There is a place in So Cal now called The Aspens South Coast we lived in 30 years ago. It has (had?) an incredibly dense concentration of trees, something I’ve not seen since in that region, which is of course desert.
This time of year when you opened the gate that separated the treed interior from the parking lot you felt like the air conditioning had been turned on. We have very fond memories of the place. Its only disadvantage for me was that spring caused my allergies to go crazy.
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.
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.
>> 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.
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.
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.
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
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?
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.
Trees acts for their little thermal mass and large surface exposed to air, essentially IR radiation from the Sun can't much reach the ground or humans under trees (if they are large and dense enough) and the part of the radiation touching trees get quickly dispersed in the air (climbing the atmosphere).
The limited effect is that cities are dense and can't be made as forest so trees can't do nothing for buildings taller them them.
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.
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"
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...
> 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.
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)
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.
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.
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.
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.
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 ...
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?)
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.
MIT should deploy their desert water tech in LV[0]
Since the point of the trees has been discovered to be just shade and not evaporative cooling, they just need to figure a way to reorient their panels?
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.
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.
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.
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.
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
I hope there would be enforced regulation around this kind of thing in cities in India. In residential areas, it's common that your house takes up almost all of your available plot space, and on top of that mostly constructed from concrete.
Air temperature is already high (e.g. 36C at my location just now), and radiant heat from sun and concrete can make the felt temperature more like 60C.
It's sad that new real-estate layouts continue to be approved, which will only be good for this type of dense concrete hell.
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.
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.
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.
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)
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.
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")
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.
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.
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.
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.
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.
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.