Amazon Rainforest Is Browning and Dying

First Posted: Oct 22, 2013 10:01 AM EDT

The southern part of the Amazon rain forest is browning and dying and an extension of 3 weeks has been observed in the dry season of the forest, unlike 30 years ago. Climate change is believed to be the reason behind this adverse impact on the forest, according to a study.

A team of researchers led by Prof. Rong Fu, a climate scientist at the University of Texas at Austin's Jackson School of Geosciences, studied the ground based rainfall measurements of the past three decades and observed that the dry season in southern Amazon got elongated by a week every decade, since 1979.

On the other hand, reduction in the levels of floods caused by rainy season was observed. This change is increasing the risk of bushfires as well as forest dieback. These results were reported by the IPCC (Intergovernmental Panel on Climate Change) on the basis of climate models.

"The length of the dry season in the southern Amazon is the most important climate condition controlling the rain forest," Prof. Fu said in a statement. "If the dry season is too long, the rain forest will not survive."

These alterations taking place in the climate can also raise production of greenhouse gases in the environment and disturb the life cycle and damage the ecosystem of  the world's richest biodiversity, the Amazon, severely.

The wildfires are an outcome of the elongated dry season and reduced rainfall. The depletion in the rainfall doesn't allow enough water to be stored in the soil and ground, which the trees use to survive the dry season and the stretched dry season strains the trees of the rainforest even more, making them more vulnerable to forest fires.

The extended dry season is a result of manmade greenhouse effect.

"Most likely explanation for the lengthening dry season in the southern Amazon in recent decades is human-caused greenhouse warming, which inhibits rainfall in two ways. First, it makes it harder for warm, dry air near the surface to rise and freely mix with cool, moist air above," the researchers explained. "Second, it blocks cold front incursions from outside the tropics that could trigger rainfall."

The climate models represented by the IPCC apparently did a poor job according to Prof. Fu, as they portrayed the Amazonian dry season as only slightly elongated.

In 2005, a severe drought was seen in the Amazon and about 1 pentagram of carbon dioxide was released into the atmosphere, which is equivalent to about one-tenth of yearly human emissions. The researchers predict that this might become the new standard for carbon dioxide emission rates for the forest for this century if the spell of the dry weather prevails over the Amazon for a longer time.

 "Because of the potential impact on the global carbon cycle, we need to better understand the changes of the dry season over southern Amazonia," says Fu.

Various scientists blame human activities like deforestation for the severe climatic alterations. These scientists warn that the rainforest might also transform in to a savanna.

Some previously conducted studies also held deforestation as the cause of depletion in the rainfall, but the extended dry season was never considered.

But it was observed that more deforestation took place in south eastern Amazon, but the impact of the longer dry season was more prominent on south western Amazon. This happened because northwestern Amazon has much higher rainfall and a shorter dry season compared to the southern Amazon. Fu and her fellow researchers believe it is much less susceptible to climate change.

See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone

©2017 All rights reserved. Do not reproduce without permission. The window to the world of science news.

Join the Conversation

Real Time Analytics