We have relied on concrete, cement, asphalt and other chemical based composites to construct our buildings that it has done substantial damage to our environment, in terms of global warming carbon emissions etc.
This lead architects and engineers to think of alternative methods of construction, that gave rise to the term – Green Building. Though the concept is at a very nascent stage and its application is also quite limited in the real world, but this realm of architecture is gathering some serious response from the international community; to the extent that various research teams are studying ancient and traditional methods and techniques of construction using natural materials.
One such research study was conducted by Prof. Ferdinand Ludwig of the Technical University of Munich (TUM). He research and investigation was done in North Eastern Parts of India particularly Meghalaya. He investigated that this region has quite dense and humid forests and during monsoons that mountain streams in such areas convert into swollen rivers. So typical steel & concrete bridge will not work in such a scenario, not would wooden bridges last long. So the local communities – Khasi and Jaintia – have built their bridges using living aerial roots of the Indian rubber tree Ficus elastica. “Stable bridges like these, made of closely intertwined roots, can reach more than 50 meters in length and exist for several hundred years,” says Prof. Ferdinand Ludwig.
Prof. Ludwig has analyzed 74 such living bridges and conducted interviews with the bridge builders in order to understand the building process. The researchers took several thousand photographs, which they used to create 3-D models, providing insight into the complex root structure.
The building process starts with plating a seedling of Ficus elastica on the bank of river. As the plant grows, it developed aerial roots, which are then wound onto a frame of bamboo stems and directed horizontally over the river. Once the roots grow up to the other bank of the river, they are implanted. These further develop smaller daughter roots, which are directed to the bank again. So because of this process of growth and winding, the roots of the Ficus elastica form highly complex structures which create stable, safe bridges. Newly growing roots are integrated in the existing structure repeatedly.
The properties of the Ficus elastica play an important role. The roots react to mechanical loads with secondary root growth. In addition, the aerial roots are capable of forming inosculations. This is a process in which trunks, branches and roots of one plant grow into the structure of a second plant. Possible injuries result in inosculation and callus formation, a process also familiar from wound healing of trees. The bridges are made and maintained by individuals, families or by communities that include several villages that use the bridge.
However this is a long process which takes decades and run through generation. But given the environmental damage we have done, it is time we learn such techniques from different inhabitants and imbibe them in our modern architectural practices. This would not just make our cities cooler and carbon free but will also lead to better understanding of our ancestors’ lives.