hervature 7 hours ago

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 6 hours 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 4 hours 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.

    • sneak 3 hours ago

      If you cover the roof in solar, it will generate more than sufficient power to air condition it.

    • trhway 4 hours ago

      They do outdoor AC in [some places in some] parks in Qatar.

      • firesteelrain 4 hours ago

        Sounds like Qatar. Innovative and expensive.

      • chrisweekly 4 hours ago

        Under the sand on the beach, too!

  • obblekk 5 hours 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 4 hours 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"?

      EDIT: for those of us who are more comfortable with Freedom Units, that's like going from 104°F to 75°F!

    • trhway 4 hours 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.

  • gsf_emergency_2 2 hours ago

    It's confusing phrasing.

    Increasing *evaporative* cooling by 0.5deg requires 3x more water, but shade alone is the *main* mechanism,it doesn't require water.

    >during the day, trees provide significant shade by intercepting solar radiation, reducing mean radiant temperature (up to 16 °C)

  • cryzinger 6 hours 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 5 hours 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

      [1] https://en.wikipedia.org/wiki/Windcatcher [2] https://en.wikipedia.org/wiki/Salsabil_(fountain) [3] https://en.wikipedia.org/wiki/Passive_cooling

      • cryzinger 4 hours ago

        You know how a lot of classic midcentury modern houses (which you can still find in downtown Vegas!) have those kind of lattice-y decorative walls and panels? Are those actually functional for reducing heat and not just cool-looking?

  • PaulHoule 5 hours 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.

  • idbehold 6 hours ago

    Swamp coolers can't generally provide shade.

    • jetru 6 hours ago

      I got a great business idea now.

  • sandworm101 4 hours ago

    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.

  • cyberax 6 hours ago

    There is literally no difference. Water is water, and its specific heat of evaporation doesn't depend on the way it's evaporated.

  • metalman 5 hours 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"

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

b00ty4breakfast 7 hours 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...

https://www.knpr.org/show/knprs-state-of-nevada/2024-08-29/w...

  • davidw 7 hours ago

    Most places in the west, the water used for 'municipal' stuff is a small fraction of the total.

    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.

    • PaulDavisThe1st 6 hours ago

      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.

    • tshaddox 6 hours 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.

      I found this quote in this 2016 PDF from the EPA:

      https://www.epa.gov/sites/default/files/2017-02/documents/ws...

      • mitb6 3 hours ago

        That's because that doc is talking about Southern Nevada (read: Vegas) in isolation, 78% of Nevada water usage is agriculture (followed by 13% residential, 7% mining)

        https://extension.unr.edu/publication.aspx?PubID=4764

        • tshaddox 2 hours ago

          True, and also 75% of Nevada’s population is in the Las Vegas metro area.

          • smus 2 hours ago

            You understand that factoid strengthens the point of the person you're replying to right

  • whartung 7 hours 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 6 hours 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.

  • sorcerer-mar 7 hours ago

    Agriculture is the problem, not urban trees

    • Henchman21 7 hours ago

      Not people attempting to live in a desert?

      • PaulDavisThe1st 6 hours ago

        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.

        • fc417fc802 3 hours ago

          Outside of greenhouses. It's only an issue in an open field. Once properly enclosed the high energy availability is a major upside.

      • photonthug 6 hours 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 6 hours ago

          The Nile is, uh, enormously relevant to Egyptian civilization.

          • photonthug 5 hours ago

            Wait until you hear about the mighty Colorado. The Hoover dam wasn't just built to imprison Decepticons you know

            • RhysU 4 hours ago

              What about the Decepticons he or she has yet to meet?

        • dukeofdoom 3 hours ago

          Egypt went from 8 million to 80 million in the last century. In large part because of the rest of the world (massive grain imports from Ukraine ... for example). But it can obviously work, thanks to globalization and how cheap it's to transport things by container ships.

          Desalination that runs off of Solar panels makes it pretty viable for places like Dubai to exist. The cheap solar energy from the Desert, makes it attractive for future data centers to be placed there. Also, Ancient Egypt had slaves. A lot of the modern middle eastern states rely on cheap labour from India and Afghanistan. And Oil money ...

      • Analemma_ 5 hours ago

        I think doing agriculture in a desert is more ridiculous than living there, but the Central Valley exists all the same.

        • anyonecancode 3 hours ago

          My understanding is that agriculture in the desert works because of all the sunlight, so if water is provided it ends up actually being really good for growing plants.

          (also, I don't think the Central Valley is actually a desert?)

          • dendrite9 4 minutes ago

            Much of it used to be a seasonal wetland/lake until the water was diverted into canals or pumped over the mountains.

          • viccis an hour ago

            >so if water is provided

            ^ the rub ^

            • hollerith a minute ago

              Rivers often run through a desert.

    • readthenotes1 7 hours ago

      It's not an either or type situation

      • AnimalMuppet 6 hours ago

        No, but it is an 80-20 type situation. 80% of the water use is agricultural.

  • agumonkey 6 hours 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 6 hours 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 6 hours 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 6 hours 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 7 hours 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.

    0. https://en.wikipedia.org/wiki/Desert_greening

    • PaulDavisThe1st 6 hours ago

      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.

Raphell 3 hours ago

I don’t think planting trees is only for cooling things down. Sometimes it’s just about helping people feel like they can go outside. In really hot places, even a bit of shade can change your mind about stepping out.

schaefer 2 hours ago

As a matter of local trivia, today (2025.07.01) we had a wind storm in vegas that downed many trees. :)

asmor 7 hours ago

That captcha sure reduces the effectiveness of me reading that by 100%.

6Az4Mj4D 4 hours ago

I saw video last week in India there was similar experiment done in sun the temperature 45 degrees C and 30 step walk under the tree the temperature 36 degrees C. We need more trees as an easy solution

sneak 3 hours ago

The best way to produce shade in the Nevada desert is with solar panels.

The sky is rarely cloudy and solar just blasts all day every day here.

I covered my backyard in Vegas with ground panels and now I charge my EV off of a 100% off grid solar system. The sun provides enough energy in my small yard for 2-3x my driving needs.

gerdesj 6 hours 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 6 hours 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

    edit: for those with custom filterlists via ubo:

    - ||iop.org

    • defrost 6 hours ago

      Archivers work fine for myself: https://archive.md/qUlES

      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.

      • out-of-ideas 5 hours 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)

jgord 5 hours ago

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 5 hours 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.

  • lantry 3 hours ago

    The short answer is, they would die. The trees are the way they are because they've adapted to their environment. At a high level, trees in hot sunny areas will have smaller leaves because they can get enough sunlight from a smaller surface area, and smaller leaves lose less water.

    But it is more complicated than that, of course. It's not just "how hot does it get", but also how much water is available, how windy it is, how cold it gets, and a million other environmental factors. That's why there is such a wide variety among the plants on earth.

    (and yes, it has been tried. Check out the youtube channel "crime pays but botany doesn't")

  • shayway 3 hours ago

    Florida has plenty of shade, though you wouldn't know it considering our city planning. Anything that isn't too dense for humans is pure urban hellscape.

matthewfcarlson 7 hours ago

Surprise surprise, vegetation is way better than concrete when it comes to being comfortable in a city

  • pvorb 7 hours ago

    Not building your city in the desert is also a good idea when it comes to being a comfortable city.

    • davidw 7 hours 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 7 hours 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 6 hours 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 6 hours 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 5 hours 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 6 hours ago

          I don't think anybody ever moved to Vegas expecting to be able to have a street life.

          • helpfulclippy 6 hours 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.

    • toast0 5 hours 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.