Trees are great - they’re big, they’re pretty, and some of them give us food.

And since plants, including trees, turn carbon dioxide into their food and our oxygen, it makes sense that people are all, like, “let’s fix climate change by PLANTING MORE TREES!” After all, they help cool down their surroundings, They provide habitats for lots of critters and suck up carbon dioxide from the atmosphere. What’s not to like?

But to really combat climate change, we need to do more than just planting trees. According to some researchers, we may actually need to start killing them. [INTRO MUSIC] Okay, that was a little dramatic. We’re only talking about killing some trees, and to explain why, we gotta talk about the carbon cycle.

Carbon is everywhere around us. It’s a key building block of every living thing, from blue whales to blueberries from bats to bacteria. But carbon compounds are also in plenty of non-living things throughout the ocean, the atmosphere, and the dirt and rocks of landmasses.

It’s a really normal thing for carbon to enter the atmosphere, usually as carbon dioxide gas. This can happen when living things breathe, When volcanoes erupt, or wildfires burn. And you’re probably aware that carbon dioxide is a greenhouse gas, which means it absorbs and emits infrared radiation, helping our atmosphere trap heat near the Earth’s surface.

Now, greenhouse gasses are not inherently bad. The warmth that they hold in is pretty important for a lot of living things, since without their heat-trapping abilities, our Earth would be a pretty cold rock in space. And at least on a deep time scale, the short- and long-term processes of the carbon cycle naturally balance things out.

When carbon dioxide is  released into the atmosphere, it gets removed from it in lots of ways, as well, like dissolving into ocean water, or being turned into sugars as plants photosynthesize. That cycling of carbon throughout the planet ideally keeps things in balance. But the current problem is that humans are burning so many fossil fuels that we’re skewing that natural balance.

We’re releasing way more carbon dioxide into the atmosphere than the carbon cycle can handle, which has all kinds of side-effects like warming the planet and acidifying the oceans. So that’s why scientists are trying to find any way they can to pull more carbon out of the atmosphere to tip the scales back toward normal. These methods are generally called carbon dioxide removal, or CDR for short.

The high tech CDR methods we’ve developed so far are expensive. It’s been estimated that they can cost between $100 to $300 per ton of carbon dioxide that they process, which gets pricey when you think about the gigatons of problematic CO2 we’re dealing with. And that’s why, when faced with a price tag that astronomically high, you’d think that the next best option would be to just chuck a bunch of trees out into nature and let them do their thing.

But even though forests remove billions of tons of carbon dioxide from the atmosphere every year as trees photosynthesize and grow, it’s not as simple or as cost effective a solution as it sounds. For one thing, planting trees isn’t as easy as just digging a hole wherever you want and putting in a seed. technically it is that easy. But it’s not a great long-term strategy because ecosystems are complex things, and need more than just trees.

Carbon storage looks different in a forest versus a grassland, which has mostly grasses and few trees, or a savanna, which is hot and desert-like. So planting trees in places that aren’t suited for forests would just mess up the balance of the existing carbon cycle in those places… not to mention fundamentally alter their habitat. Not to mention the trees might not grow.

Also, you just can’t plant whatever tree you want, wherever you want! Different trees evolved in  different soils, climates, and regions around the world. Certain tree species might use up water or other nutrients that native plants need to survive, so they cause more harm than good.

Or if you just plant tree seedlings without caring for them, many of them just die. Since decomposing trees release carbon dioxide into the atmosphere, we end up right back at square one. And that’s really the crucial thing here.

Even though forests can remove carbon dioxide from the atmosphere, they release carbon dioxide too. Aside from when they die, their cells also respire  and release carbon dioxide, not to mention all the carbon that’s released when they burn up in wildfires. So they do store carbon, but not forever.

Eventually they either decompose or burn and that CO2 gets rereleased Even if we thoughtfully plant millions of trees, there’s a limit to how much carbon dioxide any one tree can absorb, and they’re relatively short-term storage compared to fossil fuels buried way underground. Which is why we need to look at better options. Like tree burials.

But before we get to that, a quick mid roll Thanks for watching this SciShow video! SciShow, and all of Complexly, has always benefited from people like you watching our stuff, telling your friends about it, and generally supporting our work. And we want to keep SciShow going and you are a vital part of that equation.

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Check out the links below to support us and get your very own SciShow postcard, signed by me and the rest of the SciShow hosts! You can Find them at complexly.com/postcard. And we’re back In a paper published in September 2024, researchers sort of accidentally stumbled on what could be a major solution to that problem of carbon storage being short term, in the form of an old, preserved, dead tree.

More specifically, an Eastern red cedar log buried 2 meters underground in Quebec, Canada. The team was digging a trench into compact clay soil to prototype an idea they called a wood vault. Basically the idea was that you could bury a tree in a grave that would protect the wood from decomposers like microbes, fungi, or insects that need oxygen to survive.

Without decomposers to break down that dead tree, the carbon would stay stored in the wood, rather than being re-released into the atmosphere. While they were digging their tester tree grave, they stumbled across a tree that was already buried down there. And with some carbon-14 dating, that it was about 3,775 years old.

That’s really old This millenia-old tree resented the perfect opportunity to test the idea that buried trees could store lots of carbon for a very long time, since they could compare that very old tree to a fresher one and see if it really did hang onto its carbon for all that time. And they estimated that the buried tree only lost around 5% of its carbon over thousands of years! So how’s that for a proof of concept?

They didn’t even have to do any of the burying or waiting themselves! And yeah, the researchers suggest that we could consider  cutting down some living trees and then burying them in oxygen-poor clay soil, though a lot of the wood that’d get buried would be stuff that was already broken, from things like storms, city tree removal, or natural wildfires. In fact, they estimated that an optimized version  of this wood vaulting system could store around 10 billion tons of carbon dioxide every year for around 30 to 100 dollars per ton, which is at the lower end of the estimates for higher-tech carbon storage options.

So one fix to our climate woes could be as low-tech as an chainsaw and a back ho, and the best place to put trees when we want to slow down climate change is underground. But we still love the trees that are above ground, too. We are happy for them, we don’t want them to go away [ OUTRO ]