Friday, November 14, 2008
The Amazon: ICU Patient or Environmental Casualty?
It is difficult not to think of the Amazon in human physiological terms. The Amazon rainforest, the largest in the world by far (if it were a country it would be the ninth largest in the world) is often called the lungs of the world, the world's respiratory system. And the Amazon River is the rainforest's circulatory system, if not the key to the circulatory system of the entire world. The Amazon releases one fifth of all the river discharge into the world's oceans (up to 300,000 m³ per second in the rainy season), a discharge greater than the next 8-10 largest rivers in the world combined. The Amazon is also arguably the world's longest river, a claim that is, to many experts, negated by the Nile River. Both are, nonetheless, well over 4000 miles in length.
But the Amazon, like most of the world's other major rivers, may soon have to be put on life support!
Most of the Amazon river's rapidly increasing problems are due to the intensive, government-encouraged and government-supported deforestation of the Amazon rainforest. Each year an area up to the size of Texas is denuded of its old-growth forest cover. The Amazon rainforest has become an involuntary heavy smoker and the lungs of the planet are struggling. The trees cut down in the deforestation effort are not converted to lumber to satisfy the world's increasingly desperate need for that commodity. They are burned in the field, the massive smoke plumes clearly visible from space.
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Deforestation of the Amazon River basin has followed a pattern
of cutting, burning, farming, and grazing.
Most of the deforested land in Amazonia is converted to pasture for cattle for Brazil's still-expanding beef industry. A lot of it, however, is used to grow high-income corn, soy and sugar cane, most destined for the skyrocketing biofuel industry (Brazil has become a world leader in biofuel production and usage). Much of the deforestation is carried out, often illegally, by indigenous, subsistence farmers escaping the ghettos surrounding Rio de Janiero, Sao Paolo and other major Brazilian cities.
But all of these efforts run into the same problem: the poor quality of the Amazon rainforest soil. The heart of the Amazon rainforest is in the forest canopy. The soil on the forest floor serves little purpose beyond holding the roots of trees. Even the incredibly complex and vibrant animal life of Amazonia (more than one third of all species in the world live in the Amazon rainforest) is predominantly made up of canopy dwellers, dwarfing the number of ground-dwelling species.
When the forest is cleared and the canopy opened up that nutrient-poor soil on the forest floor is exposed to the relentless onslaught of the tropical sun (the mouth of the Amazon is on the equator). The sun dries it up and it becomes an impermeable surface hardpan that plants can't penetrate with their roots. When the rainy season comes the dried, weak, unconsolidated soil is washed away by the torrential rains. The nutrient-poor and biologically-deprived soil does not hold water, most of which runs off into the nearest river, all of which lead to the Amazon.
Silting up the Amazon
Despite its massive water volume and the high volume of silt the Amazon river carries, at it's mouth the Amazon is not even in the top five of the world's rivers in terms of silt by volume of water. And that is a very telling symptom of the Amazon's present and growing problem. Over the course of its travels to the Atlantic Ocean the Amazon may carry as much or more silt than any other river on the planet. But a very large volume of that silt never makes it to the sea.
The lower reaches of the Amazon are navigable up to Iquitos, Peru, 2300 miles from the Atlantic. In that 2300 miles the Amazon drops only 106 meters (348 feet), an extremely gradual rise. In that 2300 miles the Amazon meanders and twists and turns through a wide flood plain which, during the rainy season, can see the river swell to over thirty miles in width. The river itself is widening by up to several meters per year. This is, in part, being caused by the breakdown of the soft river banks by the wakes from boats and ships able to navigate the river up to Iquitos.
The constant twisting and turning, the gradual gradient and the tremendous length of the river all combine to cause the majority of the silt the river carries to be deposited during its journey, rather than carrying it to the sea. The upper reaches of the Amazon have some of the best and most extensive river beaches in the world. This in-transit deposition of silt is why, despite its massive volume, the Amazon does not have a delta at it's mouth. Most of the silt that would build up into a delta has been deposited further up river. It has at its mouth, however, created over geological time the largest river island in the world, Marajo Island, which is roughly the size of Switzerland.
The problem worsens
This depositing of such massive amounts of silt along the whole 2300-mile length of the lower Amazon means that, over time, much of the river will eventually silt up from the increased run-off from deforested rainforest. The river become unnavigable except during the rainy season. Many of the over 1100 tributaries could eventually be blocked by silt build-up, all of which could eventually reduce the volume in the Amazon. The greater the silt build-up the more the Amazon will spread out during the rainy season, possibly destroying large tracts of forest not evolved to surviving much of the year in flood conditions. Already many tributaries of the Amazon are, for the first time in memory, drying up during the dry season because of silt build-up.
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Amazon dries up
As well as silt, the Amazon carries significant volumes of toxins from mining operations on its upper reaches and of untreated sewage from the numerous growing communities along its bank (Iquitos has a population of over 370,000). These toxins, like the silt, settle out long before the Amazon reaches the sea, causing a toxic build-up in the river bottom and in the soil along the shores of the river. These toxins are having an increasing impact on the freshwater species in the river and its tributaries and on the land species that live along its shores.
The changes being inflicted by man on the Amazon river and rainforest are having an increasingly serious impact on the global biosphere. The rainforest is one of the major carbon sinks of the world and their destruction is; speeding the onset and severity of global warming; impeding the planetary hydro cycle and contributing to changing global weather patterns; decreasing the nutrient density of the Atlantic Ocean (the Amazon distributes nutrients hundreds of miles out to sea at its mouth) seriously affecting the survivability of ocean species in the Atlantic Ocean.
Physician, Heal Thyself
The Brazilians, of course, are doing nothing different with their rainforest than Europeans, North Americans, Africans, Australians and Asians haven't already done with their forests. What right, they can and do argue, does the rest of the world have to expect them to forego the benefits they arguably receive from its destruction? It is not unlike asking China to curtail its CO2 emissions, at serious economic cost, because of their impact on the global atmosphere.
Brazil's problem - And China's and Africa's - is a global problem. The cost of remedying it must be global as well. If we cannot establish a global outlook on environmental issues we are never going to stop the destruction of the global biosphere, because all such destruction is essentially local. For Brazil to halt its destruction of the Amazon rainforest has a global benefit but, at the moment, a strictly Brazilian cost. That is a basic disconnect.