Planting trees is a good idea and can help with climate change by getting carbon out of the atmosphere — but it’s not going to be enough according to Zeke Hausfather, a contributing author to the IPCC Sixth Assessment Report, the climate research lead at Stripe, and a research scientist with Berkeley Earth.
In a guest opinion piece at The NY Times he warns:
Trees are our original carbon removal technology: Through photosynthesis, they pull carbon dioxide out of the air and store it. They have lately been touted as a climate savior, a way to rapidly reduce the carbon dioxide that has accumulated in the atmosphere as we cut our emissions. A “trillion trees” initiative was launched with much fanfare at the World Economic Forum in Davos back in 2020, and it was one of the few climate solutions embraced by the Trump administration. Planting trees and protecting forests are a major part of many corporate efforts to offset emissions.
But there’s a catch. Carbon dioxide removed from the atmosphere is only temporarily stored in trees, vegetation and soil, while a sizable part of our emissions today, will remain in the atmosphere, much of it for centuries and some of it for millenniums to come.
Trees can quickly and cost-effectively remove carbon from the atmosphere today. But when companies rely on them to offset their emissions, they risk merely hitting the climate “snooze” button, kicking the can to future generations who will have to deal with those emissions.
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Trees are not forever. They live, they grow, they capture carbon — then they eventually die and release it again. Meanwhile, the CO2 already in the atmosphere released by burning millions of years worth of carbon accumulated in fossil fuels is a continuing thumb on the scales.
We have a saying in the climate science world: “Carbon is forever.” Around 20 percent of the carbon dioxide we put into the atmosphere today will still be in the atmosphere many thousands of years from now. This means that to effectively undo emissions, the carbon we take out of the atmosphere needs to stay out. There is a real risk that, in a warming world with more wildfires, with pests preying on trees and with drying soil, carbon in tree plantations could end up back in the atmosphere sooner rather than later. For carbon to be permanently removed by planting trees, forests would have to remain in place for thousands of years. On top of that, the trees would have to be planted on land that would have been forest-free for those same thousands of years had the trees not been planted.
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To make a somewhat clumsy analogy, planting trees to take carbon out of the atmosphere is a bit like making only the minimum monthly payment on high interest credit card debt. Yes, it is paying something of the debt, but if it doesn’t even cover the interest let alone the principle, the debt hole only gets deeper and the total amount paid over time far exceeds the original debt.
Hausfather discusses several ways planting trees in an effort to offset greenhouse gas emissions can be problematic. Unless long-term arrangements to manage tree plantations can be assured, typically contracted for 40-years, the temporary gains can fail to be realized or even lost to fire, pest infestations, drought, etc.
The attempts to rein in emissions and remove carbon from the atmosphere can be gamed in other ways too:
While carbon removal is often conflated with carbon offsets, the vast majority of offsets currently sold pay someone else to avoid emissions rather than removing carbon dioxide from the atmosphere. Offset markets are plagued by hot air, with many actors gaming the system by claiming carbon credits for actions they were already planning to take, such as building a clean energy project or not cutting down a forest they own. In one case, an environmental group even provided offsets that were sold to oil companies, making the dubious claim that they would otherwise allow the forests they own to be logged.
The math is not ambiguous:
It is also increasingly likely that the world will pass 1.5 degrees Celsius — our most ambitious climate target — in the next decade or so. In the recent IPCC report, more than 96 percent of scenarios that limit warming to 1.5 degrees Celsius above preindustrial levels by the end of the century overshoot it on the way there. Once we overshoot 1.5 degrees Celsius, even getting emissions all the way down to zero will not cool the world back down. This is the brutal math of climate change, and it means that the only way to bring global temperatures back down in the future is through the large-scale removal of carbon dioxide from the atmosphere.
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Think of it as the equivalent of putting back all the coal, oil, and plant-based carbon we’ve been burning for centuries. As Hausfather and NOVA point out, the carbon doesn’t go away. It's like continuing to pile blankets on the bed even while you are burning up underneath them. We have to start taking it out of the air or we will keep cooking and it will get worse.
How much?
How much carbon removal will ultimately depend on how quickly and fully we can cut emissions. Most of our models show that to keep warming below 1.5 degrees Celsius, we’ll need to remove around 6 billion tons of carbon dioxide from the atmosphere each year by 2050 — a bit more than annual U.S. emissions today. Over the next 80 years, we may need to remove more than 600 billion tons, an amount greater than 15 years of current global emissions.
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An October 28, 2020 episode of NOVA asked CAN WE COOL THE PLANET? It covered various ways of removing carbon permanently, looked at planting trees, and cutting emissions. Starting about 5 minutes in to the video at the link, there are some graphics that show just how much carbon we are putting into the atmosphere every year — and how much we’re still living with from all the previous years. If you don’t have time to watch the whole thing, at least look at that part
It’s staggering. The biggest problem in facing up to climate change is that we can’t directly see how much carbon we are putting into the air. The graphics NOVA came up with make it a bit clearer.
Bottom line:
1) We have to cut emissions as rapidly as we can to stop digging the hole deeper faster than we can climb out of it.
2) Planting trees is a good thing but not a sufficient thing. We should do more of it but we have to regard it as only a partial answer.
3) Getting to zero emissions is not going to be enough to avoid increased warming. We have to do more.
4) We have to start removing carbon from the atmosphere on a permanent basis and we have to do it to compensate for the amounts we are currently adding AND the carbon we’ve put up there previously.
If you have time, watch Can we cool the planet? It’s a life or death question.