Amazon river at record low levels; deforestation blamed
mongabay.com
September 30, 2005
The Amazon River in Peru is at its lowest level in 30 years of record keeping according to a report in Peruvian daily newspaper El Comercio. Local officials say deforestation is the likely culprit of the low water levels.
While variable water levels are characteristic of the Amazon river ecosystem, the increasingly extreme fluctuations are of great concern. Low water levels are wreaking havoc on the shipping industry in the region. In Iquitos, a city in the heart of the Peruvian Amazon which is only accessisble by plane or boat, ships and barges are having difficulty navigating the river, resulting in serious shipping delays. Currently, the 600 km Iquitos-Pucallpa route on the Amazon and Ucayali river takes around 25 days for a 500-barrel barge, instead of the usual 4 to 6 during normal low water conditions. At the confluence of the Itaya and the Amazon, downstream from Iquitos, river depths have fallen from the normal 49 feet (15 meters) to as shallow as 3 feet (80 cm) in places. Recently, low river levels prevented a Peruvian cargo liner which operates between Houston, Texas and Iquitos from even making it into Peruvian waters. The vessel had to drop anchors 1000 km downstream in Brazil and its cargo transfered to smaller barges.
Local officials are blaming deforestation of the upper reaches of the Amazon in the Andes for the fall in river levels. Forest clearing impacts rainfall by disrupting the local water cycle. Under normal conditions, forests add to local humidity through transpiration — the process by which plants release water through their leaves. Moisture is transpired and evaporated into the atmosphere where it contributes to the formation of rain clouds. Scientists estimate that 50-80% of the moisture in the central and western Amazon remains in the ecosystem water cycle. However, when forests are cut, as is the case in Peru, less moisture is evapotranspired into the atmosphere, resulting in the formation of fewer rainclouds and less rainfall.
Officials fear that low water problems will only worsen in coming years as more forest is cleared and glaciers in the Andes continue to retreat. Glaciers, which are the source for as much as 50% of the water in the upper Amazon, are fast disappearing in Peru. According to a 1997 study by the Peruvian government, the country’s glaciers have shrunk by more than 20% in the past 30 years. Further, the National Commission on Climate Change in Lima projects that Peru will lose all its glaciers below 18,000 feet in elevation in the next decade and possibly all its glaciers within the next 40 years. The impact on the Amazon, when combined with deforestation, could be devestating to the region’s climate, water cycle and economy.
October 1 update from The Guardian
The following is excerpted from “Amazon dries out as worst ever drought hits rainforest” by Alex Bellos in Manaus, Saturday October 1, 2005
-
Large parts of the Amazon rainforest are at their driest in living memory, a direct consequence, scientists say, of the severe hurricane season off the US Gulf coast…
“There is no rain here because the air is descending, which prevents the formation of clouds,” said Ricardo Dellarosa, of the Amazon Protection Organisation (Sipam) in Manaus. “The air is descending here because the air is rising very intensely in the north Atlantic, creating storms and hurricanes. What goes up must come down.”
Gilvan Sampaio of the National Institute of Space Research said the north Atlantic was slightly warmer than usual, which had shifted the tropical weather system further north. A secondary factor, he added, was that cold fronts that usually came from the south of Brazil at this time of year had not been arriving. “These cold fronts have been heading straight into the ocean, instead of heading north towards the Amazon.”
Even though the river levels in the south-western Brazilian Amazon are always low at this time of year, the scale is much worse than usual and has hit areas never previously affected.
“It’s the worst it’s been in 60 years,” said Elpidio Gomes da Silva Filho, head of the Administration of West Amazon Waterways.
BACKGROUND
The Amazon River
The Amazon River is the most voluminous river on Earth, eleven times the volume of the Mississippi, and drains an area equivalent in size to the United States. During the high water season, the river’s mouth may be 300 miles wide and up to 500 billion cubic feet per day (5,787,037 cubic feet/sec) flow into the Atlantic. For reference, the Amazon’s daily freshwater discharge into the Atlantic is enough to supply New York City’s freshwater needs for nine years. The force of the current, from sheer water volume alone and virtually no gradient, causes the current to continue flowing 125 miles out to sea before mixing with Atlantic salt water.
The Amazon is also one of the most biodiverse regions on the planet, housing up to 30% of the world’s species. The Amazon river alone is home to some 3000 species of fish.
The History of the Amazon
 Satellite Photo of the Amazon – Courtesy of INPE |
Scientists believe the Amazon River once flowed westward, perhaps as part of a proto-Congo (Zaire) river system from the interior of present day Africa when the continents were joined as part of Gondwana. Around fifteen million years ago, the collision of the South American plate with the Nazca plate created the Andes mountain range and blocked the flow of the Amazon, causing the river to become a vast inland sea. Gradually this inland sea became a massive swampy, freshwater lake and the marine inhabitants adapted to life in freshwater. For example, over 20 species of stingray, most closely related to those found in the Pacific Ocean, can be found today in the freshwaters of the Amazon.
About ten million years ago, waters worked through the sandstone to the west and the Amazon began to flow eastward. At this time the Amazon rainforest was born. During the Ice Age, sea levels dropped and the great Amazon lake rapidly drained and became a river. Three million years later, the ocean level receded enough to expose the Central American isthmus and allow mass migration of mammal species between the Americas.
This article used information from El Comercio via the LatinReporters.com web site.