El Niño: How does it affect the Amazon Rainforest?

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If you’ve been keeping up with environmental news, or even if you’ve just been confused by the weird weather over the past few months and ran some google searches, you’ve probably heard of El Niño. This global phenomenon is bringing warm weather to the typically cold northeastern US and rain to the drought-stricken west coast. Last month, we learned about seasonal changes in the Amazon, and that the rainforest is definitely not a static place! With that in mind, I started to wonder what the effects of El Niño might be on the Amazon Rainforest.

First of all, you may be wondering, what is El Niño, exactly?

Let’s back up for a second.

To understand El Niño, we need to think about how air and water moves across the globe. Warm air and water rise, while cold air and water descend. Similarly, air and water move from areas of high pressure to areas of low pressure.

These properties, along with the Earth’s rotation, drive the movement of air and water around the globe. Now, we’re familiar with the fact that weather can be difficult to predict and highly variable in the short term- we get warm days followed by cold days, and sometimes we don’t know if it’s going to rain until it starts pouring. However, over longer periods of time, there are predictable patterns that arise: summer months are warmer than winter months in temperate climates, and tropical climates get more rain during certain months.

Photo by Raechel Running, 2010

Painting by Julia Loman

Photo by Raechel Running, 2009

One pattern of air and water movement is called the Walker Circulation. This is a huge cell of movement driven by solar heat and pressure differences between the eastern and western Pacific Ocean. Warm water moves towards the western Pacific Ocean, and there is an upwelling of cool water on the Pacific coast of South America. So, when the Walker Circulation is operating normally, the eastern Pacific Ocean tends to be cool and dry, and the western Pacific tends to be warm and wet.

During El Niño, this system breaks down, for various reasons, often related to the temperature of the ocean surface. This means that the westward movement of water is weak, and cool water from the deep ocean does not rise at the coast of South America.

This is a very complex phenomenon, and scientists still don’t understand all of the causes, but the net result is that the ocean is much warmer in the eastern Pacific Ocean than usual during El Nino. And the Walker Circulation is so huge, that there are global weather consequences when it changes so dramatically. That helps explain some of the warmer-than-usual weather in North America this winter (although climate change has exacerbated these effects).

So, what is El Niño doing to the Amazon Rainforest? While it brings storms and rainfall to the west coast of North America, South America tends to experience drought during El Niño-- and this is the pattern that scientists are beginning to see for the beginning of 2016 [1]. The warm, dry weather that occurs as a result of El Niño is the perfect condition to cause forest fires all over the Amazon. This is made worse by the fact that burning is used as a tool to clear areas of rainforest for agriculture or mining: these fires can spread out of control and cause even more forest loss than would already occur.

The dry conditions have another, more subtle effect on the Amazon: rainforests simply don’t thrive as well without abundant moisture. The dryness caused by El Niño reduces growth, which means that trees store less carbon. In addition, dry weather actually causes the soil to release carbon [2]. This has serious consequences, as the Amazon is one of the most important regions of the world for taking up carbon from the atmosphere. As we burn fossil fuels, pumping carbon into the atmosphere, and warming the planet, the frequency of El Niño and other extreme weather events actually increases as well [3]. This makes the Amazon’s capacity to store carbon, taking it out of the atmosphere, even more important to the future of the planet.

While we can’t actually stop extreme weather caused by El Niño events from happening, it is clear that protecting the Amazon’s ability to store carbon is crucial. Every person has the power to help with this mission, whether it’s through making changes in your own lifestyle, or reaching out to governments and organizations that are working hard to fight climate change and rainforest loss. Plant a tree, or protect an acre of carbon-absorbing rainforest through Amazon Aid’s programs. Even the smallest actions add up to help heal the Amazon Rainforest!


[1] Vaidyanathan, Gayathri. “El Nino could ignite Amazon, drench California.” Scientific American, 2015. Web.


[2] Knight, Danielle. “Environmental Bulletin- Climate: El Nino effect on Amazon Rainforests.” Inter Press Services News Agency, 1998. Web. http://www.ipsnews.net/1998/12/environment-bulletin-climate-el-nino-effect-on-amazon-rainforests/

[3] Pratginestos, Juan. “Climate change in the Amazon.” World Wildlife Foundation, 2015. Web. http://wwf.panda.org/what_we_do/where_we_work/amazon/amazon_threats/climate_change_amazon/

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