Smoke rises from a processing mill at a palm oil plantation in Sumatra, Indonesia

The world's tropical forests can help us limit climate change — if we let them

Tropical forests are a treasure trove of biodiversity and contain vast stores of carbon that, if released through deforestation, threaten the stability of Earth’s climate system.

Living on Earth

Smoke rises from a processing mill at a palm oil plantation in Sumatra, Indonesia, Saturday, Sept. 8, 2018. The punishing effects of palm oil on the environment have been decried for years.

AP
 

At least 130 countries have committed to halting and reversing forest loss and land degradation by the year 2030. 

Preserving forests, particularly old growth tropical forests, is essential to limiting climate damage because they hold a vast amount of carbon in them, says Max Holmes, acting president and executive director of the Woodwell Climate Research Center in Falmouth, Massachusetts.

“The concern is that if the trees are cut down, if they burn, if human activities otherwise get rid of [them], the carbon that's been locked up in the trees for decades — and centuries, in many cases — goes into the atmosphere and leads to more warming,” Holmes explains.

A few numbers help put this into context, Holmes says: First, there are currently about 850 billion tons of carbon in the atmosphere. All the forests on Earth contain about 500 billion tons of carbon — in their vegetation and in the root systems below ground. The tropical forests of the world contain about 300 billion tons of carbon, which means that roughly 60% of global forest carbon is in tropical forests.

“So, you can see how losing carbon from tropical forests can have a big impact on how much carbon is in the atmosphere and thus how much the Earth warms,” Holmes says.

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Human activities put between 11 and 11.5 billion tons of carbon per year into the atmosphere. Ten billion tons come from fossil fuels — oil, gas and coal production and consumption — and about 1 to 1.5 billion tons from deforestation and land-use change.

So, over the last 30 years, since the United Nations first began talking about the need for agreements to limit climate change, humanity has put about 300 billion tons of carbon into the atmosphere.

"It's getting a lot more difficult and a lot more expensive to reverse course [on climate change] now."

Max Holmes, acting president and executive director, Woodwell Climate Research Center

“That just means that we have to work a lot harder now. It's getting a lot more difficult and a lot more expensive to reverse course now,” Holmes says. “But that also just makes it a lot more urgent that we get to work on this right away.”

Of the carbon that humanity activities put into the atmosphere, only about half of it stays there, Holmes notes. The ocean and the land suck the other half out of the atmosphere and store it. “So, they're both doing us a big favor, helping to pull some of that carbon that we put into the atmosphere back out,” he says.

The Amazon is the world’s largest tropical forest. The second largest is in Africa, in the Congo. The forests of Indonesia are not as large, but they are very carbon rich, Holmes says — and they are all under threat.

Rapid change is underway in the Amazon right now, which must be reversed, Holmes warns. The Congo is more pristine because it has had less direct human intervention. In Indonesia, palm oil plantations are the biggest driver of deforestation: Forests are cleared to plant palm trees to create palm oil. A lot of these forests are on peatlands, which are carbon rich areas. So, when these forests are cleared, it’s sort of a “double whammy," Holmes says.

“Not only are you losing the carbon that's in the trees, but there's a lot of carbon locked up in those peatlands soils in some of those areas,” he explains. “Once the soils dry out, that carbon that's been locked up in the peat for a long time can also be released to the atmosphere."

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Holmes warns that there is a big difference between carbon stored in old growth tropical forests and the carbon-storing potential of young, regrowing or re-planted forests.

“Sometimes it's argued that you can cut down trees and the forests are going to regrow, this is a renewable resource,” he says. “On the one hand, that's certainly true. The issue is the timeframe.”

Holmes likes to use the analogy of a bank account to explain this. If you start a savings account when you’re young, it will grow every year and accumulate money. But it takes a long time to build up a large balance. And you can blow it in a hurry if you go out and spend it all on a new car or something else. The balance can quickly go down to zero.

The same is true for forests and carbon. It takes forests a long time to build up the vast amounts of carbon they store.

"Just like you can empty out your bank account in a hurry, you can empty the carbon out of a forest in a hurry."

Max Holmes, acting president and executive director, Woodwell Climate Research Center

“It's not a year, it's not 10 years, it's in many cases not even 100 years. … Just like you can empty out your bank account in a hurry, you can empty the carbon out of a forest in a hurry. You chop those trees down, you burn them, all that carbon goes back to the atmosphere right away. Yeah, you can build it back, but it takes a lot of time.”

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Climate change is accelerating and its effects are getting worse every year, so “we don't have that time,” Holmes insists. “We've got to keep the carbon in the forests that are standing. Where we can restore forests, we need to start doing it; it will pull carbon out of the atmosphere, but it will take them a long time to restock that balance they had started with before we deforested."

In addition, Holmes adds, recent research suggests the Amazon may be reaching the point at which it is emitting more carbon into the atmosphere than it is absorbing. The Brazilian region of the Amazon, which is the largest area, may already be a small carbon source to the atmosphere.

“The Amazon, overall, still seems to be a small carbon sink, but we're getting close to that point where it's going to be a net-carbon source."

Max Holmes, acting president and executive director, Woodwell Climate Research Center

“The Amazon, overall, still seems to be a small carbon sink, but we're getting close to that point where it's going to be a net-carbon source,” Holmes warns.

With all this dire news, it may seem like there is little we, as individuals, can do to help, but this is not entirely true.

“We can think about what we're eating. We can eat less meat,” Holmes says. “Another thing we can do is waste less food. We should do that anyway. But, yeah, do you want to protect the Amazon forest? Waste less food, eat less meat.”

This article is by Adam Wernick, based on an interview that aired on Living on Earth from PRX.