Darns, right).
Environmentalists warn that the negative effects of dams reach beyond their immediate location. When workers move to the construction site, they take land, building materials, and food from the rainforest. Roads built to get to the dams open up previously inaccessible parts of the rainforest. "Then loggers and illegal hunters go in and cut down the forest or overharvest the wildlife," says Jenkins. "Once you have that access, it's very hard to go back and eliminate the threat."
Ironically, the huge Belo Monte Dam could turn out to be hugely inefficient, as the Xingu's flow decreases drastically during the dry season, from June to November. "You have four months when there isn't even enough water in the river to run one of the turbines in the main powerhouse," says Fearnside.
Opponents are asking Brazil's courts to halt the construction. Proponents, on the other hand, say the risks are worth taking because Brazil needs the electricity for continued economic growth.
Even if construction stops, the numerous other dams slated for the Amazon rainforest guarantee that the debate raging there won't soon be over.
WHAT DO YOU THINK? Should the Belo Monte Dam be built to help keep Brazil's economy strong? Why or why not?
HOLDING BACK THE RIVER
The Belo Monte Dam will hold back the waters of the Xingu River. The resulting reservoir will cover an area almost the size of Chicago. The dam will divert most of that water through canals to a powerhouse, severely reducing the flow to a section of the river called the Big Bend.
THE-BELO MONTE DAM BY THE NUMBERS
Belo Monte is set to be built on the Xingu River, which is 1,979 kilometers (1,230 miles) long. 14,000 indigenous people and 9 ethnic groups will be displaced.
Belo Monte would be the world's third-largest hydroelectric dam.
THREE GORGES (CHINA): 18,000 MEGAWATTS (MW)
ITAIPU (BRAZIL): 14,000 MW
BELO MONTE: 11,000 MW
TAKING DOWN DAMS
Dams popped up across the U.S. in the early 20th century before the environmental effects were fully understood. Since 1990, about 680 dams, like these three, have been removed.
EDWARDS DAM, MAINE
The local fishing industry took a hit when the dam was built in 1837. Since the dam's removal in 1999, populations of migratory fish, including Atlantic salmon, striped bass, and endangered shortnose sturgeon, have rebounded.
GLINES CANYON DAM, WASHINGTON STATE
The 64 meter (210 foot)-high dam is the tallest U.S. dam to be dismantled. The removal, which began last September and will take three years, is expected to boost salmon and steelhead trout populations.
MARMOT DAM, OREGON
A mountain of sediment had piled up behind the dam. After the dam was dismantled in 2007, sediment could once again flow downstream and form natural fish habitats such as gravel bars.
$17 BILLION is the estimated total cost, including $800 million to lessen the environmental impact of the dam.
18 percent of the Amazon rainforest has been cleared since 1960.
That's an area twice the size of California.
The diversion of 80 percent of the Xingu River will cut off indigenous communities along a 130 km (81 mi) stretch from water, fish, and transport.
250 [km.sup.2] (97 [mi.sup.2]) is the amount of land flooded naturally during the rainy season.
500 [km.sup.2] (193 [mi.sup.2]) is the amount of land that would be flooded by the dam.
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||EARTH: RAINFORESTS|
|Date:||Aug 21, 2012|
|Previous Article:||Candid shots: rather than risk his life to get close-up photos of wildlife, a photographer sends a robot in his place.|
|Next Article:||7 minutes of terror: the most nerve-racking parts of a trip to Mars are the final moments before landing.|