Image: Nathan Stephenson, USGS
A trillion trees, low-tillage agriculture, and a sustainable economy would mean that in about 500 years we would have the level of CO2 about where we want to keep it, probably around 300 ppm.
So we have a trillion tree campaign going on globally. Imagine if we managed to get 100 million trees a week planted, instead of the 63 million total planted by all of the contributors to date. What would that start to look like for the environment and the climate over various timeframes?
Is 100 Million A Lot Of Trees?
That sounds like a stupid question, doesn’t it? 100 million is the definition of “a lot,” most people would say. Some wit would probably say that if you looked in a dictionary for the definition of a lot, a picture a 100 million of anything would suffice.
However, the scale of the problem is large. There used to be about 6 trillion trees on the planet, and we’ve cut down about half of them. A Swiss study from a couple of years ago that I wrote about recommended planting a trillion trees as a major step in addressing a portion of climate change. A trillion is a lot more than 100 million, about 10,000 times more. And that trillion trees would basically just keep up with our current emissions, not deal with the 99% of emissions that are already in the atmosphere. Yeah, about 4,000 billion tons of excess CO2 over 300 years, and only about 1% more per year. Lots of legacy CO2. Those trillion trees would soak up about 25 years worth of our current emissions over their lives. That gives us breathing room, but still doesn’t solve the problem.
When I say that 100 million isn’t a lot of trees, that’s in context of the need being 10,000 times higher. That suggests that it would take about 200 years with a couple of weeks vacation each year to get to a trillion trees.
For some more context, China is one of the biggest and now is one of the richest countries in the world. And it has 1.4 billion tree planters, if it wants to mobilize its people to plant trees. The country has been running the most aggressive reforestation program in the world since 1990, mostly because it ran one of the most aggressive, if unintended, deforestation programs in the world prior to that. In 30 years, China has planted about 40 billion trees, about 4% of that trillion trees target, covering an area the size of France. So yeah, getting to 100 million trees a week is tough.
Our problem is a little more urgent than something that takes 200 years. Planting a trillion trees in the next 40 years would be more like it. But still, that’s only five times as many trees per week, and let’s be clear, if someone were to plant 100 million trees a week, that would be stellar as a contribution. Just insufficient to the scale of the problem by itself.
So having set context, let’s ask the next question.
What Makes A Good Tree?
This sounds like another stupid question, I know. But you really should read The Hidden Life of Trees: What They Feel, How They Communicate — Discoveries from A Secret World: Wohlleben, Peter, Flannery, Tim, Simard, Suzanne, Billinghurst, Jane. Great book, and very enlightening.
Here’s what makes a good tree, per the book. It is prevented from growing rapidly by being starved of nutrients and light by mature trees for 80 or more years. It’s kept on life support by mature trees via the root network, basically a consistent intravenous drip. As a result, it grows incredibly fine, dense rings and is amazingly strong, resilient and self-healing. When a mature tree dies and an opening in the canopy is created, the lucky good tree shoots upward rapidly, fighting with all of its fellow saplings for the maximum amount of the bounty of light and nutrients until it fills the gap and starves its children for decades in return.
A good tree, by nature’s standards, is hundreds of years old and grows only in forests. We don’t have hundreds of years, so that definition isn’t going to help us much.
The definition that most people have used for the past couple of hundred years is that a good tree is 40–80 years old, grew sufficiently isolated from other trees that it could attain size quickly, and big enough to be cut down and put through a sawmill and turned into lumber for various uses. Yeah, that’s humanity’s definition of a good tree, one that doesn’t grow into nature’s version of a good tree. Another definition of a good tree we tend to use is that it provides shade on paths and roadways for pedestrians and cyclists, its trunk sticking up out of holes in the concrete, and reduces the urban heat island effect. Yeah, that tree isn’t a good one by nature’s definition either.
But that said, we’ve cut down three trillion good trees so we have a lot of bare land that could support trees, and they are an amazing technology that’s sitting around. I wrote about them recently, saying that they were this great self-assembling technology that captured carbon without us having to do much more than drop them on the ground.
If we plant the right kind of trees in the right places and then leave them alone, eventually they will turn into a mature forest that does a pretty good job of being resilient, self-healing, self-maintaining and a good carbon sink.
Which is a bit of a sticker. Another maybe silly question is in order.
When Is A Tree A Good Carbon Sink?
After all, trees eat CO2 from the air and turn it into the organic polymer we call cellulose. Pretty neat trick.
When a good tree by nature’s definition is alive, it has a rich root system that interlocks with a dense mat of fungal threads under the soil, a mycelium network. That fungal network has a protein on it called glomalin, and that protein is the pathway to long term soil carbon sequestration. If you leave the soil and its mycelium network alone, in about 150 years it permanently turns carbon molecules from the air into underground chemical deposits that are stable and don’t rot.
And when that good tree dies in a mature forest, it is quickly turned into nutrients for other trees and plants, basically being strip mined of its carbon. A good tree in a mature forest has been feeding carbon into the glomalin pathway its entire life of hundreds of years, and the carbon left in its massive, dense trunk and branches is grabbed by other plants in many cases. Even the rotting wood left behind decomposes aerobically (that’s in the presence of oxygen, not in a fitness studio) and turns into CO2, which the trees around it breathe, so a lot of that CO2 gets hoovered up by other trees.
But we aren’t planting good trees in a mature forest. We’re planting 100 million seeds or seedlings a week on ground that had trees on it until we cut them all down and throw them into sawmills.
Not optimal conditions for a good tree, but definitely conditions where trees that are good by our definitions can be made to work. There are some kickers.
First of all, in many cases the mycelium network has been screwed up. Denuding a bunch of ground of trees that have been on it for ten thousand years really wreaks havoc on an ecosystem above and below the ground. It’s entirely probable that the fungal species which are best adapted to glomalin pathways with trees will take decades or hundreds of years to find their way back into our new purpose-built miniforest. As a result, the glomalin pathway won’t be kicking into gear quickly enough, and that 150-year timeframe is probably closer to 250 or 300 years for long-term carbon sequestration. So just dropping seeds or firing seedlings into the ground from tree-planting drones doesn’t solve the entire problem.
That’s solvable however. It’s pretty easy to spread fungus, and it’s probable that it could even be in the seedling dart so it could be a one-step process. You do want to get the right fungi, however, and that probably needs to be tailored to tree species and the region, so some planning is required.
Secondly, the seedlings aren’t surrounded by mature trees that protect them, feed them intravenously and allow them to grow slowly enough that they are incredibly dense and resilient. Instead, they are the weak versions we see along roads in our towns and cities, growing too fast and as a result much more subject to being blown over by strong winds and damaged by insects. Pine borers love reforested pine in part because the trees are so easy to burrow into.
That means that a lot of the trees are going to die early because they aren’t as resistant to insects and wind. And because it isn’t a mature forest that eats its dead as efficiently, when they die, a lot of the carbon embodied in their not-so-dense trunks and branches will just go back into the atmosphere when they die.
Third, you might want to avoid doing what forestry firms have been doing with reforestation programs since they began, which is to plant fast-growing monocultures of trees that they can harvest as soon as possible and turn into more chopsticks and toilet paper. Monocultures are problematic in nature because they are so susceptible to ailments and insects. A diverse forest can be swept by an insect plague and be left with a lot of trees, but a monoculture gets turned into a dead forest.
So this all suggests two paths for planting the 100 million trees a week. The first path aims to recreate resilient mature forests and good trees by nature’s standards. That ensures that carbon that gets eaten, stays eaten. The second path is to do reforestation the way we have been doing it for a hundred years, which is to blast in a lot of seedlings on deforested land, then return and harvest them in 40–80 years.
Both have merit. One is ‘better’ than the other as a long-lasting carbon sink, but harder to create. But the normal reforestation model gives us a 40–80 year carbon sink, and we can harvest a lot of it for engineered hardwood and other durable wood products that will sequester a lot of that carbon for potentially hundreds of years. And it’s likely that they are a continuum, not separate things. You can imagine a mixed reforestation program, with portions meant for complete harvesting and replanting, and portions intended to be groomed into mature forests. And you can easily imagine selective harvesting of specific trees that tries to not destroy the trees around them.
The point of this is that 5, 50, and 500-year timeframes really depend on which models you choose, and how they are maintained through time.
Given the scale of the problem, it’s clear that in 5 years, only about 2.5 billion trees would have been planted, or about 2.5% of the scale necessary to make a big difference for climate change. That’s still good, but it’s not particularly meaningful by itself. After 5 years, there will be a lot of seedlings and saplings where they didn’t exist before, and in many cases they’ll be starting to turn into an ecosystem. But that’s just a starter kit.
After 50 years, about 250 billion trees would be in place. That would be starting to make a difference. A lot of them would be mature, assuming that pine borer beetles and wildfires didn’t take them prematurely, and the ones that survived would be mothering little baby trees, as nature does. That would be in the range of keeping up with something like a quarter of our annual emissions, assuming we kept going with our idiocy. Assuming we actually decarbonize energy, transportation and everything else, that actually means the trees are drawing down on the 300 years of legacy CO2, which is much better.
Yes, if you started planting 100 million trees a week now, and the world decarbonized, in 50 years, atmospheric CO2 would be going down instead of up.
Not quickly, because the Rome of our global warming problem wasn’t built in a day, but going down. That would be a major win.
But note that it probably wouldn’t make much of a difference to temperature and sea level rise projections for 2100. It would keep us in the median band of UN IPCC projections, maybe RCP4.5, and maybe even RCP2.6. It would avoid RCP8.5 and its devastating results.
And it would make a big difference for 2200, 2300, and 2400.
So let’s look at the 500-year projection.
Let’s suppose you planted 100 million trees a year for 200 years, carefully tended the forests, harvested a lot of the wood in a sustainable manner using electrically powered machinery, and turned it into durable wood products instead of paper napkins and disposable chopsticks. And suppose we decarbonized the world by 2060 or so, so we had stopped contributing to the problem. And suppose we also fixed agriculture so that it didn’t keep destroying the glomalin pathway.
Then the trillion trees, the low-tillage agriculture, and the sustainable economy would mean that in about 500 years we would have the level of CO2 about where we want to keep it, probably around 300 ppm. There would be an international monitoring and governance agency that would keep tabs on it to make sure it wasn’t dropping into glaciation territory or creeping up into warming territory. We might burn some fossil fuels some years in controlled circumstances to keep atmospheric CO2 at the right level.
It would be the intentional Anthropocene, as opposed to the unintentional one we stumbled into. We would be governing our climate as opposed to wrecking it.
Wouldn’t that be nice?
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