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Deforestation of Amazon Could Alter Global Weather

By Samantha-Rae Tuthill, Staff Writer
November 23, 2013, 5:18:23 AM EST

Over the course of the past 40 years, almost 20 percent of the Amazon rainforest has been lost due to deforestation. Some experts worry that the rapid depletion of this vast ecosystem could eliminate what remains in the next 40 years. While the safety and longevity of the Amazon is important for its own sake, weather patterns and the climate can also be affected on a global scale by the increased loss of this area.

"The issue is that the Amazon is so big that it affects weather at the continental and even the global scale," Meg Symington, Amazon director at the World Wildlife Fund-U.S. (WWF), said.

According to Symington, researchers have been looking for teleconnections, the impacts such a massive forest can have beyond on just its immediate environment. The World Bank released a report in 2011, Assessment of the Risk of Amazon Dieback, which discusses how changes in the Amazon could transform it from a carbon sink to a carbon source. The density of the trees in the rainforest absorb a great deal of carbon dioxide, 0.8 to 1.1 billion metric tons of it. As the ecosystem changes, however, it could begin to release more of the greenhouse gas than it takes in, which could affect global temperatures.

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Because of the size and location of the Amazon, as well as the amount of rain that it produces, the effects it has on weather patterns reach well beyond its immediate area.

"Studies have shown that rainfall in southern South America is actually impacted by the Amazon and could decrease significantly if you have additional deforestation," Symington said. "Maybe even the American Midwest, parts of North America, in terms of the weather pattern, could be affected."

Symington said that trade winds bring 50 percent of all the rain that falls in the Amazon from evapotranspiration, which is a crucial part of the water cycle that includes water evaporated from plants; as precipitation falls in the rainforest into the lush vegetation, the evaporation of that rain from the plants creates more rain to fall. Fifteen percent of the atmosphere's water vapor comes from this process.


"All of this has to do with a tipping point," Symington said. "With deforestation, if you go beyond a certain point in the Amazon there's an issue of where the whole system becomes destabilized and you would switch from a tropical, moist forest system, to something that was much drier and more like the Cerrado of central Brazil, sort of a dry forest, savanna system. If that happened it would have a huge impact on species in the Amazon and also on the climate."

About 20 percent of the fresh river water in the world comes from the Amazon River, and drying of the forest can negatively influence that water source. Symington told that changes to this freshwater output would affect the entire current off the coast of South America, which could affect the jet stream, which would ripple into a change in weather patterns across the globe.


There is also an immediate issue of how the balance of the rain forest affects its own ecosystem.

"The Amazon is home to at least 10 percent of the world's species, probably more, because there are a lot of species that have not been discovered yet that live in the Amazon," Symington said.

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"The most fish species in the world are found in the Amazon. Too much deforestation and you lose not only the terrestrial species, but you would completely change the hydrological system in the Amazon with flooding. The river comes up meters in the rainy season and that would all change if you had this forest dieback as well."

Without the trees to absorb the river's flooding, the soil and landscape around the river would be drastically altered. In Brazil, where a large percentage of their electric energy comes from hydropower, a change to the flow of the river would affect the amount of gigawatts that the hydropower dam produces. Moderate, careful and controlled use of the Amazon also supports local food sources, livelihoods and pollinating animals and insects that agriculture depends on. Some scientists and researchers seek out genetic resources that could be used for global medicinal purposes.


Too much unnecessary change to an ecosystem can create a chain reaction on its species and on the general environment, and we may not fully know the extent of where this chain reaction may go.

"We always talk about conservation in terms of 'don't throw away the rivets,'" Syminton said. "If you pull rivet by rivet out and throw them away, the whole system falls apart, so we need to be careful. People may think, 'What's one species?' but then you never know what happens when the whole system falls apart."

The World Bank's assessment supports the same idea, stating, "Changing forest structure and behavior would have significant implications for the local, regional and global carbon and water cycles. Amazon forest dieback would be a massive event, affecting all life-forms that rely on this diverse ecosystem, including humans, and producing ramifications for the entire planet."

Have questions, comments, or a story to share? Email Samantha-Rae Tuthill at, follow her on Twitter @Accu_Sam or Google+. Follow us @breakingweather, or on Facebook and Google+.

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