Exaggerating how much carbon dioxide can be absorbed by tree planting risks deterring crucial climate action

Exaggerating how much CO2 can be absorbed by tree planting risks deterring crucial climate action
Credit: Amenic181/Shutterstock

Planting almost a billion hectares of trees worldwide is the "biggest and cheapest tool" for tackling climate change, according to a new study. The researchers claimed that reforestation could remove 205 gigatons of carbon dioxide (CO2) from the atmosphere—equivalent to about 20 years' worth of the world's current emissions. This has been criticized as an exaggeration. It could actually be dangerous.

While the paper itself included no costs, the researchers suggested a best-case estimate of just USD$300 billion to plant on 0.9 billion hectares. That's less than USD$1.50 per tonne of CO2 removed. More on the costs of removal through reforestation put the figure closer to USD$20-50 per tonne – and even this may be optimistic at such large scales.

Our research suggests that the promises implied in such studies could actually set back meaningful action on . This is because of what we call "mitigation deterrence"—promises of cheap and easy CO2 removal in future make it less likely that time and money will be invested in reducing emissions now.

Why would anyone expect governments or the to invest in , or like high-speed rail, at costs of tens or hundreds of dollars a tonne if they—and shareholders and voters—are told that huge amounts of CO2 can be absorbed from the atmosphere for a few dollars a tonne by planting trees?

Why should anyone expect and airlines to reduce their emissions if they anticipate being able to pay to plant trees to offset everything they emit, for the paltry price of USD$1.50 a tonne. If studies like this suggest removing carbon is cheap and easy, the price of emitting carbon for businesses—in emissions trading schemes - will remain very low, rather than rising to the levels needed to trigger more challenging, yet urgently needed, forms of reduction.

A false carbon economy

The promises of cheap and powerful tech fixes help to sideline thorny issues of politics, economics and culture. But when promises that look great in models and spreadsheets meet the real world, failure is often more likely. This has been seen before in the expectations around carbon capture and storage.

Exaggerating how much CO2 can be absorbed by tree planting risks deterring crucial climate action
Tree planting is cheaper but less effective at reducing emissions than building zero-carbon infrastructure like electric high-speed rail. Credit: Pedrosala/Shutterstock

Despite promises of its future potential in the early 2000s, commercial development of the technology has scarcely progressed in the last decade. That's despite many modeled pathways for limiting global warming still assuming—increasingly optimistically—that it will be deployed at a large scale in coming decades.

This model of tackling climate change goes hand in hand with another tool—pricing carbon emissions. This potentially allows companies to go on emitting by paying someone else to cut emissions or remove CO2 elsewhere—an approach called climate offsetting. But offsetting makes exaggerated promises of carbon removal even more risky.

Tree planting financed through offset markets would guarantee the polluter could continue emitting carbon, but the market couldn't guarantee removals to match those emissions. Trees might be planted and subsequently lost to wildfire or logging, or never planted at all.

Trusting in trees to remove carbon in future is particularly dangerous because trees are slow to grow and how much carbon they absorb is hard to measure. They're also less likely to be able to do this as the climate warms. In many regions of the world but particularly in the tropics, growth rates are predicted to fall as the climate warms and devastating wildfires become more frequent.

Relying on trees to absorb CO2 from the atmosphere in the future also appears misleadingly cheap because of the effects of economic discounting. Economists discount the current value of costs or benefits more deeply, the further in the future they occur. Models which determine the cheapest mix of policies available all use some form of discounting.

When researchers add carbon removal options like to these models, they tend to generate pathways for slowing temperature rise which reduce the role of short term action and replace it with imaginary removals late in the century.

This is because discounting over 30 to 60 years makes the removal options look incredibly cheap in today's prices. Priming models to focus on minimizing cost causes them to maximize the use of discounted future removals and reduce the use of more expensive near term emissions reduction.

I am not arguing against reforestation, nor for a purely technological response to climate change. Trees can help for many reasons—reducing flooding, shading and cooling communities, and providing habitat for biodiversity. Incentives for reforestation are important, and so are incentives for removing carbon. But we shouldn't make trees or technology carry the whole burden of tackling change. That demands moving beyond technical questions, to deliver immediate political action to cut emissions, and to begin to transform economies and societies.

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Jul 13, 2019
Your entire article slams reforestation as a solution to climate change, yet you try to backpedal during the last paragraph to make claims on the benefits of reforestation? No one, that is for reforestation claims that it will work alone. Of course 'we' as in everyone on earth need to reduce the emissions that are polluting our air from our vehicle emissions, to factory/warehouse emissions, and agriculture emissions. What you're failing to realize is that reforestation is only one piece of the puzzle. The 'trees' and all other plants/crops will play a huge part in the removal of carbon from our atmosphere, but what will truly remove carbon from the atmosphere and retain it is the soil. Now, speaking of this issue. What is more important than reforestation is converting the Agricultural Industry to a no-till farming process. This will preserve the soil over the entire land of every farm that exist. Soil pulls carbon out of the atmosphere at large levels and retains it to feed to crops.

Jul 13, 2019
The AGW Cult can't even get their lies straight.

Jul 14, 2019
But deniers keep their lies straight, repeating hundreds of them, often decades after they were debunked. The only cult is the one of denial, based strictly on belief of myths and lies about the science

Jul 14, 2019
127146 -- Plants and other living things are part of the natural active or fast carbon cycle. All the components of that cycle give and take carbon. The oceans, atmosphere, soils and living things. They tend to maintain a kind of balance in the carbon cycle.
However, Fossil Fuels only give and don't take back carbon. A one way street. And fossil fuels emissions are 65% of human caused CO2 emissions.
All land usage issues combined are about 30%, including deforestation, unsustainable farming and livestock practices, loss of wetlands, mangroves, etc.

Fossil fuels emissions are Completely Additional carbon, that does Not belong in this fast carbon cycle.
Fossil fuels are carbon that nature sequestered away in the
Earth over 10s of millions and 100s of millions of years, locking it out of the carbon cycle.
Humans are now putting all that sequestered carbon into the
carbon cycle in a few centuries - a nanosecond in geological time scales, upsetting the carbon cycle.

Jul 14, 2019
127146 -- "What is more important than reforestation"

Stopping Burning Fossil Fuels

see here

The Carbon Cycle

"Without human interference, the carbon in fossil fuels would leak slowly into the atmosphere through volcanic activity over millions of years in the slow carbon cycle. By burning coal, oil, and natural gas, we accelerate the process, releasing vast amounts of carbon (carbon that took millions of years to accumulate) into the atmosphere every year. By doing so, we move the carbon from the slow cycle to the fast cycle. In 2009, humans released about 8.4 billion tons of carbon into the atmosphere by burning fossil fuel."


Jul 14, 2019
"Your entire article slams reforestation as a solution to climate change, yet you try to backpedal during the last paragraph to make claims on the benefits of reforestation?"

No. It was not backpedaling. No one says planting trees won't help. The recent spate of articles claiming it will solve everything are greatly exaggerated. And it puts off cutting emissions now.
There isn't time to wait for the trees to grow. Yes, planting now will help down the road, but we need drastic action reducing fossil fuels Now.

Jul 14, 2019
It's beyond amusing, what jackasses the AGW Cult takes their Chicken Littles, for.
The fact is that the oceans, release and sequester most of the planet's CO2.
Planting forests, is beyond idiotic, since the Cult will never be able create the diversity that's essential for a healthy ecological system. After all, these are the geniAsses whose "solution" was bio-fuels from food crops.

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