A fundraiser called TeamTrees was recently started by a group of YouTube content creators with the goal of raising $20 million by the end of the year, which will go towards planting 20 million trees. While trees provide lots of environmental benefits besides sucking carbon dioxide out of the air, the ostensible reason for planting these trees is to fight climate change. When I heard about this fundraiser, it made me curious: how much will planting 20 million trees help? None of the folks that are part of the fundraiser seemed to address this question in their announcement videos, so I figured I’d do some rough estimates myself.
A note up front: just because I’m taking a critical look at how much the fundraiser will help doesn’t mean I think it’s not worth donating to or that it’s a waste of time/money/energy. I donated to TeamTrees, and I make monthly donations to a few different environmental organizations. Please read through the full post before making assumptions about what I think of the efficacy of the fundraiser.
One way to approach this question is to look at how many trees there are in the world. According to a research paper in Nature, there are about 3 trillion trees on Earth, and there were roughly 6 trillion trees at the beginning of human civilization. Thus, humans could be considered responsible for cutting down or otherwise killing roughly 3 trillion trees. From this perspective, 20 million trees seems like barely a drop in the bucket: we’d be restoring about 7% of 1% of 1% of all the trees we’ve cut down.
We can also take a more direct look at the effect of planting trees on the amount of carbon dioxide (CO2) in Earth’s atmosphere right now. Atmospheric CO2 is the main reason we’re experiencing global warming – I won’t go into the details in this post, but essentially to stop climate change we’ll need to stop putting more carbon dioxide in the atmosphere. Atmospheric CO2 is measured in parts per million, or ppm. Currently, Earth’s atmosphere has about 410 ppm, which means that for 1 million air molecules, about 410 are carbon dioxide. Prior to human civilization, atmospheric carbon dioxide was at around 280 ppm. So we’ve been responsible for an increase in CO2 of roughly 130 ppm. A 1 ppm increase in CO2 corresponds to roughly 7 trillion kilograms of carbon dioxide.
So the question then becomes, how much CO2 does a tree take out of the atmosphere? Some rough estimates are that a tree can absorb about 20 kg of CO2 per year while it’s growing and about 1000 kg of CO2 over the course of its life. Assuming that each of the 20 million trees absorbs 1000 kg of CO2, all the trees combined would absorb 20 billion kg of CO2 – far short of the 7 trillion kg required to reduce atmospheric CO2 by just 1 ppm.
These calculations might seem discouraging, and they explain why none of the TeamTrees participants made a video about them. It will take a lot of work to stop global warming – so much so that planting 20 million trees would be a rounding error within a plan that could actually reduce atmospheric CO2 by the ~100 ppm required to return us to pre-industrial revolution levels.
Does that mean that TeamTrees is bogus and shouldn’t be bothered with? Definitely not. For one, trees provide benefits beyond just absorbing carbon dioxide. But beyond that, planting 20 million trees will ideally be viewed as a first step. If you donate to TeamTrees and then go back to living a high carbon footprint lifestyle guilt free, then TeamTrees isn’t doing much good. On the other hand, if you donate to TeamTrees and continue to think about your carbon footprint in the future, reducing your consumption over time and contributing to environmental efforts long after the 20 million trees have already been planted, then TeamTrees can really be viewed as a positive force against climate change. There will be a lot more work required after the 20 million trees get planted, but that doesn’t mean they’re not worth planting.
Hi Lee,
I noticed this post and thought I would comment. I agree with your conclusion about the efficacy of planting trees as a strategy to reverse global warming, mostly. If we want to fight climate change it helps to get back to basics, The Keeling Curve ( https://en.wikipedia.org/wiki/Keeling_Curve ) holds much of the answer to framing the right engineering question. The curve shows us that summer in the northern hemisphere is a powerful tool for drawing down global CO2! The problem is winter…or is it? Something happens each year to derail this massive climate-change-reversing freight train of summer. Fungus breaks down the wood and returns the CO2 to the air. We might ask rather than plant more trees can we plant less fungus?
If we could snap our fingers like Thanos and stop 50% of all microbial decomposition of wood we would rapidly be facing a “snowball” earth climate catastrophe based on the Keeling Curve. An intriguing climate engineering question; “If a well-meaning Thanos wanted to stop climate change on earth what percentage of microbial decomposition of cellulose/lignin/hemicellulose would he stop with the snap of his fingers?”
Interesting question. Looking at the Keeling curve, it seems like there is a roughly 5 ppm swing seasonally, while the increase in CO2 is about 2 ppm annually. As a back of the envelope approximation, that means stopping ~40% of microbial decomposition every winter would cancel out the carbon dioxide being added to the atmosphere through burning fossil fuels.
Though this assumes that all the plant life on Earth is in the northern hemisphere, which is not accurate. Unless Thanos could only snap away microbial decomposers in the Northern hemisphere, we’d want him to stop a smaller percentage.