Forget oxygen — the Amazon’s destruction could threaten rain and food growing: experts
The wildfires ravaging the Amazon have focused new attention on the ongoing destruction of this tropical rainforest — and prominent voices have amplified factors that do not stand up to critical scrutiny.
As wildfires have grown, the Amazon rainforest has been called the “lungs of the planet,” a place that produces 20 per cent of Earth’s oxygen.
The net production of oxygen by forests — and all land plants — is “very close to zero,” Scott Denning, professor of atmospheric science at Colorado State University, wrote in The Conversation.
However, even if that fact doesn’t stand up to scrutiny, the Amazon rainforest is facing very serious environmental threats that resonate far beyond South America.
WATCH (Aug. 27, 2019): Amazon fires continue to burn as Bolsonaro rages against Macron
One of those threats is rainfall, or the lack thereof, that could result from deforestation, Kai Chan, a professor at UBC’s Institute for Oceans and Fisheries, told Global News.
Chan described the Amazon as a “massive rain factory,” where most of the water that is evaporated from the Amazon falls right back on top of it.
“There’s a current of air in the atmosphere, basically, and it dumps water and then picks it up and travels further, picks it up, and that happens about eight times before the Amazon finishes in this current,” he explained.
In numerous parts of the world, rain falls from atmospheric rivers, or “rivers in the sky,” phenomena that carry an amount of water vapour equivalent to the flow at the mouth of the Mississippi River, which falls as rain or snow.
The atmospheric river that floats over the Amazon rainforest is more like a lake, feeding the region in a cycle, Chan said.
That system helps to feed a region that is home to 10 per cent of all of the world’s known wildlife species — and there may be plenty more that haven’t yet been discovered.
On a day when the sun is shining, as much as 20 billion tonnes of water evaporates off the Amazon rainforest’s trees into the sky, Antonio Donato Nobre, a researcher at the National Institute of Amazonian Research, said in a 2015 TED Talk.
That’s more water than the Amazon River pours into the Atlantic Ocean in one day.
WATCH (Aug. 26, 2019): Brazilian indigenous chief calls on world leaders to save Amazon
This cycle, however, is under threat from deforestation, which is happening at an accelerated rate in the Amazon.
Deforestation grew in the rainforest by 90 per cent in June and by 280 per cent in July, according to Brazil’s National Institute for Space Research, as quoted by the LA Times.
As many as 76,000 fires are also burning in the Amazon, representing an increase of more than 80 per cent from the same time frame in 2018, reported National Geographic.
“The big concern is that once you lose enough of the Amazon, you break that lake and you stop having enough rainfall that can sustain the forest, such that it will continue to evaporate,” Chan said.
Deforestation was directly linked to rainfall patterns around the world in a 2005 study out of Duke University, NASA’s Goddard Space Flight Center explained.
That study looked at tropical forests in the Amazon, Southeast Asia and Central Africa, and found that if deforestation were to happen on a mass scale, then rainfall patterns would be disrupted, leading to declines in certain areas and increases in others.
WATCH (Aug. 26, 2019): Drone footage shows extent of damage to portion of Amazon rainforest after wildfires
Destruction of the Amazon rainforest, for instance, could dramatically reduce rainfall in northern Mexico, Texas and the Gulf of Mexico in spring and summer, a time when water is needed for farming.
Deforestation could particularly affect production of major crops like sugarcane and soybean, Chan said.
Complete deforestation in all three of the studied regions could redistribute rainfall, reducing it in California during winter, and increasing it in the southern Arabian Peninsula.
The study found that the Amazon Basin “literally drives weather systems around the world,” the flight centre said.
“The tropics receive two-thirds of the world’s rainfall, and when it rains, water changes from liquid to vapour and back again, storing and releasing heat energy in the process.
“With so much rainfall, an incredible amount of heat is released into the atmosphere — making the tropics Earth’s primary source of heat redistribution.”
That wasn’t the only study to raise alarm about the effects of deforestation in the Amazon.
A 2018 working paper produced by the World Resources Institute found that continental-scale deforestation in the Amazon, Central Africa or Southeast Asia would result in a warmer and drier climate in those regions.
Complete deforestation, it said, could see the climate warm by as much as 2 C in those regions and rainfall decline by 15 per cent.
The destruction of the Amazon rainforest may not be far off either, given the rate at which deforestation is taking place.
If anywhere between 20 and 25 per cent of the rainforest were lost, then the whole area would turn to a “savannah-like state,” Chan told Global News.
That assertion is backed up by Carlos Nobre, a professor at the University of Sao Paulo.
He has conducted research showing this threshold at precisely the level that Chan mentioned.
And the Amazon rainforest has already lost as much as 17 per cent of its trees, Nobre told the LA Times.
“We are almost seeing the tipping point before us.”
The Brazilian government, facing international backlash over how it has handled the wildfires, has banned most legal fires used in land clearing for 60 days.
The government has also accepted planes from Chile to fight the fires.
This, after President Jair Bolsonaro rejected US$20 million in funding to help fight the fires, and after he took exception to Macron’s remarks on the blazes.
For Chan, the fires are “just one example of the kinds of interconnected global problems that we really need to deal with better.”
— With files from the Associated Press
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