Can we please stop drawing trees on top of skyscrapers?

March 26, 2013 5:35 AM

Want to make a skyscraper look trendy and sustainable? Put a tree on it. Or better yet, dozens. However, "There are plenty of scientific reasons why skyscrapers don’t—and probably won’t—have trees, at least not to the heights which many architects propose. Life sucks up there. For you, for me, for trees, and just about everything else except peregrine falcons."

Mentioned in the link as an exception to this rule is Bosco Verticale in Milan, due to be finished some time this year.

posted by daisyk (65 comments total)

What I took away from that is that our skyscrapers need more raptors.
posted by atrazine at 5:39 AM on March 26, 2013 [13 favorites]

I don't buy his comparison of skyscrapers to mountains. Skyscrapers are 500-1000 feet above ground level. That hardly qualifies them for hill status let alone mountains. Even then, drive through central Pennsylvania and see all of the trees on top of the Appalachian Mountains.
posted by nolnacs at 5:41 AM on March 26, 2013 [5 favorites]

Trees on skyscrapers are like promises of "helping 3rd world villages" from new technology or "think of the children" cries for new legislation.
posted by DU at 5:41 AM on March 26, 2013 [4 favorites]

Whenever I see images like the ones in the article, I always wonder if they have to dedicate the entire floor below the trees to the root systems?
posted by Thorzdad at 5:42 AM on March 26, 2013 [8 favorites]

If a tree falls off of a 50 story skyscraper and no one's on the 25th floor to hear it, does it make a sound when it hits ground level?
posted by samsara at 5:43 AM on March 26, 2013 [12 favorites]

Vertical gardens have been a dream of architects for quite a while. In the last several decades the idea keeps popping up, but they are all just fantasies. Your second link is the first time I have seen a photo of a tree being lifted on a crane, which has a distinct veneer of reality to it. So maybe someone is being foolish enough to go through with it. The problem is just the economics make no sense. You can plant a garden a few miles away for a tiny fraction of the price. Of course these days the rich are so rich they can waste as much money as they want.
posted by bitslayer at 5:45 AM on March 26, 2013 [1 favorite]

What I took away from that is that our skyscrapers need more raptors.

My takeaway too! We're just recreating the wrong kind of environment.
posted by Miko at 5:47 AM on March 26, 2013 [1 favorite]

There actually was a tree growing on the roof of this building but that's only because it was abandoned for two decades. They've been renovating it now and have cut the tree down.
posted by octothorpe at 5:47 AM on March 26, 2013

It’s hot, cold, windy, the rain lashes at you, and the snow and sleet pelt you at high velocity. Life for city trees is hard enough on the ground. I can’t imagine what it’s like at 500 feet, where nearly every climate variable is more extreme than at street level.

I was on a hill that was 500 feet above sea level yesterday. There were many, many trees on it. Different trees than at sea level, but trees.

So, yeah, I'm with nolnacs.
posted by His thoughts were red thoughts at 5:49 AM on March 26, 2013 [2 favorites]

I'm for Hundertwasser's tree tenants, myself.
posted by sonascope at 5:49 AM on March 26, 2013 [4 favorites]

Keep in mind your hilltop and mountain trees have metres and metres of dirt and rock to hang onto. Like, an extra floor or two. Deep roots. Other trees to cover them. Ecosystems to support them - insects and animals that fertilize them and help them retain water. Huge networks of fungi intertwined with their roots providing them with nutrients. You can't just cram a massive tree into a foot of dirt on top of your highrise and expect it to behave like a forest. The forest is deeper than the eye.
posted by Jilder at 5:53 AM on March 26, 2013 [19 favorites]

Vertical gardens have been a dream of architects for quite a while

You mean like a green wall? Not a fantasy.
posted by the man of twists and turns at 5:54 AM on March 26, 2013 [3 favorites]

I found this article pretty disappointing, since I love the look of trees atop buildings—whether the skyscraper forests in these pictures or just shrubs that have forced their own roots into cracks in the facades of regular buildings. I do agree that regardless of what the architects draw, these trees are unlikely to ever really be planted once the designs get built.

I think it will be really interesting to see how the Bosco Verticale pans out. How will the concrete stand up to the root systems of all those trees?

The world's first vertical farm was opened last year in Singapore. So far its vegetables are more expensive than the conventionally-grown kind but they're hoping to decrease the price with increased production. It seems to me that Singapore is an obvious place to try this out (okay economy, limited land).
posted by daisyk at 5:55 AM on March 26, 2013 [5 favorites]

>What I took away from that is that our skyscrapers need more raptors.

My takeaway too! We're just recreating the wrong kind of environment.

We could stock the trees with squirrels. This would annoy the tenants but please the raptors.
posted by GenjiandProust at 5:56 AM on March 26, 2013 [3 favorites]

...or, you know, hang underperforming VPs in cages to be devoured slowly by vultures. Whichever.
posted by GenjiandProust at 5:56 AM on March 26, 2013 [7 favorites]

I don't buy his comparison of skyscrapers to mountains. Skyscrapers are 500-1000 feet above ground level. That hardly qualifies them for hill status let alone mountains.

A thousand feet above ground level on top of a skyscraper is probably not the same thing as on the ground on top of a thousand feet hill in terms of weather. Wind speed and patterns are definitely going to be different for one thing. Futhremore, atmospheric air is mostly warmed from the bottom up, from solar heat absorbed by the ground so I'm guessing the top of an isolated skyscraper will be significantly colder than the equivalent altitude on a hill or mountainside.
posted by Dr Dracator at 5:58 AM on March 26, 2013 [7 favorites]

Keep in mind your hilltop and mountain trees have metres and metres of dirt and rock to hang onto. Like, an extra floor or two...

Yes, it is an engineering challenge. But the article appears to contend that trees couldn't survive at skyscraper height, which is just silly.
posted by His thoughts were red thoughts at 5:59 AM on March 26, 2013 [3 favorites]

I am going to be in Milan next month - I will have to see if I can check on the progress of Bosco Verticale, that looks interesting!

I'm all for attempts to integrate more of the natural world in urban areas and I guess you have to kiss a lot of frogs before you get to the feasible projects so thumbs up for attempts in that direction. I like a lot of the projects in this prior post: Sky-high gardens and rooftop oases - a little less ambitious than forests and full size trees, but more than I'd have though was possible.
posted by madamjujujive at 6:04 AM on March 26, 2013 [1 favorite]

I live on a hill 600 ft above sea (well, lake) level with very little windbreak (ie we get a lot of weather, most of it horizontal) and we have lots of trees of different kinds, many of which I planted myself. Trees are extraordinarily resilient things. Many will happily grow in a bucket, as you will see if you visit your local nursery. Cedars can grow on bare rock, and survive for hundreds or even thousands of years (there are some of these ten miles away from me). Moreover, most trees don't have deep root systems. They have broad root systems. The mineral soil generally begins 12-24" below the organic soil layer, so there's nothing much down there for them.

The idea that they need some kind of perfect, complex ecosystem to survive is just wrong. Go to London and look at the plane trees growing out of the cracked sidewalk, surrounded by diesel fumes and drunks pissing on them.
posted by unSane at 6:05 AM on March 26, 2013 [10 favorites]

But the article appears to contend that trees couldn't survive at skyscraper height, which is just silly.

Forests can. Individual trees will have a hard time, especially without, as others are mentioning upthread, the rich ecosystem in a forest floor.

On a real hilltop, the trees can share the load of being a windbreak and absorbing/coping with temperature spikes. But stuck up there in ones and twos, alone, exposed directly to the elements... well, let's just say that's Not Their Happy Place. They might be able to survive, but are unlikely to thrive the same way they would at street level, where the buildings serve as shade and windbreak.
posted by Malor at 6:07 AM on March 26, 2013 [3 favorites]

As someone recently adapted to urban planning, the ghost people should go too. New design schemes always show people at scale pantomimed into the setting for new developments.

(like this, also linked from PSM:
http://io9.com/what-will-human-cultures-be-like-in-100-years-453934475)

Anyone who's been to community meetings before has seen them, they don't make the project any more attractive and they're starting to freak people out.
posted by Reasonably Everything Happens at 6:07 AM on March 26, 2013

Huh.

Theoretically,

Let's say someone wanted to reforest a large amount of land, where would be most effective and how would you even begin?
posted by The Whelk at 6:11 AM on March 26, 2013

Let's say someone wanted to reforest a large amount of land, where would be most effective and how would you even begin?

Detroit, I think.
posted by sonascope at 6:16 AM on March 26, 2013 [3 favorites]

I like a lot of the projects in this prior post: Sky-high gardens and rooftop oases - a little less ambitious than forests and full size trees, but more than I'd have though was possible.

I think this is where the article fails; big trees may not be practicable, but roof gardens are totally doable and can really help reduce ecological impacts. They should be encouraged.
posted by His thoughts were red thoughts at 6:17 AM on March 26, 2013 [6 favorites]

On tree tenants, I couldn't find a better link because I was on a train fussing with a little telephone, but here's a better bit.
posted by sonascope at 6:18 AM on March 26, 2013 [3 favorites]

Yes, it is an engineering challenge. But the article appears to contend that trees couldn't survive at skyscraper height, which is just silly.

The author contends that there are many challenges to a tree's survival and that putting them on top of buildings is a bad idea, trendy for renderings but alltogether impractical. The author doesn't say that they out-and-out couldn't survive.
posted by entropone at 6:26 AM on March 26, 2013 [1 favorite]

DU: "Trees on skyscrapers are like promises of "helping 3rd world villages" from new technology or "think of the children" cries for new legislation."

No, but green roofs and water recycling systems are becoming increasingly popular on new buildings, and are actually quite a good thing for densely-populated urban environments -- it reduces the urban heat island effect, reduces water usage, relieves burdens on stormwater systems, and decreases the overall amount of runoff (water in rivers is a good thing, but not when that water has been "filtered" through a Manhattan street).

Trees on tops of skyscrapers might be a bad idea (especially since trees fall), but putting other foliage up there definitely isn't.
posted by schmod at 6:31 AM on March 26, 2013 [2 favorites]

I think the author's issue is with the drawings architects make, like this one. This type of greenery is not suitable for tall buildings, for a number of reasons. Lots of other types of green are great. Look at the work of Patrick Leblanc - a vertical garden genius
posted by mumimor at 6:36 AM on March 26, 2013

My take-away is that skyscrapers are savage, inhospitable chunks of architecture, architects know it, and they keep trying to put "Nature Band-Aids" on it to soften the emotional toll it takes on people who have to inhabit such inhumane circumstances.

And the author knows it's impractical and not working.
posted by Pirate-Bartender-Zombie-Monkey at 6:37 AM on March 26, 2013 [8 favorites]

I was on a hill that was 500 feet above sea level yesterday. There were many, many trees on it. Different trees than at sea level, but trees.

There is a huge difference between being on the slope of a hill at 500 feet above ground and being at the top of a tower 500 feet above ground. The tree on the hill has ground friction slowing the wind, and usually has a bunch of other trees around it doing so as well.

Here's a wind profile calculator. Make sure, since we're talking about skyscrapers, to set the roughness level to 4 (as per the table below.) You'll find a 5m/s wind (about 11mph) at the surface means you'll have nearly a 20 m/s (44mph) wind at 150m, which is very close to 500' (492.6', to be more precise.)

That's what a tree on a 500' tower is living through -- or, possibly, failing to live through.
posted by eriko at 6:43 AM on March 26, 2013 [5 favorites]

They put trees on towers in 14 century Lucca.
posted by Segundus at 6:45 AM on March 26, 2013 [5 favorites]

What I took away from that is that our skyscrapers need more raptors.

For reasons I can't adequately explain, my non-urban graduate school department was in, roughly, a sky-scraper. For reasons I also can't explain, there were windows (not in the graduate student offices mind you), user openable windows, all the way up. Peregrine falcons live and make babies on the roof. Peregrine falcons are surprising large birds flying death machines. From the remains you would find on the sidewalk, pigeon vs. falcon is roughly like pigeon vs. rail-gun. So, after spending X hours in my windowless office I would go out into the hallway and, in the openable window, would be a large flying predator, imperturbed, clearly a manifestation of my own inner trauma, tracking me as a went down the hall.

As far as I know, there weren't any suicides *in* that building.
posted by ennui.bz at 6:47 AM on March 26, 2013 [5 favorites]

Thank you for posting that, sonascope! I hadn't heard of the 'tree tenants' idea before and it's beautiful.
posted by daisyk at 6:53 AM on March 26, 2013 [1 favorite]

Ecology does matter, they have been seriously planting trees in Israel for many decades, to great benefit, but still no one would mistake it for the north woods. There are many small trees on balcony's, few significant apple harvests.
posted by sammyo at 6:58 AM on March 26, 2013

Let's say someone wanted to reforest a large amount of land, where would be most effective and how would you even begin?


Wait.
posted by unSane at 7:00 AM on March 26, 2013 [4 favorites]

(I'm not really kidding about that. Where we live there is a lot of reforestation going on as agricultural land is going back to wilderness. I have about 20 acres which was farmed until about 7 years ago. I've planted a couple of thousand trees but it doesn't really make a dent in 20 acres. There's a natural progression to reforestation... round here you get the early adopters like ash and poplar, and then some tougher stuff like maple and beech and finally some of it will go to white pine if you wait long enough. If you try to short-cut it you make a lot of work and the results are often sub-ideal, or monocultures. If your aim is forestry then of course that's what you want and you're talking about a plantation, but if it's a gosh darn forest you want, then, wait.

There are a few things you can do to improve matters in terms of soil preparation and so on, like making mounds and pits. But the trees that self-seed tend to do MUCH better than ones you plant, and usually in a few years will have outpaced them, even if the plantings started out much bigger)
posted by unSane at 7:06 AM on March 26, 2013 [1 favorite]

Forget the trees, every skyscraper should have a wind generator on it.
posted by freakazoid at 7:16 AM on March 26, 2013 [2 favorites]

Cedars can grow on bare rock, and survive for hundreds or even thousands of years...

I don't have any problems with trees on buildings but I think there's a difference in that those cedars are sustained by the watershed of the hill or cliff top.
posted by bonobothegreat at 7:29 AM on March 26, 2013

This article is way too pessimistic. You can avoid most of those problems by balancing a cruise ship on top of your skyscraper for the trees to live in.
posted by jhc at 7:29 AM on March 26, 2013 [3 favorites]

What I took away from that is that our skyscrapers need more raptors.

Q
posted by kirkaracha at 7:33 AM on March 26, 2013 [1 favorite]

I think there's a difference in that those cedars are sustained by the watershed of the hill or cliff top.

Have you seen those cedars? I have. They are literally growing out of tiny crevices. They're tiny, even though they're hundreds of years old, because they survive on almost nothing.

This one is huge. For years climbers used to ignore them because they thought they were saplings.
posted by unSane at 7:37 AM on March 26, 2013

You can avoid most of those problems by balancing a cruise ship on top of your skyscraper for the trees to live in.

Holy Crap! I feel I am pretty immune to resort architectural shenanigans but nevertheless: Holy Crap!
posted by shothotbot at 7:53 AM on March 26, 2013

unSane, we're in the same situation. I am planning to sow my forest, which is good for ecology, but means I'll never really see it. So I've instructed my daughters they have to care for it. I imagine my grandchildren climbing in the oaks I sow.
My grandfather planted a small wood when I was a child, which has never grown above 10 feet and is full of crooked trees. It's very dense and rich in wild-life, though. Experts tell me the problem was the use of imported saplings, unable to thrive in the local climate.
posted by mumimor at 8:14 AM on March 26, 2013

Have you seen those cedars?

I'm just saying that the trees on buildings are in a more precarious position, having to rely on people (to make sure they get enough water) for their entire lifespan.

That cliff face is cracked and eroded, so the sponginess of the material above and in the fissures of the rock keep moist what little soil exists around and in the cracks behind those trees. I don't think they'd survive very long in a clay pot on a balcony without proper care.
posted by bonobothegreat at 8:22 AM on March 26, 2013

The problem with trees and high rises is not that the trees won't grow. Sure they will. The problem is that trees are heavy, trees get old and sick, and what goes up must come down.

Trees put roots everywhere, and one of the ways hillsides get eroded is that those roots get into the cracks, swell up, and expand the cracks, eventually fracturing the rock. This is not a dynamic you want to encourage on a building, which unlike the hillside isn't fairly solid all the way to ground level. The trees can survive the skyscraper environment I'm sure, but it's the skyscraper I would worry about if you get a bunch of trees on the roof.
posted by localroger at 8:25 AM on March 26, 2013 [4 favorites]

I don't imagine they're just spreading a foot of soil on the roof and abandoning them to nature.
posted by unSane at 8:33 AM on March 26, 2013 [1 favorite]

Don't stop drawing trees on buildings. Start genetically engineering tougher trees.
posted by jeffamaphone at 9:22 AM on March 26, 2013 [1 favorite]

In an interesting, and totally unexpected development, the worlds tallest western Hemlock (a type of evergreen tree) is only about 18' tall from root to crown. Somehow its seeds (pinecone) found its way into a bole near the top of a coastal redwood in Humboldt county. Boles (a big flat spot in the trunk where it branches out usually caused by the crown of the tree being hit by lightning or wind and dying/falling off) collect a lot of debris like falling needles and bird poop (and seemingly seeds) and support a very diverse ecosystem. Noone thought that the tree canopy in these forests would be exciting, interesting places until they looked.
posted by bartonlong at 9:26 AM on March 26, 2013 [1 favorite]

I see the rendering in the article and all I can think is Bioshock: Vertical Forest.
posted by jscott at 9:50 AM on March 26, 2013

A rooftop forest might contribute to the health of the building's inhabitants when people start getting tick bites on their smoking breaks.
posted by RobotVoodooPower at 11:14 AM on March 26, 2013

Work begins on 'double helix' skyscraper in Taipei
posted by homunculus at 11:16 AM on March 26, 2013

Trees certainly can grow on top of skyscrapers; they grow on much harsher sites on the tops of cliffs, or on the sides of mountains. The issue is engineering in order to manage a volume of soil adequate to support a tree, and engineering in order to make that soil able to drain efficiently from the top of a building. They would only need irrigation depending on the amount and type of soil. What is commonly used in the built environment now is something called Cornell structural soil, which can be used in areas of high traffic without compacting the soil.
But certainly the exposure the trees with experience might cause them to grow in a contorted manner, and the actuality of managing trees on a site like that could make it not worth doing. It's much easier to grow mosses and smaller plants and manage those than trees. But I think it could be worth the effort.
posted by Red Loop at 11:34 AM on March 26, 2013

Is this a foolish trend? Or was the foolish trend the one of not drawing trees on skyscrapers before now?
posted by PJMcPrettypants at 1:42 PM on March 26, 2013

His thoughts were red thoughts: It’s hot, cold, windy, the rain lashes at you, and the snow and sleet pelt you at high velocity. Life for city trees is hard enough on the ground. I can’t imagine what it’s like at 500 feet, where nearly every climate variable is more extreme than at street level.

I was on a hill that was 500 feet above sea level yesterday. There were many, many trees on it. Different trees than at sea level, but trees.

So, yeah, I'm with nolnacs.

My house is at 200' above city level. It's a bit windy, and sometimes the 40+' high trees drop limbs in storms... just like on the plains. 500' is just a slightly different landscaping order to Mother Nature. Slightly.

That being said, the reason we don't put trees on top of buildings probably has more to do with the liability of those broken limbs than anything else. Any decent-sized limb would become a high-velocity spear at street level.
posted by IAmBroom at 2:30 PM on March 26, 2013

localroger: Trees put roots everywhere, and one of the ways hillsides get eroded is that those roots get into the cracks, swell up, and expand the cracks, eventually fracturing the rock.

That's not true for all trees. Plant ornamental plums, for instance, and you can damn near keep the roots in place with a sharp glance every Spring.
posted by IAmBroom at 2:33 PM on March 26, 2013

They put trees on towers in 14 century Lucca.

They also turned one of the city walls into a promenade with trees and lawns and footpaths. Putting trees on stuff is an old ambition and is not likely to go away.
posted by NoraReed at 3:02 PM on March 26, 2013

Why spoil the beauty of Man's achievements by adding the ever-decaying products of Nature?
posted by Charlemagne In Sweatpants at 3:04 PM on March 26, 2013 [2 favorites]

Have you seen those cedars?

Cedars on rocky mountainside = marvel of centuries of adaptation and evolution
Trees on top of skyscrapers = not so much
posted by Thorzdad at 3:29 PM on March 26, 2013

Clearly, what's needed is a hybrid falcon-tree.
posted by XMLicious at 4:50 PM on March 26, 2013 [2 favorites]

Instead of putting trees on skyscrapers, why don't we make skyscrapers out of trees?

Rather than building with two-by-fours, modern-day wood construction would be accomplished using state-of-the-art methods based on super-compressed mass timber panels – essentially giant, sturdy Lego-like assembly. The compression also contributes to protecting against fire, which Green concedes is the first question he gets when he talks about building with wood. These denser wood building blocks are actually difficult to burn – like a big fat tree stump in a fireplace – and would of course exist within the context of 21st-century fire suppression systems, including sprinklers.

The Case For Tall Wood Buildings (PDF), from The Wood Enterprise Coalition
posted by the man of twists and turns at 7:08 PM on March 26, 2013

It better be rot-proof too, especially after the sprinklers go off.

Also, if I was a bazillionaire I would build a wooden skyscraper in the waterfront district that could be laid down to double as a yacht. Or perhaps as a pirate ship.
posted by XMLicious at 7:21 PM on March 26, 2013

Am I the only one who always assumed those sorts of trees would be fake and plastic?
posted by jenfullmoon at 7:33 PM on March 26, 2013 [1 favorite]

Let's say someone wanted to reforest a large amount of land, where would be most effective and how would you even begin?

Reforestation has actually been happening since the beginning of the colonial period, although the most significant impact on forests was agricultural clearing of the late 19th and early 20th centuries. This inspired the conservation movement and beginning in the 1920s policy changes (and vastly increased per-acre productivity) have meant net increases in forestation, especially in the northeast and south of the US. The housing boom of the 2000s seems to have increased clear-cutting for development, though.

Anyway, there's more consciousness of biodiversity these days -- habitat restoration isn't just about trees, it's about watersheds, wetlands, prairies, and many other types of biome. Wetlands in particular are still disappearing at an alarming rate. The public is less likely to see "nature" in something that doesn't look like a traditional park. My city has a greenbelt system that channels stormwater runoff, and was allowed to grow as junk-tree forests including many invasive species such as garlic mustard. Currently they are cutting many trees and restoring prairie grasses, which actually accomplishes the runoff retention and filtering much better, and this is upsetting homeowners who thought they had a nice stand of trees out back.
posted by dhartung at 11:05 PM on March 26, 2013 [3 favorites]

Charlemagne In Sweatpants: Why spoil the beauty of Man's achievements by adding the ever-decaying products of Nature?

That's sarcasm, right?
posted by IAmBroom at 10:56 AM on March 28, 2013

Or let's put the trees at street level! Does vegetation encourage or suppress urban crime? Evidence from Philadelphia, PA (Via)

The present research analyzes the association of vegetation with crime in a case study of Philadelphia, Pennsylvania. We examine rates of assaults, robberies, burglaries, and thefts in relation to remotely sensed vegetation abundance at the Census tract level. We employ choropleth mapping, correlation, ordinary least squares regression, and spatial econometric modeling to examine the influence of vegetation on various crime types while controlling for tract-level socioeconomic indicators. Results indicate that vegetation abundance is significantly associated with lower rates of assault, robbery, and burglary, but not theft.

posted by the man of twists and turns at 5:57 PM on April 2, 2013