5 ms·

I find this stuff absolutely incredible. I’ve been learning recently about this phenomenon being known, but not understood. The most obvious indication was th

I find this stuff absolutely incredible. I’ve been learning recently about this phenomenon being known, but not understood. The most obvious indication was that logging leads to less rain, so it seems as though trees actually cause rain. One theory was that turbulence in the air above forests could trigger precipitation, and while that might still be a factor, this explanation is very clean and easy to understand. This is awesome in any case. I’ve been wanting to use the “trees cause rain” point in discussions about forestry and hydrology, but had to be careful because we only had correlations as far as I knew. This doesn’t fully solve that, but certainly helps explain and create a causative link. Also just incredible how evolution works. Of course trees cause rain, haha. I wonder if other plants such as grasses in vast plains have their own tricks to seed rain, or if their strategy is surviving drought extremely well. It’s all cool either way.

xctr94 3y ago
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.
- philipov 3y ago
  Are you telling me the Rain Follows The Plow folks were actually on to something?
  - mooreds 3y ago
    Solid joke :) . Unfortunately, you typically don't plant trees with a plow.
    - the_third_wave 3y ago
      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 https://core.ac.uk/download/pdf/228205053.pdf
- brnaftr361 3y ago
  I bet there's folk tales that parallel it with angry forest spirits, too. Explaining the unknown with anthropomorphization.
- Avshalom 3y ago
  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.
- steve_adams_86 3y ago
  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.
- dr_dshiv 3y ago
  Terpenes from trees also produce OH which converts methane to CO2. No idea whether this has a big effect, but I find it fascinating.
- aeroman 3y ago
  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-4-677-2011.pdf https://gmd.copernicus.org/articles/4/677/2011/gmd-4-677-201... [1] - https://www.nature.com/articles/nature12674 https://www.nature.com/articles/nature12674
- Loughla 3y ago
  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.
  - steve_adams_86 3y ago
    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.
    - Loughla 3y ago
      Yes, but that is a different problem than immediate water availability for crop use.
      - xctr94 3y ago
        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.
        Loughla 3y ago
        > 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?
    - lrem 3y ago
      It's almost as if farmers were inclined to borrow water from their descendants some centuries down the line, isn't it?
- agumonkey 3y ago
  If you have a reading list to suggest, i'm all ears.
  - xctr94 3y ago
    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.
StewedHarry 3y ago
You should read the extended phenotype by Richard Dawkins if you haven't already
giraffe_lady 3y ago
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.
meristohm 3y ago
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.
- jazzyjackson 3y ago
  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
  - Avshalom 3y ago
    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).
    - sampo 3y ago
      In infrared, green leaves are more reflective than bare soil or concrete.
    - nostromo 3y ago
      Trees also act as thermal sinks. They transfer surface heat down into their roots, where it is cool underground.
      - eep_social 3y ago
        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.
imjonse 3y ago
They aren't called rainforests for no reason :)
- magneticnorth 3y ago
  I had always assumed that causality ran the complete other direction! Rain -> happy plants -> big trees draped in ferns and vines and mosses.
jazzyjackson 3y ago
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
- steve_adams_86 3y ago
  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.
  - runsWphotons 3y ago
    If you graze animals the right way you can also increase biomass/help the ecosystem.
lukas099 3y ago
Re: grasses surviving drought, I believe they do this by having extremely deep roots (likely among many other adaptations).
sorokod 3y ago
Matches what Richard Dawkins calls "the extended phenotype" From wikipedia ( https://en.wikipedia.org/wiki/The_Extended_Phenotype 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."
mlinhares 3y ago
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.
Beijinger 3y ago
[flagged]
aaron695 3y ago
[dead]
dclowd9901 3y ago
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)?
pvaldes 3y ago
Grasses (Poaceae) catch dew easily and move it towards its center. Most plants sometimes release water drops also (see guttation)
hammock 3y ago
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
InSteady 3y ago
>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.
Solvency 3y ago
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?

xctr94 3y ago

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.

philipov 3y ago
Are you telling me the Rain Follows The Plow folks were actually on to something?
- mooreds 3y ago
  Solid joke :) . Unfortunately, you typically don't plant trees with a plow.
  - the_third_wave 3y ago
    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 https://core.ac.uk/download/pdf/228205053.pdf
brnaftr361 3y ago
I bet there's folk tales that parallel it with angry forest spirits, too. Explaining the unknown with anthropomorphization.
Avshalom 3y ago
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.
steve_adams_86 3y ago
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.
dr_dshiv 3y ago
Terpenes from trees also produce OH which converts methane to CO2. No idea whether this has a big effect, but I find it fascinating.
aeroman 3y ago
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-4-677-2011.pdf https://gmd.copernicus.org/articles/4/677/2011/gmd-4-677-201... [1] - https://www.nature.com/articles/nature12674 https://www.nature.com/articles/nature12674
Loughla 3y ago
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.
- steve_adams_86 3y ago
  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.
  - Loughla 3y ago
    Yes, but that is a different problem than immediate water availability for crop use.
    - xctr94 3y ago
      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.
      - Loughla 3y ago
        > 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?
  - lrem 3y ago
    It's almost as if farmers were inclined to borrow water from their descendants some centuries down the line, isn't it?
agumonkey 3y ago
If you have a reading list to suggest, i'm all ears.
- xctr94 3y ago
  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.

StewedHarry 3y ago

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

giraffe_lady 3y ago

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.

meristohm 3y ago

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.

jazzyjackson 3y ago
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
- Avshalom 3y ago
  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).
  - sampo 3y ago
    In infrared, green leaves are more reflective than bare soil or concrete.
  - nostromo 3y ago
    Trees also act as thermal sinks. They transfer surface heat down into their roots, where it is cool underground.
    - eep_social 3y ago
      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.

imjonse 3y ago

They aren't called rainforests for no reason :)

magneticnorth 3y ago
I had always assumed that causality ran the complete other direction! Rain -> happy plants -> big trees draped in ferns and vines and mosses.

jazzyjackson 3y ago

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

steve_adams_86 3y ago
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.
- runsWphotons 3y ago
  If you graze animals the right way you can also increase biomass/help the ecosystem.

lukas099 3y ago

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

sorokod 3y ago

Matches what Richard Dawkins calls "the extended phenotype" From wikipedia ( https://en.wikipedia.org/wiki/The_Extended_Phenotype 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."

mlinhares 3y ago

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.

Beijinger 3y ago

[flagged]

aaron695 3y ago

[dead]

dclowd9901 3y ago

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)?

pvaldes 3y ago

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

hammock 3y ago

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

InSteady 3y ago

>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.

Solvency 3y ago

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?