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Living architecture: Growing buildings & bridges instead of building them

Can plants be shaped structurally to become living buildings, encasing entire facades that help carry a load and clean the air? Could buildings be planted and trimmed over time, adapting to the seasons and needs of those living within them?

Ferdinand Ludwig & Daniel Schönle have blended architecture and serious botany to design and build load-carrying structures built with trees, through their joint project Baubotanik (from bau, “building,” and botanik, “botany”).

When we visited Ferdinand and Daniel a few years ago in the Stuttgart area, Ferdinand —slightly long, straight blonde hair, with postgraduate looks— had finished his thesis about “growing architecture,” whereas Daniel —brown hair, sharp face and attire— had specialized, also studying architecture, in urban planning and regeneration. Both had the opportunity to put their ideas about “growing architecture” by encasing several cube-shaped public structures within a living tree facade.

A growing plane tree “cube” in Nagold, Germany

We visited them outside Stuttgart in October 2016; we were living in France back then and took advantage of our kids’ school autumn 2-week break to travel to Germany. Besides the highway and rest stops, we barely went through any town until our arrival in Nagold, 46 km southwest of Stuttgart, where Ludwig and Schoenle had half-built, half-grown their metal cube with a 10-meter length and high structure intermingled with a green facade. They had called it Plane Tree Cube (Platanenkubus in German) to honor the used species, London plane trees (Platanus hispanica).

The structure, designed as a contribution to the regional horticultural show in 2012, was designed so it would gradually “grow” to achieve its architectural maturity: “Young plane trees are arranged in plant containers on six levels. They form green walls around a space open to the sky.” But, in the course of time, the whole structure is behaving more like a tree, with the upper part of the space forming a thicker canopy, whereas the lower part has turned into a more transparent and knobby, with thicker trunks.

What looked like a living tower was located at a relatively vast park, with several areas performing different functions. Our first stop was an exceptionally well-furnished play area for children dominated by things to learn by doing and experimenting with, a big contrast with traditionally designed parks from the Paris area where we were living back then.

A new world of architectural possibilities

Our children studied a tubular structure designed to carry water and sand, and they rejoiced when they saw children of their age pumping water and working on a sophisticated sand structure. It didn’t take them much time to timidly join. Then we pointed at one structure to the side a couple of hundred meters from there, not far from an arched highway overpass crossing the valley. It didn’t take long to reach the place, so when Ferdinand Ludwig and Daniel Schönle joined us (previously, Ludwig had shown us a similar tree-made structure not far from there in the town of Ludwigsburg.

Ludwig and Schönle described their structure as a “pocket park.” Unlike structures made of mere inert materials, the Platanenkubus grows like a tree-building, performs the cycles of plants, and provides shelter from the elements in winter while allowing light in once the leaves have fallen, transforming into a cooler and inviting environment in the warmer part of the year, when the structure is covered by green Platanus leaves.

Living tree bridges have helped local populations in North East India overcome the endemic floods caused by the strong monsoons in the area

Ludwig, then a scientific coordinator of the Research Group Baubotanik at the University of Stuttgart and now a professor at the Technical University of Munich, described the technique of “plant addition” as a part of the ancient techniques of tree shaping used by people around the world for millennia to adapt plants for ornamental or utilitarian reasons, from the Japanese Bonsai to India’s Living Tree Bridges, a structural living marvel.

Plant addition: the old art of tree shaping

In “plant addition,” young plants are arranged above and adjacent to each other, so the connection stimulates their merge into a network-like plant structure. Only a few plants at the bottom of the structure are planted on the ground, whereas the plants above the structure use containers connected to an automated system providing water and nutrients. But, as the network develops, the plants in the ground grow more vigorously:

“Once the inosculations have developed, the artificially created plant structure can transport water and nutrients from the roots in the ground to the upmost leaves, and the roots of the container plants become obsolete. Step by step, these high-level roots can be cut off, the automated watering system can be removed, and, finally, the living structure becomes self-sufficient.”

Such a biological design relies on a process that also occurs in nature, though rare, called inosculation: when the friction between two trees causes contact underneath the bark, both entities respond by producing a callus tissue connecting them. The process is biologically like the artificial technique of grafting, used by humans since the Neolithic.

But the Baunotanik structure’s evolution doesn’t end here:

“Simultaneously, the secondary growth in circumference increases the strength of the plant structure and eventually it becomes self-supporting so that the scaffolding, initially required to support the containers and the young plants, can be removed.”

Next steps of the field of “living architecture”

Eventually, all the metal scaffolding can be removed, and the tree-shaping building becomes an entirely living structure. Could the Baubotanik “plant addition” technique give way to modern structures and infrastructures like India’s Living Root Bridges and ladders?

An example of botanic architecture that offers a lesson of resilience and symbiotic systems adapted to extreme-weather conditions

We asked Ludwig how big such structures could grow. To him, they could be as high as a mature tree of the chosen species (in the case of the Platanenkubus at Nagold, as high as a mature Platanus, or about 30 meters (100 feet tall):

“We made some design proposals even for whole streets where all the street trees are fused with the building in this way. So the people don’t live in a house, they live in a tree. For sure, there are some rooms behind there that are traditional in a way, but if you go out of the door, you stand in the tree, in the canopy.”

Ludwig and Schönle have evolved in their careers since our visit, though they keep collaborating through the Office for Living Architecture, OLA, along with Jakob Rauscher.

In the land of the Living Root Bridges (Northeastern India)

As cities try to combat traffic pollution and avoid the effects of more preeminent climate extremes, from heavy rain causing floods to the heat island effect, they have integrated plans to catalog, maintain, and expand trees and orchards in streets and parks, which contribute to control water runoff and extreme temperatures.

As the idealist architects-botanists at Baubotanik, the Khasi tribe of an isolated, heavily forested patch of Northeastern India have envisioned their own particular way to design living trees and ladders able to withstand the recurrent floods caused by the cyclical heavy rain brought by the monsoons. Their land registers the highest levels of precipitation on earth, so they learned to cope with the floodwaters cutting across their forest and isolating populations in seasonal islands. And, due to their geographical isolation from the rest of India, they kept their lifestyle and traditions during colonial times, and with them, the tradition of building/growing living bridges and ladders.

Architect Prabhat Dey Sawyan, born in the region, describes the landscape of his childhood as follows:

“Rolling hills, sparkling clean rivulets, crystal clear waters abounding in carp, and the skies brimming with a variety of birds singing their native tunes.”

Lo-TEK: Design By Radical Indigenism, Julia Watson, 2019 (p. 70)

Proven resilience of living bridges against the cyclical monsoons

Despite the force of the water, the Khasi don’t have to worry about their bridges, which are literally rooted to the ground and guided over generations to connect riverine corridors of the Jaintia Hills district (with one elevation going from 1425 meters to almost 2000 meters, from 4675 to 6500 feet).

The Khasis mythology taps into their symbiotic relation with several species of plants and trees, especially the Ficus elastica (rubber fig tree), the species that formed a mythical bridge called the jingkieng ksiar or “golden ladder to heaven” connecting their land with a place in the clouds (bneng or “heaven”). To the Khasis, the rubber fig tree is their symbolic stairway to heaven but also the utilitarian tool to guarantee the transit between populations during the long rainy season.

Living root bridges are still used and maintained across the Jaintia Hills

The living trees from the Jaintia Hills didn’t pop up at random: if the Way of Saint James in Spain connected Christian pilgrims to Santiago de Compostela, where it was believed that Saint James the Apostle was buried, securing Northern Spain for Christendom during the convoluted Middle Ages, the King’s Way in the Jaintia Hills region connected the Khasis villages to the city of Shillong, where the local betel nut trade was located and locals were exposed to peoples and products from Northen India, Indochina, and the Himalayas.

Prabhat Dey Sawyan answers to the question of why the Khasi decided to “grow” instead of “make” their own bridges:

“The living root bridges are built along the natural routes connecting two villages. In the absence of any means to lift and carry heavy stone slabs to suspend them across river and streams, they are left with no option but to turn to mother nature in their endeavour to cross to the other side. The rubber tree (Ficus elastica) growing in the region beyond Cherrapunjee (Sohra) provided the natural solution. Timber would not have been able to withstand the ravages of the harsh monsoons and the scourge of termites and pests.”

Lo-TEK: Design by Radical Indigenism, Julia Watson, 2019 (p. 70)

The bridges along the King’s Way

The King’s Way remained operative throughout the mountains and despite the monsoons thanks to a network of hundreds of living tree bridges. They had been built in four different stages of development with different species: first, rubber trees grown around boulders develop their primary root system attached to each river shore.

The rubber tree roots are oriented towards boulders on the other shore, often over riverbeds 10 to 30 meters wide. The secondary root system of the Ficus elastica secures the connection of both shores, establishing the footing of the living root bridge.

In a second phase, betel nut trunks are used across the new bridge to form a root-guidance system. Once the rubber fig tree’s secondary root system and the new-guidance system intermingle into a flexible, alive patchwork, the bridge accommodates round river boulders that the root system will secure in their place over time, creating a sturdy path for people and load animals use. The newly built living root bridge is now an integrated infrastructure that requires little maintenance and is capable of holding in place even when storms cause flash floods and strong currents down the myriad of monsoon riverbeds.

Lessons for a world with more and more intense extreme-weather events

New York-based researcher and landscape designer Julia Watson, author of Lo-TEK: Design By Radical Indigenism, the living root bridges and root ladders of the Khasis are one ancient example to show contemporary society how to build “living architecture” for the future. They are responsive, productive, adaptable, and resilient:

“Implementing biodiversity as a building block, their use [by the Khasis] of living trees as a building material has allowed this infrastructure to increase in strength and size over time, minimally disrupt natural cycles, and increase overall biodiversity, all while responding to environmental pressures such as decomposition and flooding.”

Lo-TEK: Design by Radical Indigenism, Julia Watson, 2019 (p. 63)

Living trees are an ancient, effective and economic response to extreme weather conditions. It shows how living trees become stronger over time thanks to their adaptation to monsoon floods, growing higher and building stronger roots. Studies show their efficient load-bearing ability, which would be unmatched by a traditional, heavier, inert structure.

“In cities where flooding and sea level rise is inevitable, and infrastructures are continually failing, making populations vulnerable, these examples of man and nature working on symbiosis offer new directions for designers and engineers.”

Lo-TEK: Design by Radical Indigenism, Julia Watson, 2019 (p. 63)