If I were a tree I’d be starting to get very worried. There was no need to worry back when roof “gardens” were first proposed as they didn’t seem concerned about plants. Besides, there was still significant garden at ground level. However, the idea that Nature was something to be looked at rather than experienced was planted. Also, having anything called a “garden” on the roof suggested the ground plane could now be used for other things.
In the eighties Ken Yeang produced some wonderful drawings of towers covered in plants and with spaces for trees to grow as part of an integrated building services system. The first built one was his 1992 Menara Meshinaga building.
Integrating rainwater collection, plants and biological waste recycling into a building system remains an excellent idea but the problem is that expensive structure is used to enclose large volumes of space to create “sky courts” for plants that don’t pay the rent. It’s a question of building economics and the multiple benefits of vegetation resist quantification. (This doesn’t mean people haven’t tried, or aren’t trying now.) It makes little sense to use significant structure to define large voids unless there’s going to be significant payback. There were big holes in these proposals. They were visually arresting because we‘d not seen anything like it before, but they were also unfeasible and never became mainstream.
Around the same time, people began to realise the benefits that growing plants on rooftops might have for stormwater runoff, heat-island effect, insulation and biodiversity and, not to mention, make us feel good about ourselves, and all for little extra cost! Green roofs returned some of the benefits that building on a piece of land had taken away. Ultimately however, representing these benefits – especially the one about us feeling good about ourselves –became more important than actually providing them. [c.f. The Demise of the Green Roof] In any case, it was all possible with only a small degree of construction complication as long as the greening bits were limited to grass or meadow plants.
For all the good they might do or might have done, the main problem with green roofs as far as representing green-ness was concerned, was that they were up on the roof where nobody could see them. One solution was to tilt the roof and, accordingly, we went through a stage of variously inclined and bulbous green roofs.
This must have resulted in too much unusable building volume because resolutely vertical “living walls” came next. Most people’s first architectural encounter was probably Jean Nouvel’s 2006 Musée de Quai Branly (with green wall by Patrick Blanc) and the second was probably Herzog de Meuron’s 2007 CaixaForum Madrid building.
We’d never seen buildings do this before. These two bookend and largely constitute The Golden Age of Living Walls. Brave attempts to prettify car parks and municipal buildings often underestimated the amount of maintenance required and ended up giving green walls a bad name. They simply required too much maintenance to ever be viable on public buildings.
Europeans have always liked to grow things on the upper floor balconies and terraces of apartment buildings, particularly so in Milan. Look at this next photograph. Apartments line a street with more than the usual amount of trees but people on upper floors want to grow their own where they can see them. 
The deal with apartment buildings such as this next one in Paris by Edouard Francois is that, in return for maintaining the plants, residents get to have plants outside their window as if it were a garden on land they could see through their window.
This is a photo from 2017 of M6B2 Tower of Biodiversity in Paris, again by Edouard Francois, and when the plants hadn’t yet been added. The entire building is wrapped in a plant-friendly trellis. No doubt Inhabitat has some more recent images.
This brings us to Stefano Boeri’s 2014 Bosco Verticale (“Vertical Forest”). Let’s be clear on this: Vertical Forest is about horticulture, not forestry. After five years, the trees and plants all seem to have reached their optimum sizes, and there are no dead patches, or noticeable differences due to aspect.
On the south side of Vertical Forest is a large park having sixteen “circular forests” of single species. It’s pleasant, but it’s landscaping not forestry. 
Apartments aren’t cheap – a low-floor 80 sq.m apartment will set you back €512,000 (US$570,000) while a 200 sq.m penthouse costs around €1.6 mil. (US$1.75 mil.) This is about 20-40% more than comparably-sized apartments nearby. Nevertheless, making something like this work is a huge achievement, integrating horticultural expertise with pedestrian safety and structural concerns. Accordingly, Boeri’s office has been asked to produce vertical forests for Paris (2017), China “Vertical Forest City” (2017), Antwerp (2018), Eindhoven (2018), Cairo (2019), Utrech (2019), Tirana (2030) … 
Clearly, vertical forests are a product and part of the appeal is that people can have bigger and better plants outside their windows. This is not only more convincing as garden, but also watered, tended and maintained as a building service charge – and that’s fine. My concern here is not whether vertical forests are a new type of cosmetic facade or an integrated part of some building or urban ecosystem. Some will be and some won’t. Plants being plants, there’s always going to be some organism that will appreciate them. Moreover, benefits such as photosynthesis, of plants not retaining heat, and the moisture retention properties of the soil they grow in are going to be present no matter how marginal or at what cost of getting the plants up there and keeping them alive. Vertical forests don’t require expensive structure, they are highly visible and attractive from all sides. A balance between living wall and the proposals of Ken Yeang seems to have been found. What’s not to like?
I’m suspicious of any kind of any building or part of a building that is claimed to replicate some function of Nature, specifically those traditionally performed by trees.
Remember what happened when artificial lighting and artificial ventilation began to supplement natural lighting and ventilation? They quickly became substitutes for it and various efficiencies of planning and construction meant bathrooms and kitchens were no longer designed to have those things called windows. This all happened quite a while ago and today we don’t think twice about windowless bathrooms and kitchens in tower apartments (or even detached houses). We never looked back. Hong Kong remains the last pocket of resistance. [c.f. Plan B]
The Objectification of Trees
Consider this next project by arch tree-objectifier, Thomas Heatherwick. It’s currently under construction in Shanghai. It’s not a project that could be designed by someone who likes trees.
Trees and other plants grown in elevated planters suffer the indignity of being part of a representation of trees. On the plus side, the plants look as if they might be left to form their own ecosystems without human interference apart from reticulation. By the look of it, it might not be a good time to be a mountain either.
This is the problem. Such projects offer some of the benefits of trees (and mountains) where previously there were none. However, my worry (on behalf of trees and mountains) is that should we become used to seeing privatised representations of Nature more often than the real thing, then these will become the real thing. And the preferred thing. To put it another way,
if a building can substitute for trees, then we won’t miss the land taken up by trees being used to build more tree substitutes. There’s no further need for forests.
This of course will only come about if we have a very narrow view of what a forest is and does. The objectification of trees and their subsequent mis-naming as vertical forests goes some way towards narrowing it. Forests are more than a lot of trees pleasant to look at. Trees are just one part of an ecosystem that involves climate, insects, soil and animals. This next image is an objectified tree that, if it had been planted in the ground and watered, might have helped enrich the soil and encourage the growth of less exotic plants requiring less water.
The only function of the objectified tree is to be ornamental. It’s a worry. Back in 2009 MVRDV were toying with the idea of fusing mountains, trees and buildings. This proposal is part of their China Hills project for Luizhou, in Guangxi, China. Trying to make buildings look like mountains has some inherent problems, not least of all the poor daylighting (for humans) because of the deep floorplates.
Their next proposal for Luizhou made the rounds not long after after. I don’t know if it was ever built but I can imagine it all to easily.
What is getting built in Luizhou is Liuzhou Forest City. It’s designed by Stefano Boeri Architetti. Clusters of buildings with mountain profiles from one or two directions looks like a typology we’ll be seeing more of.
So what’s next? MVRDV were about five years behind the curve when it came to building a greened building and are now looking at the retro-greenification of entire cities, as described in the cover story of the current issue of DOMUS.
The Green Dip project jointly conducted by WhyFactory [the research side of MVRDV] @TUDelft and IAAC in Barcelona calculated the environmental gains of having vegetation covering the surface area of entire cities. Doing this for Hong Kong would absorb 3,450,000 tonnes/year of CO2, produce 2,070,000 tonnes/year of O2, save €1.97 bil. in cooling, produce 7,160,000 MWh/year of energy and retain 489.62 hectolitres of H2O. Similar calculations were done for Sao Paulo and St Petersburg.
So there you have it. It’s all good news about easy-on-the-eye buildings, environmental gains and costs saved. Nobody’s saying that any forests need to destroyed but these fake forests are making it easier for us to think we’ll get along just fine in a world without them. To finish, here’s a current project by Jean Novel for Sao Paulo which, as you don’t need to be told, is in Brazil which, as I write, is burning.
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