Genuine question for people in the field. My understanding is that the cooling effect of trees is primarily driven by evaporative cooling. That is, the shade effect only really exists because the plant does not shrivel up and die due to storing water. How much more effective are trees vs. big swamp coolers? Even in this article, they admit that daytime cooling of half a degree requires 3 times more water.
zamadatix · 2h ago
There is something to be said for the parts about shading the surface too though. You're unlikely to cool an entire desert a significant amount with water you bring in but if that's something that happens as part of keeping the actual surfaces in the city cooler during peak heat times on top of the air cooling effects of evaporation then the sum result is greater than the parts in terms of effect.
Of course it's Vegas, I wouldn't be surprised if we decided to make the downtown completely indoors so we could just run AC in the streets too. It's not exactly the city of practicality.
sandworm101 · 3m ago
>> the downtown completely indoors so we could just run AC in the streets too.
So ... a shopping mall? Many cities do this already, linking various public indoor spaces by walkways/tunnels. Also those cities where the air outside is too cold. A few canadian universities link buildings with tunnels so students can avoid going outside.
trhway · 31m ago
They do outdoor AC in [some places in some] parks in Qatar.
firesteelrain · 11m ago
Sounds like Qatar. Innovative and expensive.
chrisweekly · 9m ago
Under the sand on the beach, too!
obblekk · 1h ago
In the abstract it discusses that most of the effect (16deg Celsius) is from reduced radiative heating and only a few degrees from evaporation.
Mostly the benefit is instead of having the concrete under you absorb and emit the sun, the leaves above you do.
This dramatically reduces the heat we feel at human height.
wyldfire · 31m ago
> the effect (16deg Celsius)
Did I read that right? 16°C seems like an enormous effect.
Seems like trees would be a small investment to effectively get "outdoor AC-ish"?
No comments yet
trhway · 29m ago
Even without any evaporative effect, the air cooling of leaves (at least bringing them to the surrounding air temperature) happens more easily than that of concrete pavement due to height and larger surface area. The concrete can easily get heated much hotter than the air at even 10-20ft.
Wrt. water consumption - Mediterranean species like say olive trees are kind of optimized for low water consumption, by for example having leaves covered with wax-like stuff decreasing evaporation.
PaulHoule · 1h ago
The point of that article is that in many places the evaporative cooling is the main thing but in Vegas the water situation is such that it's more about the shade so the optimal tree is something that gives shade but doesn't need a lot of water.
Right where I am sitting now I have an LED strip above my desk and when I have my shirt off (right now) I can very definitely feel the radiant energy when it is on, so if it is really hot I either turn it off or switch it to green because the eye is most sensitive to green light. In fact, as I'm writing this, I just set the backlight on the 55-inch TV I use as a computer monitor down so I'd feel more comfortable.
sidewndr46 · 26m ago
So an umbrella?
PaulHoule · 14m ago
Yeah, but like an umbrella made by something like Drexler's nanotechology.
cryzinger · 1h ago
The increased water usage is tough because we're serious about water reclamation here in Vegas, but you can't reclaim water lost to evaporation, which is why there are policies (and serious fines) around excessive landscape watering. It might not be a worthwhile tradeoff, especially if there are alternate cooling methods that don't involve water loss.
photonthug · 1h ago
Trees are great, but ultimately a pretty ridiculous idea if the goal is to create shade, even if you're not worried about water consumption. Avoiding concrete walls or overhangs is smart because you don't want the thermal mass.. but of course you can build these things out of fabric or thin metal.
The funny thing is, if you build a wall or canopy to avoid the water consumption plus literally waiting a decade for a tree to get tall.. now you're probably in violation of your HOA height restrictions, etc. Desert cities need to basically drop the idea of conforming to the typical expectations of visitors and newcomers by trying to add greenery. It's better to add shade, dig underground, build wind-catchers[1], salsabils[2]. There's tons of basic things like making sure roof surfaces are more reflective, and more strategic architectural things[3] that can be done to improve things and the techniques have been used forever
Trees are also vertical structures. Any vertical structure will absorb some of the light, turning it into heat, then be cooled by rising air. This keeps the heat from getting to the ground, with or without evaporation. In other words, instead of the sidewalk getting hot, something 20+ feet in the air get hot. Hot air rises and the air near the ground stays cooler.
idbehold · 2h ago
Swamp coolers can't generally provide shade.
jetru · 2h ago
I got a great business idea now.
metalman · 39m ago
part of the cooling effect that trees produce is from photosynthesis, the percentage of light converted to plant matter can be as high as 1.5%
more will be reflected, and the shaded area will of course,be shaded, and then there is transpiration of water, which varys greatly with species.other effects will be due to the built environment, where a lot of asphalt and concrete could mostly obliterate the real effects of a few trees.
from wiki "The average rate of energy captured by global photosynthesis is approximately 130 terawatts, which is about eight times the total power consumption of human civilization"
There is literally no difference. Water is water, and its specific heat of evaporation doesn't depend on the way it's evaporated.
b00ty4breakfast · 3h ago
I'm sure any future endeavor to plant trees in the goddamn desert will have no negative environmental consequences at all. It's not as if the city in the goddamn desert is already in the middle of a regional water crisis as of last year or anything...
Street trees are hugely beneficial and if you want to cut something (ha ha), you want to look at things like lawns or golf courses.
tshaddox · 1h ago
> In 2014, Southern Nevada’s gross water demand was about 205 gallons per capita per day (GPCD). In the region, single- and multi-family households account for 60 percent of water consumption—70 percent of which is used for landscaping.
In New Mexico and Arizona, 7% of water is for residential use, another 7% is for retail, commercial and power generation. 75% goes to agriculture.
Trees in cities are not about reducing water usage by any significant amount. They are still lovely, though.
whartung · 2h ago
Having lived in the desert, and not talking Vegas, but Nevada desert where folks bought cheap lots, dragged a single or double wide trailer into it, and started a life.
Trees were the first thing planted. Fast growing trees, placed to cast shade on the house.
After a few years, those dirt lots transformed into some very nice properties where sitting outside in the shade with the desert zephyrs rustling the leaves provide a very nice, idyllic place for conservation or reading.
ethagnawl · 1h ago
There are a few of these plots outside of Crestone, CO that I've always dreamed of visiting. They truly look like oases and it must be surreal to sit in the shade and read while looking out onto the surrounding desert.
jameslk · 1h ago
Southern Nevada uses a tiny amount of water compared to most states, about 2% of the total that’s apportioned from the CO river, and recycles about 40% of it. For indoor usage, 99% of water is recycled.
I agree growing things in the desert may be inefficient, but speaking for the CO river, that problem is in California and Arizona.
> [Las Vegas] used 38 billion gallons less water in 2024 than in 2002, despite a population increase of approximately 829,000 residents during that time. This represents a 55 percent decline in the community’s per capita water use since 2002.
The earliest human civilizations where all located in deserts. It is not a foreign thing to our species at all.
However, large scale commercial agriculture in desert areas without significant ground water - that's a new thing, and it's a problem.
No comments yet
photonthug · 2h ago
Yes, because living in the desert is absurd and obviously unnatural. Setting aside of course 3,000 years of civilization in Egypt. While we're at it, let's also unpack all these skyscrapers in New York and Tokyo and make sure no one is living at any height greater than the monkeys in the trees.
lazyasciiart · 1h ago
The Nile is, uh, enormously relevant to Egyptian civilization.
photonthug · 1h ago
Wait until you hear about the mighty Colorado. The Hoover dam wasn't just built to imprison Decepticons you know
RhysU · 13m ago
What about the Decepticons he or she has yet to meet?
Analemma_ · 53m ago
I think doing agriculture in a desert is more ridiculous than living there, but the Central Valley exists all the same.
readthenotes1 · 2h ago
It's not an either or type situation
AnimalMuppet · 2h ago
No, but it is an 80-20 type situation. 80% of the water use is agricultural.
agumonkey · 2h ago
There may be counter intuitive effects in there. Plants roots creates water buffer zone underground that can capture some of rainfall and make better use of it, allowing larger growth.
gerdesj · 2h ago
Perhaps the desert will repent its desertness and accept that sand, minimal water and a massive diurnal temperature range will somehow become amical towards good old Plane trees.
OK, let's go full mad world: a vast web of PV for power. Is there a handy massive water resource deep underground? If not then moisture in the air will need redeploying. Tall towers and probably gobs of power are indicated for that.
AlotOfReading · 2h ago
Trees grow in the desert. Mesquites, pines, junipers and more are all widespread in areas around Vegas. You don't need a tropical paradise to have vegetation, as the native forests of Arizona and Utah show.
PaulDavisThe1st · 2h ago
> Is there a handy massive water resource deep underground
There was.
We've been sucking them dry for a century or more, everywhere they exist.
ASalazarMX · 2h ago
There are proven methods for growing plants and trees in arid regions [0], but they have disadvantages which will become more evident as desertification expands with global warming. I agree that forcing non-native trees there is a losing battle in the long run.
If people were really serious about living in deserts in a sustainable way, they can't expect to have decorative greenery or classic architecture. A society as advanced as ours should be able to make compromises that allow modern comforts while adapting so well to their environment that the cities would look almost alien.
Not alien. Arabic, Spanish, mid-mediterranean, Puebloan, and a few more.
The architecture has existed for centuries, maybe even millenia. Some of us already live that way.
The irony is that the key thing - large thermal mass - has now become the province of only those with lots of money, or those with no money. Everyone in the middle is stuck with silly construction options for a desert climate.
asmor · 2h ago
That captcha sure reduces the effectiveness of me reading that by 100%.
any group strategy to push back against the overuse of whole-page captchas ?
Do we all need to run an AI browser plugin now that auto-fills cloudflare captchas ?
EGreg · 1h ago
Is it just me, or has anyone also noticed that trees in southern climates closer to the equator (not jungles) have very few leaves and shade as opposed to trees in climates away from the equator (not tundras)?
What happens if you import northern US trees, the ones that produce a lot of shade, into southern states? Has this been tried?
It is also why there is very little shade in, say, Florida. Only occasional parts of the Martin Grade “scenic” highway look like a regular scene in the north.
matthewfcarlson · 3h ago
Surprise surprise, vegetation is way better than concrete when it comes to being comfortable in a city
pvorb · 3h ago
Not building your city in the desert is also a good idea when it comes to being a comfortable city.
davidw · 2h ago
It costs less to cool than to heat, by and large. And deserts have a lot of sunshine that can be converted into electricity for cooling...
pvorb · 2h ago
But lack of water will become a huge problem when your city is growing that fast in a heating climate.
Edit: And cooling only works inside buildings or cars. Part of a comfortable city is being able to go outside and have a social life outside of a casino.
margalabargala · 2h ago
Municipal uses like drinking, showering, and watering ornamental plants is a tiny pct of desert water use. Most of it is crop irrigation, because if you can will water into existence then crops grow great in sunny deserts.
If the US' alfalfa exports to Saudi Arabia went down by 10%, we would never have a municipal water shortage in the American West in the next century.
SpicyUme · 2h ago
There are people pushing for more shade in cities as an adaptation for a warming world. There is some crossover with the push for a reduction in cars and generally reducing the footprint of streets. Looking at old cities in hot climates I can see how this could make sense.
For Las Vegas, Cottonwoods are native and grow pretty quickly. Like many poplars they were used to grow shelterbelts.
Dig1t · 1h ago
Lack of water is a political problem. We have vast oceans which can be desalinated. Israel gets 85% of its water from desalination, they have gone from water shortages to having a water surplus.
We pump oil via pipelines vast distances, we can do the same with water.
We have virtually unlimited energy locked in Uranium which could power desalination plants, or heck you could power them with solar.
There’s plenty of water for the whole planet. There’s also plenty of clean energy (see nuclear and solar point earlier). But tapping these resources requires a functional government or at least a bureaucracy willing to allow companies to build.
AnimalMuppet · 2h ago
I don't think anybody ever moved to Vegas expecting to be able to have a street life.
helpfulclippy · 2h ago
I used to hang out with my friends and neighbors outside all the time in Las Vegas.
...just not so much in May-August.
No comments yet
toast0 · 1h ago
That's a great idea, but hard for the city of Las Vegas to implement. Clark County doesn't have any ability to build a city not in a desert either. The state of Nevada doesn't have much of anywhere to put a non-desert city either.
Very few municipalities are willing to deny new residents, either. It wouldn't be anywhere on my list of viable places to live, but population growth in the Las Vegas metro area has been consistently large since 1910 until recently (only 10% growth from 2010 to 2020). The municipalities should likely invest in livability and comfort where possible.
gerdesj · 2h ago
I've just been presented with a captcha thingie asking me to select all things that can be picked up by a pair of chopsticks described as "the tool in the image"
Fuck off.
Then that vanished and another even more vapid effort appeared.
Fuck off.
If you need to piss around with this sort of nonsense, you probably shouldn't be entrusted with a website.
out-of-ideas · 1h ago
i clicked the url and saw that first very weird looking captcha - then immediately closed the tab
looks like the archivers have trouble with it too; reminds me of the behavior of a virus with all the redirects lol
Looping redirects on archive.XX urls often traces back to the use of Cloudflare DNS resolver .. the archive folk have some beef with Cloudflare over (?) handling privacy (?) and loop redirects on connections that arrive via that path.
It's a new captcha type for myself also. Interesting as it requires spatial reasoning and a bridge of understanding between text request and objects in images - although it falls to the usual farm of human captcha solvers.
out-of-ideas · 1h ago
nice, well i am using quad9; archive.org had 503's too (edit: lol i wonder if it did complete for me but somehow something else caused a loop - i never went to the search prompt afterward)
Of course it's Vegas, I wouldn't be surprised if we decided to make the downtown completely indoors so we could just run AC in the streets too. It's not exactly the city of practicality.
So ... a shopping mall? Many cities do this already, linking various public indoor spaces by walkways/tunnels. Also those cities where the air outside is too cold. A few canadian universities link buildings with tunnels so students can avoid going outside.
Mostly the benefit is instead of having the concrete under you absorb and emit the sun, the leaves above you do.
This dramatically reduces the heat we feel at human height.
Did I read that right? 16°C seems like an enormous effect.
Seems like trees would be a small investment to effectively get "outdoor AC-ish"?
No comments yet
Wrt. water consumption - Mediterranean species like say olive trees are kind of optimized for low water consumption, by for example having leaves covered with wax-like stuff decreasing evaporation.
Right where I am sitting now I have an LED strip above my desk and when I have my shirt off (right now) I can very definitely feel the radiant energy when it is on, so if it is really hot I either turn it off or switch it to green because the eye is most sensitive to green light. In fact, as I'm writing this, I just set the backlight on the 55-inch TV I use as a computer monitor down so I'd feel more comfortable.
The funny thing is, if you build a wall or canopy to avoid the water consumption plus literally waiting a decade for a tree to get tall.. now you're probably in violation of your HOA height restrictions, etc. Desert cities need to basically drop the idea of conforming to the typical expectations of visitors and newcomers by trying to add greenery. It's better to add shade, dig underground, build wind-catchers[1], salsabils[2]. There's tons of basic things like making sure roof surfaces are more reflective, and more strategic architectural things[3] that can be done to improve things and the techniques have been used forever
[1] https://en.wikipedia.org/wiki/Windcatcher [2] https://en.wikipedia.org/wiki/Salsabil_(fountain) [3] https://en.wikipedia.org/wiki/Passive_cooling
https://en.wikipedia.org/wiki/Photosynthesis
https://www.knpr.org/show/knprs-state-of-nevada/2024-08-29/w...
For instance where I live east of the Cascades, in the dry part of Oregon, only like 10% of the water used goes to the cities.
https://www.centraloregonlandwatch.org/update/2021/5/5/droug...
Street trees are hugely beneficial and if you want to cut something (ha ha), you want to look at things like lawns or golf courses.
I found this quote in this 2016 PDF from the EPA:
https://www.epa.gov/sites/default/files/2017-02/documents/ws...
Trees in cities are not about reducing water usage by any significant amount. They are still lovely, though.
Trees were the first thing planted. Fast growing trees, placed to cast shade on the house.
After a few years, those dirt lots transformed into some very nice properties where sitting outside in the shade with the desert zephyrs rustling the leaves provide a very nice, idyllic place for conservation or reading.
I agree growing things in the desert may be inefficient, but speaking for the CO river, that problem is in California and Arizona.
https://www.snwa.com/water-resources/where-water-comes-from/...
https://lvgea.org/water/
https://www.cleanwaterteam.com/about-us/who-we-are
> [Las Vegas] used 38 billion gallons less water in 2024 than in 2002, despite a population increase of approximately 829,000 residents during that time. This represents a 55 percent decline in the community’s per capita water use since 2002.
https://www.lvvwd.com/conservation/measures/index.html
However, large scale commercial agriculture in desert areas without significant ground water - that's a new thing, and it's a problem.
No comments yet
OK, let's go full mad world: a vast web of PV for power. Is there a handy massive water resource deep underground? If not then moisture in the air will need redeploying. Tall towers and probably gobs of power are indicated for that.
There was.
We've been sucking them dry for a century or more, everywhere they exist.
If people were really serious about living in deserts in a sustainable way, they can't expect to have decorative greenery or classic architecture. A society as advanced as ours should be able to make compromises that allow modern comforts while adapting so well to their environment that the cities would look almost alien.
0. https://en.wikipedia.org/wiki/Desert_greening
The architecture has existed for centuries, maybe even millenia. Some of us already live that way.
The irony is that the key thing - large thermal mass - has now become the province of only those with lots of money, or those with no money. Everyone in the middle is stuck with silly construction options for a desert climate.
Las Vegas is embracing a simple climate solution: More trees (npr.org) 21 days ago | 143 comments https://news.ycombinator.com/item?id=44231151
Nights in Las Vegas Are Becoming Dangerously Hot (nytimes.com) 10 months ago | 1 comment https://news.ycombinator.com/item?id=41223831
Do we all need to run an AI browser plugin now that auto-fills cloudflare captchas ?
What happens if you import northern US trees, the ones that produce a lot of shade, into southern states? Has this been tried?
It is also why there is very little shade in, say, Florida. Only occasional parts of the Martin Grade “scenic” highway look like a regular scene in the north.
Edit: And cooling only works inside buildings or cars. Part of a comfortable city is being able to go outside and have a social life outside of a casino.
If the US' alfalfa exports to Saudi Arabia went down by 10%, we would never have a municipal water shortage in the American West in the next century.
For Las Vegas, Cottonwoods are native and grow pretty quickly. Like many poplars they were used to grow shelterbelts.
We pump oil via pipelines vast distances, we can do the same with water.
We have virtually unlimited energy locked in Uranium which could power desalination plants, or heck you could power them with solar.
There’s plenty of water for the whole planet. There’s also plenty of clean energy (see nuclear and solar point earlier). But tapping these resources requires a functional government or at least a bureaucracy willing to allow companies to build.
...just not so much in May-August.
No comments yet
Very few municipalities are willing to deny new residents, either. It wouldn't be anywhere on my list of viable places to live, but population growth in the Las Vegas metro area has been consistently large since 1910 until recently (only 10% growth from 2010 to 2020). The municipalities should likely invest in livability and comfort where possible.
Fuck off.
Then that vanished and another even more vapid effort appeared.
Fuck off.
If you need to piss around with this sort of nonsense, you probably shouldn't be entrusted with a website.
looks like the archivers have trouble with it too; reminds me of the behavior of a virus with all the redirects lol
edit: for those with custom filterlists via ubo:
- ||iop.org
There's also a direct PDF link https://iopscience.iop.org/article/10.1088/2752-5295/ade17d/... that also prompts for captcha (unless you arrive there via the web version)
Looping redirects on archive.XX urls often traces back to the use of Cloudflare DNS resolver .. the archive folk have some beef with Cloudflare over (?) handling privacy (?) and loop redirects on connections that arrive via that path.
It's a new captcha type for myself also. Interesting as it requires spatial reasoning and a bridge of understanding between text request and objects in images - although it falls to the usual farm of human captcha solvers.