HOW ARE LIVING ROOT BRIDGES MADE?*
The Khasi people of Northeast India create living root bridges using the pliable aerial roots of the ficus elastica species of fig tree. The natural growth of the roots is harnessed to gradually form an architectural structure, using both the root’s tendency to anchor themselves to other objects and their propensity to combine with each other via the process of Inosculation. This can take many years, though the exact amount of time necessary for a root bridge to become functional is dependent on several local factors such as how healthy the tree is, how flood-prone the stream the bridge crosses is, how much the people crossing the bridge mind wobbly roots, and the degree of community involvement there is in developing the structure.
There are several methods Khasis use to generate living root bridges, and these vary from example to example and from area to area. However, it is important to note that in all instances the creation of a living root bridge is very much a long-term, social, process, with additions and improvements being made even generations after the initial planters have died. Following a root bridge’s initial period of development, it is reinforced when pedestrians using the bridge periodically rearrange the naturally growing roots found on the span in an architecturally beneficial way. Because of this, root bridges are continual works in progress. A root bridge that’s over a hundred years old is still part of a living, changing, organism.
I’ve arranged the methods Khasis use to create living root bridges into four broad categories. Bear in mind that the development of a single bridge might involve several methods.
The methods are:
a): Root bridge training without scaffolding.
b): Root bridge training using bamboo or wood scaffolding.
c): Root bridge training using hollowed out areca palm trunks.
d): Root bridge training using steel wire.
ROOT BRIDGE TRAINING WITHOUT SCAFFOLDING
Almost all living root bridges that I’ve observed which were still being actively maintained showed signs of roots that had been manipulated by hand to improve their strength and stability. These improvements often took the simple form of a few individual roots that had been wrapped around each other, tied to trees, or attached to the opposite bank of a stream. I’m told that these spur of the moment improvements are usually done by agriculturalists working in the jungle who regularly use living root bridges to reach their crops and so take it upon themselves to improve the structures over time. The Khasis understand that if the individual ficus elastica roots of a given root bridge are tied or twisted together they will gradually merge, forming a stronger overall structure.
While the methods used in the initial generation of many older bridges is often not clear, I have seen examples where no scaffolding was ever used, and where the structure was formed entirely by hand.
The northern span of the double root bridge pictured above (the side without any rocks) was generated entirely without the use of a scaffold, and all maintenance and further development has been done by hand. The span was first brought into existence by the man in the red shirt you can see working in the pictures.
Simply tying and twisting roots together is the most common form of maintenance one sees being administered on living root bridges, even those that have undergone significant damage.
ROOT BRIDGE TRAINING USING WOOD OR BAMBOO SCAFFOLDING
Many root bridges are created using scaffolds made of wood or bamboo, materials which can be found virtually anywhere in southern Meghalaya.
In these instances, young ficus elastica roots can often be seen twisted around bamboo poles, while sticks and tree trunks are used to increase the stability of a temporary bridge/scaffold. While these materials rot quickly in the hot, humid, climate of southern Meghalaya, given their ubiquity, they can be easily replaced from season to season.
The roots, providing the tree they are a part of remains healthy, gradually become stronger and thicker, and with many adjustments to the scaffold over time, slowly develop into a functional living root bridge. Once the roots can be safely walked upon, the scaffolding is no longer necessary. However, additions and repairs to already functioning root bridges are still sometimes made by guiding aerial roots along the outsides of sticks, tree trunks, or bamboo poles.
This method appears to be practiced throughout the area where root bridges are found. In some areas, root bridges are also created using a method employing hollowed out areca palm trunks (see the next section). However, in areas where areca palms do not grow in abundance, the use of wood or bamboo scaffolding is simply more practical.
ROOT BRIDGE TRAINING USING HOLLOWED OUT ARECA PALM TRUNKS
Another method for creating living root bridges is to use the hollowed-out trunks of areca palms. These are placed across streams and rivers, and then young ficus elastica roots are guided through them. The trunks serve to direct the roots, to protect them, and also to provide the roots with nutrients as the trunks decompose. In this way, a strand guided across a stream using an areca trunk has a solid chance of growing thick enough to become a useful part of an architectural structure.
This method is practiced around the village perhaps best known for its living root bridges: Nongriat. This is a tourist friendly area, and so the use of areca palm trunks can be easily observed here, and also in the nearby settlements of Nongthymmai and Mynteng.
ROOT BRIDGE TRAINING USING STEEL CABLES AND WIRES
Though conventional materials such as steel cables and wires have often come to replace root bridges entirely, in a few places they have been incorporated into living structures.
Near the village of Nongriat, there is a particularly interesting example of a “hybrid” structure, where ficus elastica roots have been trained across a pre-existing steel wire bridge. Here, the functional, conventional, structure doubles as a scaffold on which to develop a root bridge. As the roots have grown and gained in strength, the steel wires have become effectively redundant, and will be allowed to rust away sometime in the future. In this way, the long phase of root bridge development during which the structure is not usable because it is still too young and its roots are too thin has effectively been bypassed.
In some examples of recently damaged living root bridges, steel elements have been used to repair and help regenerate the structure.
THE GREAT BRIDGE OF MAWKYRNOT: A CASE STUDY
The Great Bridge of Mawkyrnot (my nomenclature), located a few kilometers from the mid-sized town of Pynursla, is an unusually impressive root bridge which, though clearly quite old, has nonetheless been developed extensively in the last few years by a local tourism society. Examples of all four of the training methods listed above are present at this bridge, which allows it to serve as a sort of “showcase” for all of the different ways in which living architecture can be generated.
It’s important to remember that the Khasis who invented living architecture did so without training. They weren’t professional engineers, and they used no blueprints. To them, root bridges were a simple, low-cost yet long-lasting solution to a very basic problem.
In a way, this makes the bridges all the more exceptional in that they are instances of functional architecture that have often seen hundreds of years of service, are in some cases stronger now than ever before, are objects of incredible aesthetic value, and yet they are products of, for lack of a better term, “amateur” architects. What this means is that the basic idea of a living root bridge, despite seeming so unusual and ingenious, is nonetheless something that could be easily transplanted to other contexts. Various kinds of banyan trees can grow in many different environments, from urban areas in Bangladesh, to southern Florida, to indoor gardens anywhere in the world.
*Note: This post is a slightly reworked and updated version of a page from a previous incarnation of my blog on Khasi living architecture from 2017, which was the source for much of the Wikipedia article on the subject.
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