Hacker News Reader

I’ve been reading agroforestry and permaculture books for a while — I’d love to get into farming —, and this has been known for ages.

Even if not fully understood, it’s well known in agro that trees raise the humidity level of an area and create micro-climates that increase the amount of rain (e.g. of doing nut trees in a valley).

I think… modern agriculture just forgot/ignores ancient knowledge.

Are you telling me the Rain Follows The Plow folks were actually on to something?

Solid joke :) .

Unfortunately, you typically don't plant trees with a plow.

Actually you do, at least when planting on a large scale. A planting plough is pulled behind a tractor, the device opens a furrow into which seedlings are dropped at a regular interval by someone riding the plough or mechanically. The furrow is closed with the top of the seedling sticking out.

Here's how you can convert an old plough to a tree planting plough:

https://core.ac.uk/download/pdf/228205053.pdf

I bet there's folk tales that parallel it with angry forest spirits, too. Explaining the unknown with anthropomorphization.

local humidity levels is just transpiration, which yeah in a valley trapping the humidity can create rain but that's not the same as this cloud seeding mechanism.

Without a doubt, and it’s well known in urban planning and landscaping too. But in a discussion about why industry might be harmful, not having facts to back yourself up makes your case effectively irrelevant. Even pointing to countless reforestation projects with heaps of positive precipitation and hydrological data is no help; as long as the mechanism isn’t clear, people who want to maintain business as usual will not listen.

So, information like this is a huge help and a step towards having a more crystallized picture of why forests are crucial to hydrology.

Terpenes from trees also produce OH which converts methane to CO2. No idea whether this has a big effect, but I find it fascinating.

The increase in humidity is actually a different effect - evapotranspiration from trees is included in climate models (along with their response to increasing CO2 concentrations) [0].

The effect in this article is more to do with the particulates that form from the chemical emitted from trees. The article doesn't make it clear, but an increase in tree particulates (known as aerosols) would actually cause less rain.

Almost all cloud droplets form on an aerosol particle, so the cloud droplets in a cloud with more aerosols are on average smaller (as the water is spread out over more droplets). These smaller droplets take longer to grow large enough to form rain, an effect which is thought to decrease the amount of precipitation in some regions (although by a small amount).

This effect is also included in climate models, but the sources of aerosol (such as from trees) are more uncertain [1], producing the uncertainty in future climate projections.

[0] - https://gmd.copernicus.org/articles/4/677/2011/gmd-4-677-201...

[1] - https://www.nature.com/articles/nature12674

Modern agriculture didn't forget. It chose differently because quantity is the only measure of success. Trees causing rain has to be substantially less efficient in the short term than irrigation.

The trouble is that reduced forest leads to reduced rain, and irrigation often reduces ground water which is replenished even slower than before. It accelerates water losses a lot faster than anyone expected.

Yes, but that is a different problem than immediate water availability for crop use.

I agree that irrigation needs are urgent. However, we also need incentives towards an eventual transition.

A basic example: contours to mitigate how fast water moves in elevated terrain. Cheap and effective. Then water collected at dug basins in the bottom.

If you have cheap, constant access to water, you irrigate industrially. It’s only when droughts, lack of groundwater, climate effects, etc. kick in that the alternatives become important. But by then, you didn’t put them in place early enough.

So I think farming deserves both short- and long-term thinking. Business as usual won’t work as climate conditions get worse.

> basic example: contours to mitigate how fast water moves in elevated terrain. Cheap and effective. Then water collected at dug basins in the bottom.

Before I respond, I have another question: Are you saying this is something we are not doing and should be?

It's almost as if farmers were inclined to borrow water from their descendants some centuries down the line, isn't it?

If you have a reading list to suggest, i'm all ears.

I’ve lots on my e-reader, but I keep going back to Ben Falk. “The Resilient Farm and Homestead” is super cool, you actually follow their story over multiple years, with the farm’s changes rather well documented! Of course the more scientific books on the topic are better information-wise — some used at uni —, but Falk’s is nice to read.

Trees are a collection of straws into the ground, sucking up water with negative pressure due to evaporation through the leaves. It's cool that there are cloud-seeding chemicals released as well.

Forests smell and feel much better that clear-cut spaces, I know that much. I'd rather the USDA and Forest Service adopt more-sustainable logging practices, for leased land especially (where the economics equation currently favors clear-cutting), like the Menominee in northern Wisconsin.

i've also wondered how much energy is absorbed by trees, I know on a 100 degree day the coolness of a shady grove well outcompetes the shade of a simple picnic shelter

there's a couple things going on there. Photsynthesis isn't absorbing much its ~1-2% efficiency (so mostly just waste heat) but plants are mostly water which has a high heat capacity so it warms slower than a kiln dried wood structure. Wood/bark is also way less reflective than concrete and (living) plants respond to heat by opening up pores and letting water evaporate out of them (basically sweating) which can lower the dry bulb temperature (especially if there's any breeze).

In infrared, green leaves are more reflective than bare soil or concrete.

Trees also act as thermal sinks. They transfer surface heat down into their roots, where it is cool underground.

More precisely, the temperature underground is very stable. At 8-12 feet there is little to no variation over the course of a year. So in a cold season it will be warmer underground than ambient (this is why foundations are dug “below the frost line”) while the opposite is true during a warm season.

Would evaporative cooling due to transpiration have a significant impact?

trees basically perform cloud-seeding by releasing micro-droplets of oils into the air

"climate: a new story" by charles eisenstein is a great resource on an alternative understanding to climate change then simply "CO2 bad", which he presents as a red herring to ecosystem destruction

conventional wisdom is apparently "fair weather leads to more biomass" when the reality might be "more biomass leads to fair weather" as every ecosystem acts as a chemical and energetic buffer

This is really interesting to consider, and I hadn’t before. It lends a lot more potential weight and credibility to the idea that rewilding plains (for example), thus increasing the biomass there, would have significant climate benefits. This falls deep into the “We can’t know that” category, but I’m a fairly large proponent of leaving more land alone and letting nature do what it does. At the moment, economic activity like grazing cows seems like it could be a net negative since it’s clearly harming the environment while also preventing natural landscapes from establishing, which could have significant ecological benefits.

The idea that biomass can bring stability and better conditions is certainly supported by my aquarium experience, though it’s a closed system. If you limit the number of species, water parameters will swing all over the place. Add more species (particularly plants and micro flora/fauna), and the water becomes clearer and cleaner. Add some small crustaceans, snails, or other animals which love algae and it’ll get even cleaner, and their populations will self-maintain quite well. Add some tiny fish and they will live on the algae, micro fauna, offspring of the shrimp, etc. These systems work well, but they need a huge amount of plants and tiny creatures, bacteria, and small animals to groom and maintain things. Without them, it’ll crash and swing all over until just about everything is dead.

If we imagine the world as a giant aquarium where we inhibit the micro flora and micro fauna, bacteria, and other balances, it certainly seems possible that restoring this would improve all kinds of factors like water and air quality.

If you graze animals the right way you can also increase biomass/help the ecosystem.

Not really true.

https://newrepublic.com/article/163735/myth-regenerative-ran...

https://grist.org/climate-energy/cattle-grazing-is-a-climate...

https://www.nature.com/articles/nature25138

https://www.oxfordmartin.ox.ac.uk/publications/grazed-and-co...

https://plantbasednews.org/news/environment/george-monbiot-r...

“So any story that says it’s good to be farming these livestock, it’s good to be eating these livestock, is a story which justifies among the most devastating processes on Earth,” he said. “It is climate science denial.”

Monbiot linked this denial to the interests of major corporations like McDonald’s, General Mills, JBS, and the Murdoch Network, who he says have “backed and weaponized” the idea that grazing cattle is environmentally beneficial. “The story is false,” he said. “When you make a grand claim such as this one, that livestock can mitigate climate change, either you produce the evidence for that claim or if you cannot produce the evidence you withdraw the claim. The evidence has not been produced, the claim does not stand.”

For what it’s worth, there are other studies indicating this as well. There isn’t good data suggesting we can graze animals on a large scale and increase biomass in a meaningful way compared to other options. The trouble is that other options inevitably include “stop eating meat”, and people don’t like to hear this.

That’s a big if. The vast majority of animals raised in North America aren’t grazed sustainably, especially if you exclude Canada. It’s kind of like saying you can drive without emissions when 99% of the world is driving gas cars, only in this case, there’s no trend towards grazing sustainably and no reason to believe it will start happening (whereas vehicles likely will continue trending towards electric motors). I just can’t think of a better analogy at the moment, but hopefully it makes sense. Proper grazing seems unlikely to ever be adopted on a broad scale, so it’s unlikely to matter that it can be done better.

> aquarium experience

Is this the Walstad Method?

Yes! I love it. Have you given it a shot?

No, I visited a friend of a friend many years ago and learned of it from them. I hope to one day but far too many projects compete for my time.

It’s worth getting to one day! Once you get it started, it’s really not too much work or time, either. But I hear you, too many projects, not much time. It’s a real problem.

Matches what Richard Dawkins calls "the extended phenotype"

From wikipedia ( https://en.wikipedia.org/wiki/The_Extended_Phenotype ):

"Dawkins develops this idea by pointing to the effect that a gene may have on an organism's environment through that organism's behaviour."

They aren't called rainforests for no reason :)

I had always assumed that causality ran the complete other direction! Rain -> happy plants -> big trees draped in ferns and vines and mosses.

Kinda matches the destruction caused by humans beings in the countryside in northeastern Brasil as well. Most of the trees for the somewhat arid climate were felled and droughts that were every 20 years started to become more and more common until now it’s an eternal drought where very little actually grows as it barely rains.

Without exploring the question of why, it makes sense from an evolutionary biology point of view that trees (forests, really, as trees with extensive root systems tend to be pretty drought tolerant) would attract rain. They require it to survive and thrive in the long run

Doesn’t this seem obvious on its face? Any given tree harnesses a tremendous amount of moisture. And it’s constantly “breathing.” Why _wouldn’t_ a preponderance of trees affect ambient moisture (and, by extension, clouds)?

It's fun also because this relationship is explicitly & deeply embedded in some north american indigenous ecologies, maybe others. We've been confidently dismissing it for generations.

I mean is it cool, or incredibly depressing, because the world will march on with its chainsaws obliterating ancient forests in the pursuit of profits?

Grasses (Poaceae) catch dew easily and move it towards its center. Most plants sometimes release water drops also (see guttation)

Re: grasses surviving drought, I believe they do this by having extremely deep roots (likely among many other adaptations).

You should read the extended phenotype by Richard Dawkins if you haven't already

>but had to be careful because we only had correlations as far as I knew

Sooner or later we need to throw caution to the wind when it comes to advocating for behaving more conservatively towards the environment and climate. If we have to wait until we have ironclad proof that we shouldn't be wrecking things, we are A. allowing our caution to be permissive of recklessness, and B. creating a situation similar to the asymmetry of spreading bullshit -- it takes far longer to prove something is harmful than it takes to switch over to some other equally (or more) destructive practice.

Sorry, I'll step off my soapbox now. Not even sure if you were discussing these things in the context of conservation.

It is indeed really cool stuff! The natural world continues to throw surprise after surprise at us, and the more we learn the more it looks like it really is Fern Gully operating in the wilds of our wonderful earth.

Anecdotally, grasses do seem to put off some smell at times, including preceding a heavy rain. To me, they don't seem as as heady and "luscious" like the rich floral terpenes from a forest (then again I'm from the PNW, so I haven't spent as much time in the grasslands). I wonder if it is more soil bacteria that the grasses are in symbiosis with that do the heavy lifting in terms of rain seeding. Neat to wonder about.