Satellite image of the Turucui dam and associated deforestation in Brazil. (Photo courtesy of DigitalEarth)
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THREATS TO TROPICAL RIVERS AND LAKES
Tropical rainforest waters are highly threatened today by hydroelectric projects, erosion from deforestation, overfishing,
and poisoning from oil and chemical spills. The effects from the degradation of these waters are widespread, inflicting
damage on the global economy, the environment, and local peoples.
Damming the Amazon
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Balbina dam outside Manaus, Brazil
The Balbina dam flooded some 2,400 square kilometers (920 square miles) of rainforest when it was completed. Phillip Fearnside, a leading expert on the Amazon, calculated that in the first three years of its existence, the Balbina Reservoir emitted 23,750,000 tons of carbon dioxide and 140,000 tons of methane, both potent greenhouse gases which contribute to global climate change.
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Increasing demands for energy are putting the world's rivers at risk.
Hydroelectric projects are responsible for flooding vast areas of rainforest. The decay of forest wood adds more
greenhouse gases to the atmosphere contributing to global warming. This flooding means that terrestrial species,
including humans, must migrate to new areas usually leading to more deforestation. Fish species adapted to the
riverine environment must adapt to lake conditions or perish. Dams disrupt the migration of species which move
up- or downriver to spawn.
Erosion is a well-known result of deforestation with serious consequences for river commerce and river life. Sediments
build up creating sandbars and shallows and interfering with river transportation. Similarly, sediment build-up reduces
the effectiveness of existing hydroelectric projects. Erosion and the resulting decline in water clarity causes
downstream mayhem for offshore coral reefs. River inhabitants also suffer due to the reduced water clarity. Species
that rely primarily on sight decline the most, while the increased amount of suspended particles interferes with
fish gills. Erosion inhibits plant growth and hinders the development of fish eggs.
Overfishing is a problem that plagues the world's oceans (35-60 percent are overfished worldwide [overfishing news]) and freshwater habitats.
Regional declines in catch have been reported throughout the Amazon. The loss of certain species responsible for
seed dispersal will have a negative effect on the renewal of the rainforest.
Poisoning from spills and pollution from industrial processes mining, and sewage continue to reduce the diversity
of rainforest waters, in addition to affecting human populations. The much publicized spill on the Essequibo river,
along with the continued spilling of oil in Peru and Ecuador, has had an impact of river life.
Article
on the effects of mercury in aquatic habitats (mercury pollution in the Amazon frequently results from mining activities).
Review questions:
- How are rainforest rivers under threat?
- How do dams contribute to global warming?
- Why are dams usually bad for native fish species?
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Continued: People of the rainforest
This article was written by Rhett A. Butler [bibliographic citation for this page] and was last updated on the most recent date listed in the column on the right side.
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WEEKLY NEWSLETTER
INTERACT
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Recent news
Environmental news - month in review: setbacks for the palm oil industry, climate outlook darkens
(02/02/2012) Here mongabay.com provides a quick review of forest-related news for January 2012.
Brazilian mining company connected to Belo Monte dam voted worst corporation
(01/31/2012) The world's second largest mining company, Vale, has been given the dubious honor of being voted the world's most awful corporation in terms of human rights abuses and environmental destruction by the Public Eye Awards. Vale received over 25,000 votes online, likely prompted in part by its stake in the hugely controversial Brazilian mega-dam, Belo Monte, which is being constructed on the Xingu River. An expert panel gave a second award to British bank Barclay's for speculation on food prices, which the experts stated was worsening hunger worldwide.
Brazil begins preliminary damming of Xingu River as protests continue
(01/19/2012) Damming of the Xingu River has begun in Brazil to make way for the eventual construction of the hugely controversial, Belo Monte dam. The Norte Energia (NESA) consortium has begun building coffer dams across the Xingu, which will dry out parts of the river before permanent damming, reports the NGO International Rivers. Indigenous tribes, who have long opposed the dam plans on their ancestral river, conducted a peaceful protest that interrupted construction for a couple hours.
Deforestation, climate change threaten the ecological resilience of the Amazon rainforest
(01/19/2012) The combination of deforestation, forest degradation, and the effects of climate change are weakening the resilience of the Amazon rainforest ecosystem, potentially leading to loss of carbon storage and changes in rainfall patterns and river discharge, finds a comprehensive review published in the journal Nature.
Top 10 Environmental Stories of 2011
(12/22/2011) Many of 2011's most dramatic stories on environmental issues came from people taking to the streets. With governments and corporations slow to tackle massive environmental problems, people have begun to assert themselves. Victories were seen on four continents: in Bolivia a draconian response to protestors embarrassed the government, causing them to drop plans to build a road through Tipnis, an indigenous Amazonian reserve; in Myanmar, a nation not known for bowing to public demands, large protests pushed the government to cancel a massive Chinese hydroelectric project; in Borneo a three-year struggle to stop the construction of a coal plant on the coast of the Coral Triangle ended in victory for activists; in Britain plans to privatize forests created such a public outcry that the government not only pulled back but also apologized; and in the U.S. civil disobedience and massive marches pressured the Obama Administration to delay a decision on the controversial Keystone XL pipeline, which would bring tar sands from Canada to a global market.
More rainforest news
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