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Comment by zxcvbn4038 | Hacker News Reader

I keep hearing about farmers in poorer countries cutting down mature forest in order to profit by planting more saplings. That completely defeats the purpose, you think people would have caught on by now and put in checks against that.

Planting trees at the wrong time of year also seems to be a constant issue. It’s not just an issue of sticking something into the ground. Timing and location matters. A single tree might make hundreds or thousands of seeds each year but the number that sprout and survive to adulthood is a very small fraction, there is a lot that needs to go right.

Once all that happens it often takes several years before you start to realize the carbon benefits. So really things like “carbon credits” really need to be based on trees surviving to adulthood, not just sticking a sapling in the ground someplace. But once you get to that point there is ongoing benefit.

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https://en.wikipedia.org/wiki/Perverse_incentive

> The term cobra effect was coined by economist Horst Siebert based on an anecdote of a (possibly ahistorical) occurrence in India during British rule.[2][3][4] The British government, concerned about the number of venomous cobras in Delhi, offered a bounty for every dead cobra. Initially, this was a successful strategy; large numbers of snakes were killed for the reward. Eventually, however, enterprising people began to breed cobras for the income. When the government became aware of this, the reward program was scrapped. When cobra breeders set their now-worthless snakes free, the wild cobra population further increased.[5]

I first heard of this idea from Terry Pratchett, who as well as explaining the problem gave a possible solution:

> Shortly before the Patrician came to power there was a terrible plague of rats. The city council countered it by offering twenty pence for every rat tail. This did, for a week or two, reduce the number of rats – and then people were suddenly queuing up with tails, the city treasury was being drained, and no one seemed to be doing much work. And there still seemed to be a lot of rats around. Lord Vetinari had listened carefully while the problem was explained, and had solved the thing with one memorable phrase which said a lot about him, about the folly of bounty offers, and about the natural instinct of Ankh-Morporkians in any situation involving money: ‘Tax the rat farms.’

—Terry Pratchett, Soul Music

This has an historical precedent:

https://www.atlasobscura.com/articles/hanoi-rat-massacre-190...

posted multiple times on HN, last time 4 months ago: https://news.ycombinator.com/item?id=27264816

All metrics of scientific evaluation are bound to be abused. Goodhart's law [...] states that when a feature of the economy is picked as an indicator of the economy, then it inexorably ceases to function as that indicator because people start to game it.

https://en.wikipedia.org/wiki/Goodhart%27s_law

Programs to reduce exploding wild boar populations in the US had the same problem.

I recall most trees are actually counted by the number and not necessarily volume or any other more reasonable metric. For example here in the Netherlands you can easily cut down vast amount of trees as long as you simply replant the same amount of trees. Diversity doesn't matter and it results in images of seeing incredibly dense populated pine trees, that are so close they're even choking each other and just the tips survive. Suffice to day these "forests" don't really live long.

Sometimes I think some of the most valuable assets will be century old trees.

A mature forest doesn't remove much CO2 from the atmosphere. A growing one does. Depending on what you do with the felled lumber, it could be much better for the environment to chop down a forest and plant a new one.

A mature forest not only hosts diverse ecosystems, it also produces a beneficial local climate.

It's also a gross oversimplification to look at CO² balance by absorption by trees only. Floodplain forests, forested swampland and broad-leafed trees also store massive amounts of CO² even when the forest is mature.

But more importantly, mature and healthy forests offer a broad range of benefits beyond binding CO². Reducing the value of forests and the associated ecosystems to CO² is a flawed approach. There's many more factors involved, including preservation of fresh water.

>CO²

Nitpick here: I see you've gone into the effort of stylizing the 2, but chemical formulas are supposed to be numbered using subscripts, not superscripts.

CO₂

This is a non intuitive result, and people is confused often by that, but adult mature [1] trees grow much faster than young trees. Faster here does not mean taller, means bigger.

[1] I'm not talking about dying trees, mature does not mean dying necessarily.

A mature forest isn’t just filled with mature trees you get the full lifecycle and close to zero net carbon capture.

It’s not obvious when walking around because adult trees significantly outnumber dead ones, but trees decay in a tiny fraction of their total lifespan.

Decay can sequester carbon in the right ecosystem and physical geography. Western Europe has its topsoils thanks to centuries of wild mature forest.

Do you have a source, both ways seem to have some logic to them (a larger growth is a smaller percentage growth for a large tree, for example - adding 1% to a massive tree is better than 10% to a tiny tree), but also we're used to new life increasing size far faster ...

Actually, I might tree rings not getting smaller as a tree grows taller is probably enough evidence to see that the carbon added increases over time? Would be nice to have a rigorous source to review too?

do you have some science to back up this claim? i’ve read a bit about this as an layperson and the mature vs young forest debate seems kinda inconclusive. but it also seems like keeping a mature forest’s ecosystem in tact is better than clearcutting and planting new trees that supposedly grow faster and capture more carbon. by clearcutting, you’re removing and releasing a lot of the ecosystem (mushrooms and such) that also play a part in carbon capture and storage. capturing carbon is only one part, from what i understand, a mature forest’s ecosystem does a lot to retain it, too.

'grow faster' is a bit of a vague statement. What we should be talking about is biomass added, which is what sequesters carbon. Older trees unequivocally add mass at a faster rate, which is geometrically obvious when you consider that old growth tree rings add about the same radius each yeah that young growth trees do, and then consider that area of a circle grows with the square of radius.

see:

https://news.unl.edu/newsrooms/today/article/study-finds-lar....

Maybe the middle way should be not clear cutting but punctual culling so you'd try to get best of both worlds... and getting closer to regenerative agriculture as well.

That's such an incredibly short-sighted and single-tracked view on what is "the environment". Planting trees will not magically fix the climate, and carbon sequestration is not the solution to all our problems. Destroying ecosystems for the sake of capturing more carbon makes no sense, if for no other reason that it reduces the chance of survival of the new trees. You also can't lose focus from the end goal of why we're trying to capture CO2. The goal is to save the environment.

> A single tree might make hundreds or thousands of seeds each year but the number that sprout and survive to adulthood is a very small fraction, there is a lot that needs to go right.

While this is true, I think you are stretching this to fit your particular narrative. Seedlings that sprout from a nut that "didn't fall far from the tree" have a lot of things going against it. The shade of the mature trees around it prevent it from getting enough sunlight. There are other factors that contribute as well.

Consider the cottonwood tree. Its seeds drift in the wind (definitely out of the range of the tree's roots/shade), and there's lots of seeds.

And yet the GP's point stands; the vast vast majority of them do not sprout, or, if they do, do not make it to maturity.

It makes sense that planted trees are not thriving in ecosystems where there wasn't already trees naturally. If the conditions were so good for tree growth, you would have a lot of trees there already.

But, this brings to mind that there are places where there once were forests that humans destroyed. Why don't those locations quickly re-forest themselves?

Because, in the process of deforestation, humans destroyed the entire ecosystem that made said forests possible. Nature can't repay that ecosystem debt all that quickly and it's not sped up much by way primates plopping saplings into the soil for money and calling it a day.

Climate change is the mother of all collective action problems and one of our great filters. I dream that one of the descendants of my nieces and nephews will pass through the ensuing population bottleneck.

[Edit, removed speculation on tree growth rates and repercussions.]

It must be a massive temptation for the poor living near massive, high-value, tropical hardwoods to just go and fell them.

Yes, carbon credits should be based directly on mass of carbon taken from the air, we can measure forests, seems like it could be? Saplings need caring for too, there is ongoing benefit and ongoing cost.

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