Botanical gardens can cool city air by an average of 5°C | Hacker News Reader

Botanical gardens can cool city air by an average of 5°C

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399 pointsBrajeshwar152 comments

I've become really obsessed with 'Miyawaki Forests' lately - small, dense, urban forests which can reach a mature state in only a few years. I hope they start showing up everywhere. Fuck minimum parking requirements, where are the minimum forest requirements?

Incredible - apparently you can do one in your back yard!

https://canadiangeographic.ca/articles/the-many-benefits-of-...

I'm having a hard time picturing what they look like -- and the photo in that article is unrelated.

Googling them, I can find images of a few proof-of-concept plots in the middle of fields but I can't find a single example of how they might integrate with a city.

It would be nice to see some kind of before-and-after, even if just an illustration, to get a sense of how they would fit into a cityscape aesthetically and practically.

Here's a NYT article with some good photos, gift link: https://www.nytimes.com/2023/08/24/climate/tiny-forests-clim...

Here's a photo of what it looks like when it's first planted: https://voice.somervillema.gov/miyawaki-micro-forest

Another good article: https://www.creatingtomorrowsforests.co.uk/blog/the-miyawaki...

PDF with lots of pictures and information: https://urban-forests.com/wp-content/uploads/2020/05/Report-...

They're surely extremely region-specific—sourcing with native trees is a big part of their sustainability. Do you know anything about where to find local growing guides for different regions?

Here's one site that seems solid: https://nativeplantfinder.nwf.org/

Note though that your climate is changing, and what was historically considered native for your region may no longer be a good fit: https://heatmap.news/is-native-gardening-becoming-pointless

I'd love to know if there was an equivalent one for species native to the UK.

EDIT: Found a great list after a little investigation! https://www.north-norfolk.gov.uk/tasks/projects/miyawaki-for...

It doesn't always have to be trees. Hedgerows can be good too.

And a good thing too, because trees in London cause havoc with all the Victorian houses with no foundation in the modern sense.

That 3x3m project shown is not realistic. Not for a newbie and probably not easy to keep from falling apart for an expert.

But yes, wild hedgewoods of a mix of useful shrubs are totally doable even in really small spaces. I had designed a few. They are low maintenance, beautiful, useful, funny, and tasty and everybody should have space for one of this wildlife lifesavers in their gardens.

I bought three boxes of Microforest from Edwina Robinson here in ACT Australia and planted them in my front yard.

Here is an article about her project.

https://www.abc.net.au/news/2021-07-08/act-micro-forests-in-...

It's been two years, the some of the trees are well over 2m tall already.

Possibly a misconception of mine; Australia has some added complexities that not all of us face. What creatures will my mini forest it attract and will my little forest set fire to my home?

I’m in New Zealand where life is less spicey.

You choose what species get planted, so you can control all that. Plant a grove of mainly sheoak for example, and you have fire retardant species that discourage snakes.

Here's video footage of the linked 2021 Canberra plantings from nine months ago - mid 2023.

https://youtu.be/P2_YVkfzpnE?t=23

Accidentally I recently looked up when a bunch of trees are, or can be called a forest. Which I learned is minimal 500 square meters.

How many trees have to be in that region?

It doesn't really mention that. And seems to differ between US and EU already, one source for example, says,

"Forest is a land area of more than 0.5 ha, with a tree canopy cover of more than 10%, which is not primarily under agricultural or other specific non-forest land use."

-- https://agridata.ec.europa.eu/Qlik_Downloads/InfoSheetSector...

There isn't actually a strict definition of what is or isn't a forest

If it’s small area you can’t see a forest, you can see trees.

Well there are definitions, but indeed, not strict, as they do differ quite a bit who or where you ask this question.

From minimum parking requirements to minimum park requirements :-)

Ok maybe minimum forest requirements is more accurate but had to do it

I like the first one, down with minimum parking requirements we want more requirements for minimum parks!

RaRa.

The idea that everything needs to be a dense forest is a problem. What is more helpful is a variety of ecosystems available. I don't have a lot of space, but I managed to have 4 ecosystems in all of my yards with 200+ species of plants: California chaparral, Coastal forest, Xeriscape and a wildflower meadow. Cities could also build such environments and that would be more positive than just planting Miyawaki Forests everywhere.

I can’t imagine these forests will pop up “everywhere”. Seems like a groundless concern.

> I hope they start showing up everywhere.

For people in urban hellscapes? Yes.

For non-human animals? More complicated. These sorts for forests are generally dominated by “edge species”. Edge species generally do relatively well out of habitat fragmentation.

The most sensitive species that need a lot of depth in forest generally don’t do well with these small pockets.

This is not to say that Miyawaki forests aren’t an improvement, just that their “conservation” value is limited and still need to preserve/manage huge amounts of actual contiguous forest with a minimum perimeter compared to the area covered.

That's fair. It's definitely a complementary thing, you want both types of forest I'm sure. Small forests don't cover all the needs, and large forests don't fit everywhere.

I don't disagree but if the choice is between edge forest and species support for species in edge forests, or carparks and species support for carpark friendly species, I would prefer to have edge forest species.

This is not re-wilding. We aren't trying to get urban badgers and lions.

So, in summary I think your critique is true but misplaced. Consider the viable alternatives, not the pipe dream.

When we de-populate on the next virus, we can re-forest for bears.

We actually can affect development patterns, deforestation, and afforestation through democracy.

I am not against Miyawaki forests but I think we need to recognise they are largely for people. They vastly improve important metrics for us but in the press for Miyawaki forests the benefits for forests are sometimes conflated with the benefits of Miyawaki forests.

It’s a little like when growing afforestation for the sake of timber is sold as a benefit to the environment as though it’s just like any other forest.

TFA is about urban overheating. Biodiversity is a powerful idea and valued aesthetic in our society but ultimately biodiversity will only be conserved through a cessation of deforestation and significant afforestation on large scales.

if TFA is about urban overheating, and if Miyawaki forests offset the problem then they should be supported as they address the problem. If they don't help damaged and marginalised species as much as connected scale forests, we need to know that but it doesn't mean we should not have Miyawaki forests.

TFA...?

The featured article. the fine article. the first argument. the final attempt.

As a rule of thumb if is associated to a fancy name, it has been invented before, and the plan will not fulfill its promises.

"Forests will reach a mature state in only a few years" is just other of this marketing statements that sound nice, but are wrong.

> Fuck minimum parking requirements, where are the minimum forest requirements?

I want a t-shirt with this phrase. Is simply brilliant

If your city cannot afford botanical gardens, then planting trees on sidewalks, more boulevards, and other places not only bestow ecological benefits but is also good for the human psyche and reduces crime.

https://www.fs.usda.gov/research/treesearch/40701

Does planting trees reduce crime?

Or are areas that have planted trees areas that also tend to have reduced crime?

The abstract of that paper indicates an inverse correlation between trees and crime, but stops well short of claiming or proving a causal relationship.

> Or are areas that have planted trees areas that also tend to have reduced crime?

Perhaps fake it till you make it?

Worth a try surely.

The correlation they saw was after controlling for potentially confounding variables, like income level, housing stock, density, and demographics, as explained in this article: https://caseytrees.org/2023/09/mythbusting-trees-and-crime/.

So of course it's not proof of causation, but reverse causation(nice neighborhoods lead to more trees planted) seems unlikely to explain the effect.

Indeed. Islington in London was famous for having few trees and lots of crime. Now it’s a nice fancy area that still doesn’t have a lot of trees.

There is about white collar crime lurking here somewhere.

The crime is understood to be street crime. The bankers and lawyers would have to decide to insider-trade on the pavement outside the pub, for this crime to become street crime. Or, kick people because street crime is often crime of violence.

So, get that suit on, start dealing ahead of the market, and kick a beggar. THEN you can contribute to the statistics.

I hope this isn’t a revelation to anyone at this point. Of course greenery reduces heat, but more than anything it means removing concrete, which mitigates the urban heat island effect. (Urban heat islands absorb heat energy during the day, amplifying extremes, and release heat at night, making it impossible for effective cooling.) And yet there is still so much resistance or otherwise apathy to the idea of planting more trees and removing space for vehicles — as if it’s merely some hippy-dippy shit only good for gentrification.

Planting more trees and removing space for vehicles are two different things; it is not necessary to make them dependent. Those who do, usually do it for their anti-vehicle agenda, and planting green is only an excuse / a tool, not the objective or intent to improve the environment.

If you want more space for parks and green, you can do it also other way. For example, like Hausmann did in Paris.

In a hierarchy of urban planning, I’d favor removing space for cars over demolishing precious space for affordable housing. To that effect, I wouldn’t point to Haussmann who bulldozed plenty of homes and neighborhoods for his unified vision of Paris connected by major thoroughfares. As a result, we have few parks and the city lacks any kind of real arboreal shelter except on some of the boulevards. He was a visionary, but he didn’t have scientific papers or the threat of climate change to contend with.

The idea I have in mind is that the control over cities has been wrested from its citizens. A special car commuting class has more comfort moving about a city like Paris than regular inhabitants — but at what cost and borne by whom? Removing space for cars means removing vehicles, which re-empowers city-dwellers, cleans the air, and cools the city.

In much of the US, the two are interdependent: to plant more trees on streets, for example, many US cities will need to trim the arterial roads that swallowed up neighborhood sidewalks half a century ago.

I wonder if they could cool down a desert; let's say, make nuclear reactors and plant them on the edge of Sahara, and do one thing with them: desalinate water from the sea; use the water to irrigate large portions of the desert, and plant them with bamboo; this will cool the desert, sequester CO2, and have global influence on the climate warming.

Back on the envelope calculations: 3.5 kWh/m^3 to desalinate water, 10 nuclear reactors, 1sq meter for a bamboo plant, you can water and grow 5.5 billion bamboo plant; let's say each plant fixes 10kg of CO2 per year, you reduce 10% of world's emissions in one clean sweep, for a total investment of maybe 100 billion USD

Desalination doesn't produce (freshwater + salt), it produces (freshwater + saltier water). Dealing with the waste brine is a challenge if you want to process that much in such a localized area.

The area is very clearly not "localized".

The real problem is that the cost would be outrageous.

If you go this route for greening the Sahara, you could allot 5% for the evaporation ponds to turn brine into dry salt.

There are other reasons it will never happen, but this one is solvable! :)

That’s a vast amount of salt. They can go from destabilising the world energy supply to messing with world salt supply.

you can't do mass change like that. This will change weather patterns could result in a lot of rain being sucked into the Sahara and make South America a desert. https://news.mongabay.com/2015/03/how-the-sahara-keeps-the-a...

Human activity has lead to the Sahara being much larger now than it was in the past. There are ongoing efforts (https://www.youtube.com/watch?v=WCli0gyNwL0) to try and keep the Sahara from growing any more.

well, anybody with a 100 billion can do that; we're in the age of such technology multipliers that private very rich men can undertake planet-scale geological projects without a sweat

There have been a couple attempts to do this previously. In India, there was one version used as a physical barrier on a customs line for 450 miles. Also happened to improve the area.

https://en.wikipedia.org/wiki/Inland_Customs_Line#Great_Hedg...

https://amocarroll.com/projects/tracing-the-great-salt-hedge

China has the China's Three-North Shelterbelt Program where they're trying to hold back the desert in North China and Inner Mongollia.

https://en.wikipedia.org/w/index.php?title=Three-North_Shelt...

Based on reports, it has issues with tree survival, yet seems to be making progress based on aerial surveys.

https://www.sciencedirect.com/science/article/pii/S259033221...

There's also an attempt in Africa in the Sahara that a bunch of countries signed on to. Unfortunately, their commitments have mostly amounted to talk without much funding or governmental support. Seen a few videos of locals who seems to believe in the idea, its just not getting much large scale help.

https://en.wikipedia.org/wiki/Great_Green_Wall_(Africa)

I also use Ecosia (https://www.ecosia.org/) as a web browser, and they supposedly plant trees based on number of searches and a percent diversion of search revenue. Seems to at least have some photographic evidence of money actually being spent somewhere.

Senegal's an example with desert work. Seems to have evidence that at least some amount of trees are being planted with videos (harder to falsify).

https://blog.ecosia.org/senegal/

https://blog.ecosia.org/tag/senegal/

Saudi Arabia is building a mega-project that's kinda like that:

https://www.youtube.com/watch?v=-13bKIS75Gk&ab_channel=TheIm...

Thanks for that. I wasn’t clear on how they power it. Solar? Oil?

You need a ton of water just to run the reactors and the droughts have already required ones that are in desert like the Palo Verde plant to reduce output.

I mean, you have the Mediterranean sea right there, build them 500m off shore, we have the technology

I have always been very curious as to why many cities do not push for more forests to cool down the place. I studied in a college with a lot of trees on campus and the temperature was at least 5 C cooler than just outside the college.

Because more housing is seen as a more immediate and higher need

Because parking spaces or other such things are more profitable for business owners and the city.

Nobody can monetarily profit from trees, unless you were to charge people money for time spent under their shade.

You act is if the people living there don't want parking spaces.

As city dweller, I really would like less parking in my city.

Turns out surface parking is a better $/sqft than garages once you count maintenance. This means that the core part of the city where density is greatest is ringed by a 2-5 block wide wasteland of surface lots. Its not great. Especially now that work from home is a thing and the divide between people who live here and people who drive here to work is obvious because the suburb people aren't here any more but their parking spaces still are

The parking spaces are still there because the city's 'density' or 'daytime population' was pumped by ecologically unsustainable commutes.

The US has never had a high level civic planning process or ability. Housing ends up built where-ever, and it's often cheapest to go built it in places with less regulation. Like wild frontiers in not even states. Or in areas outside of city limits as a tax dodge. There also aren't formal processes for renewing areas; instead informally they're allowed to decay and crime rise, and eventually reach a point where it becomes 'economically viable' for building something new.

Those lots exist because there's still enough whatever is desired in the city you live in, probably too much retail and office space. Probably not enough apartment / condo / housing space, but none of those investors want to admit their market was over-valued and de-value the present investments so they'll happily keep supply low and rents high.

Parking spaces by definition benefit people who drive, which usually means someone well out of walking distance. That leads to some interesting dynamics where people who are enough richer to have nice separated homes use their social status to demand parking everywhere even though the main thing people near those spaces get out of it is negative health impacts.

One interesting angle involves small businesses: you’ll often see owners interviewed complaining about losing parking spaces. This makes no sense for a local business, and there are decades of studies showing that pedestrian/transit/bike traffic generates more revenue for small businesses (if you’re already in the car, you’re probably continuing to a big store) but it makes total sense when you realize that the owners are far more likely to live out in the suburbs and are making the mistake of assuming this is also true of their customers. There’s a staple in some city planning debates of noting that the people complaining loudest about how their customers won’t stop if they can’t park right in front are often leaving their own cars in those spaces all day.

> pedestrian/transit/bike traffic generates more revenue for small businesses

Sure, if you have a walkable/transitable/bikeable city. If you don't, then losing parking spaces can be an issue.

I would have to walk for 24 Google Maps minutes to get to the nearest store of any kind. And I'm close; people farther down the main road that feeds my street could face almost an hour's walk each way (with no sidewalks or shoulders; you're walking in a ditch) to get to the same place. Several large hills along that route and a hot, muggy climate means that nobody is going to bike it.

My niece, from Colorado, came to visit her grandfather (my dad). She wanted to go for a hike in the South in July. I said sure, I'll take you. Five minutes into it, she said, "Now I know why everyone is fat here. This is miserable." And my reply was "Yes, and this isn't as hot or as humid as it gets. It's actually not that bad today."

We’re talking in the context of cities so I was only referring to more dense scenarios. I agree that rural or really low-density suburban communities are different.

The key point is really just the function of distance: people who live near a small shop will go there due to convenience. If it’s far enough to need a car, they’ll probably keep going to a bigger shop with lower prices because the cost of having and using the car is already incurred and the cost of doing anything else is greater.

> Sure, if you have a walkable/transitable/bikeable city. If you don't, then losing parking spaces can be an issue.

But a huge part of what makes cities terrible for walking/biking/transit is having too much parking.

Shop entrances being right next to the sidewalk is ENORMOUSLY more pleasant for pedestrians compared to needing to walk across a veritable sea of asphalt, as is the case in typical American strip malls and similar developments.

> I would have to walk for 24 Google Maps minutes to get to the nearest store of any kind.

Probably a zoning/density issue. We've intentionally designed our cities to be shit for walking and to our credit we've succeeded enormously.

> Five minutes into it, she said, "Now I know why everyone is fat here. This is miserable." And my reply was "Yes, and this isn't as hot or as humid as it gets. It's actually not that bad today."

Nope, that's not it at all. The American South has a somewhat similar climate to Japan, and even the warmer parts of Japan have way skinnier people.

I lived in Alabama for a couple years, and I'd say it's mostly just transportation design and culture around eating. I biked a bunch in Alabama and it was fucking terrible. That shit sucked. Granted, biking almost anywhere in the US is pretty bad, but Alabama was definitely worse than some of the other places I lived, and infrastructure was the biggest part of that.

I'd love to see fewer parking spaces if it meant better transit/walking/biking, and yeah trees are part of that (especially for walking).

Street parking in a lot of cities in america is notoriously "free". I think somebody wrote an article about how in SF, their car pays less rent per sqft than they do.

>their car pays less rent per sqft than they do

This shouldn't be surprising though. Cars don't need heating or cooling or sewage or a roof or ...

They often get most of that with a garage. No sewage is needed, though runoff from parking should really be treated before being dumped into waterways.

People who live there profit from the trees through quality of life benefits (such as being 5 degrees cooler). Maybe part of the problem is that a lot of landowners tend to not live in the land they own, so they can't see these profits.

I was talking about monetary profit not quality of life profit.

Money is just an abstraction for quality of life :)

In Britain I've seen trees planted in urban spaces. And then local residents come and pour rock-salt and weed-killer on the saplings there - because it stops them parking.

On the other hand in Sheffield there was a huge movement from residents to stop the cutting down of trees. Everyone I know there supported it.

> in Sheffield there was a huge movement from residents to stop the cutting down of trees

I cynically searched as I was sure the trees would all have been cut down.

They weren’t. There were wrongful arrest payouts, more trees planted and everyone started working together to plant more trees. Is this really correct?

https://en.m.wikipedia.org/wiki/Sheffield_tree_felling_prote...

I think about doing this. Just guerilla tree planting. Harvest saplings from where they're obviously not going to thrive, grab a foldable entrencher and just hit spots that need a bit of reforestation. However I suspect most of them wouldn't take and that there's a bit more to successful tree planting than I suppose.

I would have to ask my friends there to be sure, but AFAIK the campaign was successful, despite the plans being entrenched by long term contracts.

It is a pretty good example of why long term complex outsourcing is a bad idea.

Add a tax for those that don't have trees. There you have your incentive. It's so easy, unfortunately taxes aren't often used this way.

The whole point of a city is to concentrate human activity in a small area.

That doesn’t mean you can’t have trees: a high-rise building next to a park is quite dense, as are tree-lined streets.

The problem is those streets: the 20th century model focused on maximizing individual vehicle usage, which meant lots of open space for safe operation and subsidized storage. Cars can’t go around trees like pedestrians or bicyclists and owners don’t want branches falling on their parked cars, so anywhere there isn’t enough space for both it tended to result in more heat-amplifying asphalt.

Most land that isn’t already a park is privately owned. Most cities can’t afford to buy out a forests worth of real estate let alone clear it and replant it.

This feels misleading.

I totally believe that botanical gardens cool the air within them. That's what happens when you have an area full of trees and shade, with denser vegetation than a park.

But I have a hard time believing that they have any significant effect on the city air 5 or 10 blocks away, where the asphalt is baking in the sun.

So I'm not sure what the point of this article is, because it's not like we're going to replace half the blocks in a city with botanical gardens, as nice as that would be.

Meanwhile, the article claims claims planting trees on the street has less effect, but surely is far more important -- because it affects the whole city, rather than a small localized area in and around a botanic garden?

So there seems to be a major flaw in this article, in that it's comparing the cooling effects of various interventions (botanical gardens, street trees, etc.) but without ever specifying how the sizes or densities are being compared.

Honestly, I can't even imagine what a unit of comparison between botanical gardens and street trees would be, since botanical gardens replace streets and buildings, while street trees merely add to them. It's apples and oranges.

I don't see anywhere in TFA where it's implied that the temperature drops as an average, or that somehow it extends past the green area. I feel like you've been misled by a strawman that you created yourself.

Empirically, it extends a tiny bit past the green area.

When I go for walks in summer in my city, it's noticeable how the temperature drops while on the sidewalk when I walk past a green area as opposed to past a building.

Thermodynamically it must. High temperature will flow towards low temperature areas like a heat-sink, where it is cooled by the shade and vapour.

It’s actually the opposite. High temperature air rises (by expanding and becoming less dense), the void is filled with low temperature air. So a colder forest will start a wind outward of the forest towards the warmer areas, thereby distributing the colder air into the surrounding area.

Serves me right for thinking two-dimensionally!

> But I have a hard time believing that

Have you built your argument against the study on belief?

I think the article addresses this fairly well. In addition to shade, evaporation from open water and plant leaves contributes, as does the soil acting as a heat sink.

Botanical gardens are only slightly more effective than trees over roadways from their study, so shade is likely the strongest factor, but the others clearly play a part- from cooling down enough overnight compared to roadways and cement to the evaporation from the denser vegetation having a stronger effect.

The thing that I missed was how such a garden compared to an open, grass park. The difference in vegetation density would be clearer, I think, and might better explain the difference measured between trees over roads and gardens.

From an energy perspective it makes sense, since at least some of the solar energy hitting tree leaves is used for photosynthesis, and reducing Carbon out of its oxydized state. So it's not just accumulated/reflected like for pavement.

Effectively none of the incident energy is used for photosynthesis.

Much bigger effects are reflecting energy well above things that can store heat, and acting as evaporative coolers.

Interesting how easy it is to mitigate 5C - and yet we think the world is going to end if temps increase another 2C - when we are basically in an Ice Age and the Earth has only been cooler for brief periods of time in the last 500M years: https://www.climate.gov/news-features/climate-qa/whats-hotte...

Luckily, fossil fuels are going to get phazed out massively over the next 50 years strictly due to economics.

You are mistaking global for local, and 50 years is too late. I am positive I think some of us will survive.

Did you read the link you posted? Specifically the update at the top?

Easy to mitigate it in urban environments which are heat islands due to the low albedo of man-made surfaces. 99% of the earth, however, is not paved.

Reducing heat on a global scale is a wee bit more difficult.

The increase in temperature is just one of the issues. It has probably been mainly publicized as it's an easy "key performance indicator" to get the point across/that can be succinctly referred to. Sea level rise, ocean acidification, global weather pattern shifts, etc. are all also major problems.

They do have a significant effect. Trees scoop up rain from the soil, lift it through their trunks and up into the leaves where little mouths (stomata) in the leaves deposit that water back into the air in a process called transpiration.

It is actually in this way that places deep inland can still receive rainfall. Without this process clouds wouldn't be able to make it far inland.

Complete anecdote here, but I live on a park that is about two acres big. Its filled with large old (~100 years) trees and lawns, though it does also cram in a basketball court and two tennis courts. In the summer heat, when we walk around our area, the temperature astonishingly drops about 5 degrees once you get within 2-3 blocks of the park. Its striking in how noticeable it is. I have no idea why, but it seems even a bit of green space can have a big impact.

High temperature air rises (by expanding and becoming less dense), the void is filled with low temperature air. So a colder forest will start a wind outward of the forest towards the warmer areas, thereby distributing the colder air into the surrounding area.

You can see the same effect mostly in spring in coastal areas, when the land is heated faster than the sea. Hot air over land will rise, colder air from the sea will move in, causing thermal wind, making the coast a lot cooler. This can cause enough wind for kitesurfing or wingfoiling.

I think it's misleading for a worse reason: These trade temperature for humidity. They seem to work great as long as the temperatures don't go too high. They become hot ovens when they would be the most needed.

Its good to trade temperature for humidity

Reading past the headline, the effect is from trees providing shadow, and evaporating water cooling the air.

You don't need any actual botanical gardens.

But it’s probably the easiest and cheapest way. Another plus point would be creating habitat for smaller animals and morale boost for the city inhabitants

Well, both require making land available, and while amenity gardening is manageable, a botanical garden is often a research site that requires a lot of expertise to set up and maintain. Mind you, that's just fine, the county can and should hire people.

> botanical garden is often a research site that requires a lot of expertise to set up and maintain

But it doesn't have to be, right? It's just that we don't have very many, so the ones that do exist end up being research sites.

Looking out my window, I see trees planted on the sidewalk along a road.

It takes little space away from pedestrians, but provides a lot of shade. That seems both easier, cheaper and better that taking up whole city blocks.

We need more trees, i am shouting that for years.

Now, if only we can do something about the absolutely endemic heat desert effect we've created by caking our country in massive black asphalt parking lots and 6-lane freeways.

Nope, can't examine that. Parking lots are peak human design. The most logical design solution for our species.

Obligatory mention of Not Just Bikes:

https://www.youtube.com/@NotJustBikes/videos

"The road to hell is paved with asphalt" saw this here on HN not long ago - https://devonzuegel.com/the-road-to-hell-is-paved-with-aspha...

They mention less heat as one of the multiple benefits of pavers / bricks.

I used to dislike them by default - "They're bumpy". They're not bumpy. There's a shopping center in my town, and even a new Taco Bell, that use pavers for their parking lot, and I can't even notice.

We could probably do pavers for new parking lots and keep asphalt / concrete for heavy-duty stuff like interstates and roads over 30 MPH and not lose much except the up-front cost of pavers. (But hey if Taco Bell thinks they're worth it...)

"Bumpiness" could be climate related - I've spent a lot of time in the upper midwest US and Canada, the freeze/thaw cycles mean things move in the earth.

If you've got freeze/thaw cycles, then your asphalt roads will be bumpy as well. Trust me on that one.

Only if the foundations are bad and the road surface is not rated for the axle load of the vehicles that drive on it. I live in Norway where it is hovering around freezing just now. The only places where this affects the road is where water has penetrated the foundations in such a way as to wash away some support or where heavy vehicles have cracked the road surface allowing water in which subsequently freezes. If the road is properly constructed and maintained with sufficiently good drainage on both sides frost heave (telehiv in Norwegian) should not be a problem.

I grew up in Northern Norway, and pretty clearly there are a lot of roads with telehiv. ;-)

You're probably right about foundation quality. But there sure are a lot of roads that didn't get that right.

It might honestly be easier to fix freeze-thawed cracked pavers than having to rip up asphalt and lay it back down.

Every residential street should be paved with bricks or other paving stones, instead of asphalt. It's safer, because people drive more slowly. The maintenance costs are also lower.

Bricks and pavers are very difficult to plow safely. They are also more expensive than asphalt.

But for warm, affluent locations, they make sense.

But bumpy is good!!!! A bumpy street is one where you drive slowly and don't run over children riding bikes to school. A bumpy street is one where you pay attention. A bumpy street says "you may drive here but this is not a space _just_ for your car".

If only they were more common outside the Netherlands. I love my bumpy, brick, tree-lined, narrow, street.

TBF, my experience of america when I lived there, was that black asphalt was far less common than light grey (and thus higher albedo) concrete for both. Increasing albedo is considered to be one of the geo-engineering solutions to try.

I live in a place where we have a Tesco mall with a big parking lot nearby, but then I have to walk a path through a green area with mostly grass, but some trees and bushes as well.

The temperature difference is staggering. In hot summer, the parking lot is unbearable and the green area feels much better. In early spring/late autumn, the parking lot is uhm-okay (though still ugly), while walking through the green area gives you shivers: cool and wet wind.

Only in deep winter, during the freezing days, both areas feel the same.

I think this should be common knowledge that planting trees and having native green spaces in cities helps keep things cooler. In my neighborhood in Los Angeles, we have people who don't want trees in their yards and one who actually damaged a city planted tree in order to get rid of it. To a certain extent I get it, trees have to be maintained, which does cost money. We have a large and fast growing pepper tree in our yard, which is just over the line where the city would maintain it. We usually spend $700/year to have it trimmed back from hitting the house. I really appreciate how much shading it provides in the late afternoon in the summer.

Anecdotally, Spanish cities seem to have really beautiful and well-kept gardens.

Might have something to do with mitigating the hot climate. (Córdoba during the summer is a veritable oven.)

I wonder if the centers of cities are hotter now that they are all pavement and buildings than they were when they were grasslands or forests?

Could this contribute to warming?

Could warmer cities even cause us to overestimate the current temperature because the temperature 100 years ago on a prairie was less than the temperature today in a parking lot?

Do you want to account for the people living denser in those cities and thus freeing up room in more rural areas?

I didn’t notice it until I got a motorcycle and started riding, because there’s very little between you and the environment and you’re moving so fast you can definitely feel the cooler and hotter parts of a city.

Areas with trees, not necessarily sharing the road definitely feel a few degrees cooler

Hmm, what is the general availability of water resources these would need in areas that would benefit most of them? If there is already droughts I don't think too much water usage could be afforded adding more vegetation.

If you are planting native trees there should be no problem - there have been droughts before and so the trees can handle them. You might need to water them for the first 5 years, but after that they should be okay.

Select trees that are not native (or native species but from a very different location) and you can run into problems.

Native trees aren't always the 'best' option in modified urban environments. Just becuase they grew on what used to be there doesn't mean they will like what is there now

Another reason to do guerrilla gardening, or seed bombs:

https://en.m.wikipedia.org/wiki/Seed_ball#Seed_bombing

> seed bombing

Please don't encourage anybody to do this. Let it to people that knows what they are doing. Invasive species burn millions and aren't a joke

I'm not sure. I live in London, 51 degrees north. We have a lot of parks in London, but the bus stops near them still have deep grooves of melted asphalt from recent heatwaves.

Perhaps it would be even worse without the parks? This article suggests that variation in temperature across the city does correlate with vegetation cover:

> the Kilburn and South Hampstead area, with 38% vegetation cover, experienced heat over 7°C hotter than Regent’s Park, with 89% vegetation cover, a short distance away.

https://www.pbctoday.co.uk/news/digital-construction-news/bi...

> This article suggests

Is more like a proven fact. Temperatures measured on hard landscape of modern parks based on stone is consistently higher than on old fashioned parks with big trees and fallen leaves.

Sadly, cities still love this sun scorched inhospitable parks with passion because:

1) civil responsibility. A branch can kill a person and politicians hate this possibility

2) they are much easier to tidy up and much cheaper to maintain. Cheaper in the sense of "people will pay for their air conditioner, not us".

3) Vehicles can pass easily over stone surfaces (Also cleaning vehicles). Is not so easy to clean and drive over gravel

I used to live in Chicago, and they managed this by putting a concrete pad at the bus stops that were high-frequency enough to get the grooves. The concrete pads are not bus-sized! They are only placed where the bus wheels are when the bus comes to a stop, with a little bit of a buffer since the bus doesn't stop in exactly the same place every time.

> but the bus stops near them still have deep grooves of melted asphalt from recent heatwaves.

Are you sure it isn’t from massively heavy busses repeatedly taking the same route across ‘not-that-hard’ tarmac?

Any grass can cool the city 5°C but city need to maintain it and first of all, need to sacrifice the money the city would make off of building another four flats on it

Any grass can not cool the city by 5c

I hope that the renewed interest in urban gardens and the appreciation for plant life in urban landscapes persists. The benefits can be wild in terms of improved quality of life for those living in the city.

I live very near an urban core that is undergoing rapid development and densification. That core is part of a larger planned area that includes apartments, condos, town houses, and suburban style homes going back more than 50 years. The nearby suburban areas are walkable, and almost entirely embedded in so much greenery it's virtually a wildlife preserve. A local association owns some significant percentage of the land and has strict rules about development on their property which keeps it out of the hands of developers and well forested.

My understanding was that all of these thousands of acres were virtually tree free farmland when it was selected for development. Now the entire area is absolutely filled with 30-70 foot (10-20 meter or so) trees planted when development started, dense undergrowth, and absolutely chock full of various kinds of wildlife like deer, foxes, raptors, and so on. Yards are allowed, but not really required, so many people have just let them go fallow and return to nature, or keep minimal outdoor areas for lawn furniture or play areas for their kids.

The urban area needs a place for rainwater runoff to go, so the runoff areas dump into artificial streams which have been designated as parks, and provided with paved trails, and bridges and so on. They too have become heavily forested, the only sign that they're part of the local urban infrastructure is the occasional manhole cover. The runoff condenses into a selection of local artificial lakes that open up opportunities for waterfront property and parks, and personal watercraft and recreation areas.

I live in a suburban home, 3 miles from the middle of the urban core which features an Apple store and other big named retailers, as well as offices, restaurants, recreation etc. It's a nice walk on weekends or evenings. The core is connected into the nearby major city and other nearby urban areas and the local airport via light rail.

In the summer, we're about 5-10 deg F cooler than all of the surrounding areas, and much more humid in general. Because of the trees, we get very little wind. It can sometimes be difficult to predict how to dress when going out as our house sits even cooler than that, and stepping outside is still not representative of the way it feels in other nearby areas. It can be cold in our home in the early fall and late spring when the outside sits at around 20 deg C or 70 deg F.

In some parts of the world this may sound absolutely normal, but here in the U.S. it's absolutely bonkers that it exists. My understanding was that it was explicitly patterned on a "more European" style of land development.

shame they used an image of a table, instead of a html table. [accessibility fail]

Except plants increase the humidity, exasperating conditions.

But they make it cooler more than they make it more humid

The chart and table in that article are confusing. They seem to indicate that if a city has botanical gardens, wetlands, green walls, street trees, balconies, permeable paving, woodlands, playgrounds, adopted public spaces, and mixed biomes, the air temperature would be reduced by 35°C. If so, I'm prepared to ban all these things to prevent our cities from becoming frozen hellscapes.

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