The Amazon rainforest: a question of balance

October 28, 2011

Threatened by drought and uncontrolled logging, the Amazon rainforest – which plays a critical role in balancing the world's climate and sustaining vast numbers of living species – is under severe pressure.

Preparing for log extraction in Amazon
Preparing a log for extraction.
Fluting of tree butresses Tree canopy bridge in Amazon
Fluting of tree butresses is common in the Amazon. Note tree canopy bridge allowing monkeys to cross the road.
Grapple skidder in Amazon Rio Negro and Amazon rivers
Grapple skidder extracting logs. Joining of the Rio Negro (black river) and Amazon rivers. The water is black from leaching through podzol soils.

 

The Amazon rainforest is one of the three main tropical forest eco regions in the world, the other two being the Congo Basin rainforest and the South East Asian rainforest. The Amazon rainforest is a moist, broadleaf forest that covers most of the Amazon Basin of South America. This basin encompasses seven million square kilometres (1.7 billion acres), of which five and a half million square kilometres (1.4 billion acres) are covered by the rainforest.

The region includes territory belonging to nine countries. The largest part of the rainforest is in Brazil, with 60% of the rainforest area, followed by Peru with 13%, and minor amounts in Colombia, Venezuela, Ecuador, Bolivia, Guyana, Suriname and French Guiana.

The Amazon represents over half of the planet's remaining rainforests, and it comprises the largest and most species-rich tract of tropical rainforest in the world.

Biodiversity
Wet, tropical forests are the most species-rich biome, and tropical forests in the Americas are consistently more species rich than the tropical forests of Africa and Asia. One in ten known species in the world live in the Amazon rainforest.

This constitutes the largest collection of living plants and animal species in the world – it is home to an estimated 40 000 plant species of which 11 000 are tree species (as opposed to 9 000 species in the Cape floral Kingdom). To date, at least 3 000 fish species, 1 294 birds, 427 mammals, 428 amphibians, and 378 reptiles have been scientifically classified in the region.

One in five of all the birds in the world live in the rainforests of the Amazon. The rainforest contains several predatory species. Among the largest predatory creatures are the Black Caiman, jaguar, cougar, and Anaconda snake. In the rivers, electric eels can produce an electric shock that can stun or kill, while piranha are known to injure humans. Various species of poison dart frogs secrete toxins through their flesh.

Harvesting
Although commercial harvesting of the Amazon remains controversial, responsible concessionaires are managing their concessions in a sustainable way, many of them FSCTM certified. There are only a few select tree species that are harvested commercially. Of these, four to eight trees are removed per ha on a 25-year cycle. Felling is done by chainsaw and extraction by skidders and/or tracked dozers.

Deforestation
Between 1991 and 2000, the total forest area lost in the Amazon increased from 415 000 to 587 000 square kilometres, an annual deforestation rate of 0.4%. Most of the lost forest is due to agriculture. Except for livestock pasture, Brazil is currently the second-largest global producer of soybeans after the United States. The needs of soy farmers have been used to justify many of the controversial infrastructure projects that are currently developing in the Amazon. Two new highways successfully opened up the rain forest and led to increased settlement and deforestation. The mean annual deforestation rate from 2000 to 2005: 22,392 km2 was 18% higher than in the previous five years. However, deforestation has declined in the Brazilian Amazon in recent years.
Climate change

One square kilometre of Amazon rainforest can contain about 90 790 metric tonnes of living plants (907,9 tonnes/ha). The average plant biomass is estimated at 356 tonnes per ha. There is a concern about loss of biodiversity that will result from destruction of the forest, and also about the release of the carbon contained within the vegetation, which could accelerate global warming. Amazonian evergreen forests account for about 10% of the world's terrestrial primary productivity and 10% of the carbon stores in ecosystems.

By way of comparison, deforestation in the world is contributing to 17% of the global Green House Gas emission, equivalent to the emission by the transport sector. Deforestation of one hectare of tropical rainforest releases about 800 t CO2, equivalent to the average annual emission of 200 private cars!

In 2005/2006, parts of the Amazon basin experienced the worst drought in the last hundred years. In 2010, the Amazon rainforest experienced another severe drought, in some ways more extreme than the 2005/2006 drought. Approximately 3 million km2 of rainforest was affected, as opposed to 1.9 million km2 in 2005. In a typical year, the Amazon absorbs 1.5 gigatons of CO2; during the 2005 drought, five gigatons were released instead and in 2010, eight gigatons of CO2 were released. It has been reported that the forest in its present form could survive only three years of drought. Some Brazilian scientists argue that this drought response, linked with the effects of deforestation on regional climate, is pushing the rainforest towards a 'tipping point' where it would irreversibly start to die. It concludes that the forest is on the brink of being turned into savanna or desert, with catastrophic consequences for the world's climate. However, this has not been well substantiated at all to date.

As indigenous territories continue to be destroyed by deforestation, indigenous peoples' rainforest communities continue to disappear, while others struggle for their cultural survival and the fate of their forested territories.

Published in August 2011

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