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Mario Osava* - IPS/IFEJ
RIO DE JANEIRO, Apr 10 2007 (IPS) - An Amazon region that is less lush, where forest is replaced by grasslands, is the image drawn by the latest scientific reports in which meteorologists are taking the lead, going beyond even the direst warning of ecologists.
This process could "convert into savannah" as much as 60 percent of the Amazon region, says a 2003 study by Carlos Nobre and Marcos Oyama, of Brazil's National Institute of Space Research (INPE).
Global warming "will greatly amplify" those effects, says the IPCC in the second volume of its 2007 report, "Impacts, Adaptation and Vulnerability", released Apr. 6 in Brussels.
The IPCC report, of which Nobre was one of the contributing authors, emphasises the urgency of containing the deforestation of the Amazon, a process that is responsible for 75 percent of Brazil's climate-changing greenhouse gas emissions.
"Brazil can only win with this," because it would protect enormous future wealth and would give Brazil a leadership role in the climate change debate, said Antonio Ocular Manzi in an interview. He is the executive manager of the Large-Scale Biosphere-Atmosphere Experiment in the Amazon, a research initiative involving Brazilian and foreign scientists.
In some areas, the average temperature could increase as much as 12 degrees, said Philip Fearnside, a U.S. ecologist and Amazon expert who for the last 30 years has been working with Brazil's National Institute for Amazonian Research, INPA. This will happen if nothing is done to contain deforestation or global climate change, he added.
Warmer temperatures mean that trees consume more water to carry out photosynthesis, which is why it has such a big effect on forests. But climate change's great threat to the Amazon is that it could generate a permanent El Niño phenomenon (a now cyclical warming of surface waters in the Pacific Ocean), manifested in more heat and longer periods of scant rains north of the Amazon River, says Fearnside, also a contributor of the IPCC report.
That was the case in 1997-1998, when drought triggered devastating fires in the northern Brazilian state of Roraima. And in 2006, a moderate El Niño greatly curbed rainfall along the Rio Negro, a main tributary of the Amazon River.
Global warming so far – moderate compared to what scientists say is expected to come – has been accompanied by an increased frequency of El Niño since 1976.
El Niño will be "more frequent and more intense" if humans don't take action to mitigate the greenhouse effect, Fearnside said in an interview for this article.
To the south of the Amazon River drought is also a problem, related to the warming of waters in the Atlantic Ocean. In 2005 there were uncontrollable fires in Acre state, which is carrying out a much-lauded forest conservation policy. Fires are the big factor in the conversion of forests into savannah.
Another reason for being "on the verge of the 'savannisation' of the Amazon" is the existence of parts prone to that process, like Santarém, in the region's east, with tropical forests but rainfall equivalent to that of Brasilia, which is located in the country's Cerrado, a savannah biome, Fearnside explained.
An isolated voice has spoken out against such dire predictions. Respected Brazilian geographer, Aziz Ab'Saber, 83, says that just the opposite will occur: there will be a greater density of forests in the Amazon and other biomes as a result of global warming.
The heat will increase evaporation of waters from the Atlantic and this humidity will reach the South American continent, increasing rainfall, Ab'Saber has said in many interviews given since the publication of the first volume of the IPCC report in February.
The expert, who applied the "refuge theory" to explain the formation of the Amazon forests, points out that 6,000 years ago the planet went through a "climatic optimum", with a warming phase that raised ocean levels after the ice age and caused more rains and the "re-tropicalisation" of Brazil.
The warm currents of the Atlantic will continue, and they were not taken into consideration by the IPCC, says Ab'Saber.
Other researchers avoid controversy, but note that the current scientific studies are based on complex mathematical models that include a wide array of variables, such as past experience and ocean currents.
"The results are consistent" and perhaps provide a better assessment of the water cycle, with more recent data and which Ab'Saber hasn't taken into account, said INPE researcher Gilvan Sampaio.
About half of the Amazon region's rainfall is the product of re-evaporation from the forests themselves. Deforestation reduces the amount of water vapour, and the effects would also be felt in central-southern Brazil and parts of Argentina, Bolivia and Paraguay, said Sampaio.
"At least 30 percent of the rains in southeast Brazil come from the Amazon," where humid winds move from the east that the Andes Mountains push southward, he explained.
But the question of Amazon rainfall still poses uncertainties, said Manzi. Most of the assessments also indicate more rains in the western Amazon, near the Andes, and therefore denser forests.
Meanwhile, in the eastern Amazon there are doubts about predictions for scant rains. In general, the mathematical models point to "drier climate than the reality", but they correctly predict the evolution, he acknowledged.
We can't rule out less tragic effects than the ones predicted, but it depends on whether measures are taken immediately, such as a dramatic reduction in Amazon deforestation, Manzi added.
Since the 1970s, extreme climate phenomena have intensified, like the 2005 drought in the south-west Amazon.
Fearnside underscored the synergy between droughts triggered by El Niño and the warming of the Atlantic, destruction of forests from logging and the expansion of agriculture, and fires caused by human activity and drought, which tend to claim the biggest trees, vital for maintaining the forest microclimate.
(*This story is part of a series of features on sustainable development by IPS-Inter Press Service and IFEJ – International Federation of Environmental Journalists.)
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