For a project called Bosco Verticale (or Vertical Forest), Stefano Boeri proposed two 27-story buildings to be the world’s first ‘vertical forest’ to be completed in Milan later this year, has grown into many people's blueprint for what they expect to see in cities in 50 years, sparking the debate over this notion [52]. Tim De Chant, a plant physiologist, environmental researcher and critic, was among the first to raise this question in his article “Can we please stop drawing trees on top of skyscrapers?”, triggering a broader debate among critics and architects [46]. De Chant protests against the trend of festooning skyscrapers with trees: “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” [46]. He points out that the trees are not adapted to the diverse range of conditions they would likely be exposed to on the side of a skyscraper [46]. Apart from logistical concerns such as the constant attention those trees require, there is the issue of prevailing winds that face trees in elevation that could lead to trunks buckling and bowing away [46]. Therefore, tall and graceful trees which are often drawn in architectural drawings and renderings are unlikely to survive in real-life conditions [46]. Robert Krulwich, a former science and economics correspondent, directly responds to De Chant’s arguments in his article “Trees On Top Of Skyscrapers? Yes! Yes, Say I. No! No, Says Tim.”[50] Krulwich’s position is made clear from his title and introduction: “I love this…Milan is a very polluted town; these trees will cleanse the air… I hope [De Chant]'s wrong” [50]. He proceeds to explain how the project architects have consulted botanists and were careful enough to select plants that would withstand the altitude conditions [50]. Krulwich argues that the plants are more likely to survive, since in his opinion the towers that rise up to about 111 meters are “tall, but not crazy tall” [50]. Nevertheless, he acknowledges De Chant’s concerns about wind forces and extreme temperatures at such altitudes [50]. Interestingly, he admits a margin of error, accepting that mistakes are bound to be made in new experiences but could lead to a future success, drawing hope from the Finger Mountains in China as a prime example of plant life at high altitudes [50]. Nevertheless, as Maathai reminds us, it is important to keep into consideration that nature is already wounded, thus, we should avoid any unnecessary actions in our process that may take effect on the environment [30]. Further, trees on skyscrapers lose their spiritual role; they are now attached to something rather that rooted in the ground. One begins to wonder whether they truly serve their purpose or are another tool of ornamentation. In the interior of the Dubai International Airport (picture below), we experience a space flanked by tall gracious palm trees, whose vaulting space extends a feeling of exhilaration and openness that encourages a sense of spirituality. Yet, on a closer look at the trees and the planters, we discover that the trees are not real. An argument may be that they would not survive the lower light levels indoors, but could the design overcome that? Surely, Dubai, and the UAE in general, have led several campaigns to reduce their carbon footprint and plant trees, and there is no denying that there have been a generous drive in doing so [6,8,14,19,20]. However, there is a gap to be filled. While family homes and villas might cover the introduction of trees and vegetation into private architecture through landscaping, it is still an area to be explored in public structures and skyscrapers.
In response to Krulwich, De Chant returns with another article, “More reasons to stop putting trees on skyscraper”, in which he shares his insights and concerns [47]. He explains how trees on skyscrapers serve as a distraction from the bigger picture: deforestation and uncontrolled development [47]. In addition, he points out that these trees are restricted to the rich and the tenants, as opposed to what Maathai hopes for, “creating a clean and healthy environment that my benefit everyone rather than only individuals”[30,47]. Further, in the Bosco Verticale, when considering the weights of the heavy trees, the dirt and its moisture content, the watering systems to keep the trees alive, and the deep planters, they all add up to the structural materials and supports if the building, thereby, increasing costs [47]. This calculates to an expected amount of $85 million plus $4.25 million to put 25 acres of forest – a hectare- on the side of a building, without considering the maintenance costs [47]. Now, assuming the $4.25 million was taken to revive the region’s natural habitat, with the top cost of around $2,000 per acre (U.S. national forests), an area of 2,215 acres- about 860 hectares- of forest land could be restored [47]. With this calculation, De Chant suggests that reforestation is perhaps a more convenient alternative, since it could result in 860 times more forest than those that are on the side of Bosco Verticale, and up to 8,600 times more if the cost per acre was about $200 (the minimum cost) [47]. Interestingly, there has been global efforts by economically developed countries to paying for their carbon footprint by funding reforestation projects in developing countries and also Nicaragua, Haiti and the Solomon Islands [38-43]. Next, he brings our attention to the replacement of trees, “Given that more than 50 percent of street trees, which are exposed to more benign conditions, die after just 10 years”, skyscrapers would need an overhaul every 10 years, assuming the trees survive for a similar period of time [47]. Instead of plastering trees on skyscrapers, De Chant calls us to focus on preserving and restoring sites that desperately need, or already have, trees [47]. Summing up, as much as De Chant yearns for sustainable and successful skyscrapers, he expresses:
“Plant physiology tells me… if they do survive, [the trees] will require constant and costly maintenance throughout their short, brutal lives. Finance tells me that the money required to afforest a building would be more effectively used for restoration and preservation. And my gut tells me there are more equitable ways to give people trees, not just to those who can afford it” [47].
Several architectural critics and editors, such as Vanessa Quirk, Andrew Sullivan, Russell Brandom, Francie Diep, Lloyd Alter and Annalee Newitz, support De Chant’s position [44,45,48,52,53,56]. Others, such as Joe Romm and Zak Stone welcome the project’s concept and its possible benefits, with anticipation towards the project’s completion as proof to De Chant’s theory [54,55]. Despite affirming De Chant’s arguments that money could be better-spent preserving ground-level green spaces in “No, Architects, You Can't Plant Trees On Top Of Skyscrapers”, Diep shares Krulwich’s opinion that trees on skyscrapers could lead up to growing the kinds of trees that have evolved for conditions around sea cliffs and mountaintops [48]. On the other hand, Lloyd Alter, a green architect, developer and inventor, adds to Tim De Chant’s list another concern: the size of the planters [44]. In his article, “Are architects going overboard with the trees on buildings?”, he attests that the roots of city trees have enough trouble finding enough space at ground level in sidewalk planters [44]. Given the fact that the American Standard for Nursery Stock suggests that a 91 cm planter can hold a tree with a maximum caliper of 9 cm, Alter reveals that trees in renderings as seen from a project by Studio Nicoletti are “just unrealistic and impossible…As I noted about this dead project at the time” [44]. On another project by architect Édouard François, executed in 2004, known as Flower Tower, Alter sets another example. Alter reveals that in a visit to the project in 2011, Invisible Paris discovered that "The bamboo is not in perfect condition, but certainly in a better state than could have been expected", as it has grown out to look entirely dissimilar from when it was first planted, and it seemed that some of it was struggling [44]. This illustrates the magnitude of the concerns that Alter share with De Chant since the plants discussed were just bamboo, and not big trees.
3. CONCLUSION
In conclusion, modern solutions to introducing nature into industrial settings, such as planting trees on skyscrapers and having sky gardens in buildings, requires careful and thorough study, planning and execution. Tim De Chante’s arguments set forth the deception of renderings and calls for a better understanding of the practicality of concepts and their chances of working in the real world. This could be improved through interdisciplinary collaboration; architects, engineers, botanists and contractors should share their experiences and knowledge to bridge the gaps in other fields, and reach towards a refined, effective solution. Similarly, Robert Krulwich’s message invites the trial-and-error dialogue that could result from such experiments. However as De Chante’s stresses, they should not be at the expense of the common good as an ‘illusion’ of sustainability. Finally, even though if the critics disagree in opinions and positions, they can all agree on one thing: an effective, practical, and collaborative approach is a step closer to achieving a sustainable Maathai utopia.
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Gaser Mohamed is an Egyptian student in his senior year at the American University of Sharjah, College of Architecture. He is interested in expanding his knowledge in sustainable design, game design, as well as exploring upcoming virtual reality/ virtual environment tools. He is passionate about drawing and is currently working on illustrations for a comic book series.
