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Comment by JoeAltmaier | Hacker News Reader

A healthy old-growth forest is maybe 100 trees per acre.

A 'naturally regrowing' forest may be 400 trees per acre. They're scrub trees, none of the ever getting very large, unhealthy and scraggly and broken by every storm.

It takes maybe a century of trees dying, giving one of their cohort a chance to get ahead of the others, then shading them and 'thinning the herd' until you have a stable population. Then, they're still not very healthy because they 'grew from scrub'.

They have to then die of natural causes one at a time and be replaced by a single healthy one. Maybe another 50 years. Finally you have a stable healthy forest.

Or, you can just plant 100 trees per acre in a grid. And mow the volunteers until you have what you want. 20 years maybe.

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(disclaimer, I am part of a Climate&Energy R&D lab)

The goal is not really to produce a set of big trees, but to maximize the amount of carbon you can suck out of the atmosphere per year, heavily weighted to the near future. As a result, producing an old growth forest is not the correct metric (if you are optimizing purely for climate).

A stable forest (from purely a climate perspective) is also not the right optimization. Ideally, you'd lock away the carbon outside of the biosphere, instead of letting it get recycled.

Doesn't hurt explicitly mentioning the biodiversity crisis is, just like the climate one, also a pressing issue. And when it comes to solutions revolving around forests (or a collection of trees if you wish), it's the area where both clash: optimizing for one will be less ideal for the other. Personally I feel like in such cases it would be wise to strive for a solution which is sliglty in favor of biodiversity, just because for the climate there are a number of other solutions which have a larger potential effect.

I'm saddened that the concern over carbon in the atmosphere seems to eclipse the biodiversity crisis in the public eye. In my opinion biodiversity is a far more pressing issue and loss of biodiversity is much harder to recover.

We have a mixed redwood, pine and misc forest. What do we do to (1) get rid of the non-native species, and (2) capture lots of carbon in the process?

We’d like to make sure the redwoods survive. They’re all under 100 years old, so some are big, but not massive, and we have lots of seedlings.

I’m worried if we cut all the pine down at once, it’ll ruin the microclimate. It’s 10-20F cooler in the forest than in the field, with much more water from fog drip, etc.

What species of pine are they? Pines tend to grow fast but are short lived but I would only remove them if they are >40cm dbh. For the rewood the only thing you could do would be to thin and remove competition if there are trees to close, you could also prune if you want. (I study forestry science in New Zealand where we grow a lot of Californian species)

Have you considered something different for climate; mass production of climate change resistant (ie heat/acid) photosynthetic plankton and releasing to ocean?

How does it compare to trees?

i'm always a skeptic of muddling too much with nature (as opposed to just getting out of natures way and letting it do it's thing) Maybe its because I've read too much science fiction, but the first scenario that pops into my head is that we engineer some super plankton that grows out of control and smothers the ocean, not letting light filter down, and basically killing all ocean life. Kinda like a green ice-9 if you will...

A comforting thought for this sort of thing is that it would have happened naturally already, if it were possible at all. We can assume that we're broadly in a 'low energy state', and there's no tiny change that will cause a massive permanent shift. Similarly, Ice-9 can't be real or Earth would be covered in it, and we weren't going to set the atmosphere on fire at Trinity because Earth's already been hit by huge asteroids that didn't.

So sending in logging trucks, tractor saws, and burning all that fossil fuel to "reduce atmospheric carbon" only to have weakling brush landscapes that easily burn is the solution?

Hi Chris, do you happen to know of the optimal ways that Mother Nature removes carbon from the air? Something that we could recreate/automate.

I don't know about Mother Nature, but silicate rich (or carbonate rich) rocks weather by sucking C02 out of the atmosphere (or oceans) and it can apparently be accelerated by spreading crushed rocks on fields or beaches.

- https://en.wikipedia.org/wiki/Enhanced_weathering

- https://www.theguardian.com/environment/2020/jul/08/spreadin...

- https://projectvesta.org/

I wonder how many tons of biomass in foliage regrows every single year. All that plant matter is primarily carbon by mass, and most of it probably comes from the atmosphere.

I came here to say basically this. I'm not a scientist but I live in a heavily forested and logged area with 2nd, 3rd and 4th generation forests (ie, logged 1-3 times in the last 150 years or so).

Here's my observation:

- old growth forests are beautiful and amazing, but old - forests that are treated as a renewable resource are productive due to appropriate maintenance (thinning, etc) - forests that were replanted but not maintained are unhealthy and take more than 50-100 years to cycle back to a healthy natural forest - left alone, on the west coast anyway, there is a typical cycle of fast lived quick growing -> slow growing long living species that takes 100's of years to get back to where it was.

I recently built a house on a property that was 3rd gen but abandoned (last logged 30-40 years ago). We wanted to keep as many trees as possible but because the land was never maintained most of the trees were thin and had parasites. The "widow makers" had to go. You could definitely see the progression of different species doing their thing at their own paces. Alders were mostly gone, hemlocks and firs were starting to fall and die and the cedars were starting to take over, but most of those were still young (but healthy).

That's a gross over generalisation. There are many forests that will naturally regrow into healthy forests in 100 years with reasonably high stocking and large trees, I was in one a few weeks ago.

Not sure you'll see great results in every environment. I am not an expert but I can walk in the forests of the northeast and see things don't look super great and we won't ever see old growth like we had here. My neighbor is a 90 year old tree farmer, he's got an ag PHD and we sometimes talk about how the land has changed here (he's been living the same place for around 85 years).

On my desk in front of me sits one of the two viable American chestnut nuts I've found this year from a (barely) surviving tree of the blight. 100 years ago there were over 4 billion of these trees, now it's assumed that maybe 100 or so large examples exist inside the original range ravaged by the blight. There's no point in planting it, the nut I have has likely hybridized with the Chinese chestnuts we have nearby and it's almost certain it would also die from the blight before it reached maturity. Right now there's plans to introduce an engineered variant with a gene from wheat to stop the effects of chestnut blight, but it needs approval: https://www.acf.org/wp-content/uploads/2018/11/Newhouse-f201...

The undergrowth of the forests here are covered by tearthumb (mile-a-minute) and stiltgrass, and I can see dozens of dead ash trees covered in the zigzag scars caused by the emerald ash borer. The large elms were all wiped out before I was born, but many of the dead ones were still standing. We have fast growing tress in the form of things like tree of heaven (aka ghetto palm, which lives maybe 70 years at most), but that's now attracted the latest imported hell: the spotted lanternfly. Not far from me there's huge numbers of eastern hemlock dying off from woolly adelgid, which is manageable but at great expense and effort. What we could plant and have regrow 100 years ago just wouldn't work now for these and many other reasons that much better qualified people should write about.

Ah Dutch Elm Disease! We had a fine old elm in the front yard, a swing on a chain from a large branch with a pit under it from generations of kids scuffing in the dust. Beautiful.

Then Dutch Elm Disease came through Iowa. Our tree lost a lot of new growth, the next year grew a million suckers from the trunk looking like a furry tree, then was dead. The stump when we cut it down could hold all the kids sitting around it (big farm family).

Years later I went to California to school, then bought a house on 12th St in San Jose. Beautiful mature trees lining the street! 60 ft high, a green corridor!

Then they started dropping branches, destroying awning and car hoods. The next year the affected ones grew a million suckers on the truck like huge furry sculptures.

Unknown to me, they were 'Siberian Elm'. The Dutch Elm disease had reached the west coast! It had taken nearly 20 years to travel halfway across the US.

The city removed them all, and it became a sun-blasted street with no relief from the heat. Gone the tunnel of green. Gone all the Elm in the Western US.

Dude its just a comment on HN. Not a textbook.

Pick your own tree, your own scrub density. It depends on the tree of course. But much the same syndrome.

Its a system. Clear cutting a balanced, self regulsting and niche efficient ecosysten and replacing it with grids, monocultures, etc is why we got to the problems we are in today.

We can certainly jump start the process, but the end result needs to be nature as it was before we broke it, or as close as possible. Its the path to an anti fragile, sustainable, biodiverse planet.

*regulating

There was a horror movie that came out a year or two ago, involving haunted woods or somesuch, and I can't tell you anything more about the movie because all I could process was the fact that the 'forest' they showed was trees planted on like a 4 or 5 foot center, in perfect rows. Math says that's somewhere ~2000 trees per acre, which I think is the real horror story.

I'm not sure how you'd even log that. Every tree that dies is going to kill a few of its neighbors, until there are giant triangles of dead trees.

I'm not entirely sure what your objection is here, but if it's that they're too close together I encourage you to visit some of the productive forests in Western Canada. Trees growing (whether naturally or planted) 4-5' on center is pretty normal.

Tree planters put in trees about one every pace. They don't all survive, but they're not all supposed to. As many make it to maturity as the light allows.

I think the objection was that a "haunted forest" sounds like it should be something old and natural and tangled and wild (think the Old Forest near the beginning of Lord of the Rings).

"Haunted pine plantation" just doesn't have the same vibe to it.

If anything pine plantations can feel more haunted with their unnatural uniformity and changes in how far you can see.

With dense planting of that sort you will thin (and get some natural thinning) so that your final crop will be much lower, usually 300-1000 stems/ha compared to 5000+.

These trees were already 8+-10 inches in diameter. Wouldn’t you normally do the thinning much sooner?

At about that time, although at 5000 stems/ha that's a lot of trees that big.

All I can figure is, I know that there's a tree harvesting device that picks the trunk up vertically and cuts it to lengths before dropping it.

Maybe there's a model that's twice as wide as the distance between the rows, and they're going to take out every second row and every other tree. But then it's driving over trunks and leaving an awful lot of logs on the ground behind it...

That's pretty typical for production of paper and OSB.

And in a drought overly dense forest can die wholesale due to insufficient water in the waterbed to support the forest density. See e.g. CA. This is "natural" in the sense that this is how trees have grown since time immemorial. But it's also undesirable if there are humans living nearby.

What makes a forest of young trees ”not very healthy”?

The 'healthiest forest is one with different ages of stands mixed throughout.

Though, this all depends on where you are and what the natural disturbance type and frequency is as well as the natural age of the trees.

Speaking of coastal western old growth, the kind a lot of people think of, giant cedars and stuff. Old growth gets old, like thousands of years old because typically the disturbance types would be windfall and infrequent wildfires from lightning.

These events would cause patches where giant trees fall and crush neighbour trees, fires burn out patches and new growth starts. This means throughout a natural forest you'll get patches with different ages.

This creates the ideal situation for wildlife habitat and other things. New growth forest, not planted in rows as other commenters mentioned, tends to also have a lot of shrubs and underbrush that get killed off in old growth forests. These types of canopies are great habitat for birds and such, they provide forage for deer and bears. While having surviving, intact old growth stands in the forests provides different kinds of habitat. It's also extremely nutrient rich from advanced fungal colonies and hundreds of years of built up decomposing material.

These nutrients are passed from these older trees along mycelium networks to the younger trees and so on.

A healthy ecosystem in general will have a mix of succession stages in a given area. This provides the maximum benefit to life in those ecosystems.

Competition is so fierce that they all grow spindly and weak. A strong storm could flatten the entire grove. It dies back and regrows constantly, no tree ever getting very large. Or rarely. With accompanying crash and surge in forest animal populations. Unstable.

Wildlife populations are a chaotic system, neither cyclical nor stable.

Much like the weather.

That's just because we see that now, after destabilization by human activity? Remember the giant sequoias - they lasted 5000 years.

As demonstrated by the logistic map[1][2]

[1]: https://en.wikipedia.org/wiki/Logistic_map

[2]: https://www.youtube.com/watch?v=ovJcsL7vyrk

Storms do not easily flatten small trees, small trees are usually the most resistant to wind.

This is just a loggers point of view and too much simplified. Ecology uses more than one variable.

> A strong storm could flatten the entire grove.

I can't see why. Those are life beings, not dominoes

I could see all that, but is it “unhealthy”?

That seems like a subjective human label. If a lightening strike burns down a forest and it starts to regrow, is that forest now “unhealthy”?

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