How are Living Root Bridges Made?

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.

Active community maintenance on a root bridge

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

Inosculation of young roots. These strands were twisted together by hand and then merged with one another naturally. By encouraging this process, Khasi increase the strength of living root bridges

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.

The gallery above shows a living root bridge where virtually all of the recent maintenance has been in the form of roots that were manipulated by hand.

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.  

This is a damaged living root bridge undergoing significant repairs, most of which are in the form of aerial roots simply being tied together and readjusted (though some bamboo is also used). I visited the same bridge a year later and found many of the manipulated roots still in place

Here, very young ficus elastica roots have been wound together by hand in the hope that they will combine and one day be able to hold the weight of a person. The photo is from the span of a living root bridge near the village of Rangthylliang

ROOT BRIDGE TRAINING USING WOOD OR BAMBOO SCAFFOLDING

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Work being done on a root bridge in development. Here, an extensive scaffold made of bamboo and wood has been built around a few already established roots. The person in the foreground is guiding very young strands around the outside of the scaffold. When this photo was taken the bridge was usable, though much of the stress was taken by the scaffold rather than the ficus roots. It has since developed significantly

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.

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Here, a new span for a pre-existing living root bridge is being generated. The two straight lines near the top of the photo are where young roots are being guided along bamboo poles. The structure has developed significantly since this photo was taken
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This is a picture of the same bridge, taken from above the span that is being generated. Here, you can see how the new span is being trained by wrapping young roots around the sticks and bamboo poles

ROOT BRIDGE TRAINING USING HOLLOWED OUT ARECA PALM TRUNKS

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Ficus elastica roots that have been trained through an areca palm trunk in order to develop a living root bridge. Here, one can see how the decomposition of the areca trunk provides the roots with nutrients

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. 

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Ficus elastica roots being directed through a hollowed-out areca palm
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A view of the scaffold being used in the creation of a new span on the famous Double Decker root bridge. Note the variety of materials being employed here, including wood, steel wire, and bamboo strips

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.

A new railing being grown on a tourist-frequented root bridge near the village of Nongthymmai using ficus elastica roots directed through an areca palm trunk. Wires and bamboo strips are also being used
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Another view of the same new railing (the structure at the upper right) that was being generated as of 2016
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Young ficus elastica roots being trained through a hollow areca trunk, near Mynteng Village

ROOT BRIDGE TRAINING USING STEEL CABLES AND WIRES

Sometime ficus roots are grown around already fixed steel cables. This is part of a hybrid structure composed of roots, steel, and concrete

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.

The Hybrid of Nongriat

In some examples of recently damaged living root bridges, steel elements have been used to repair and help regenerate the structure.

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This is part of a large, though badly damaged, living root bridge in the vicinity of Nongthymmai village. Here, a large part of the root bridge has been removed and replaced with steel wire in order to provide a functional railing. At the same time, an attempt is being made to create a new “living” railing, using the areca palm method

THE GREAT BRIDGE OF MAWKYRNOT: A CASE STUDY

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The Great Bridge of Mawkyrnot as it appeared in 2015

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.

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A friend poses on the walkway of The Great Bridge of Mawkyrnot as it appeared in 2015. The walkway was then made mostly from bamboo, with one large ficus elastica root running under it
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As of 2016, the bridge had been modified. Here, you can see many roots running along the structure, several of which had been placed not long before this picture was taken
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A close up of the walkway as it appeared in 2016. Given its thickness, it seems that the large root in the center of the photo was growing across the stream (visible to the left of the picture) for a long time. Note the strands that have been guided across the structure by hand
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Here, some young roots are being left to develop on their own, while one is being run through an areca palm trunk. On this particular living root bridge, the areca palms that are being used to guide the young roots are also being employed as handrails
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While their use is limited, the Great Bridge of Mawkyrnot is also being developed with the help of conventional elements such as steel wire and concrete. Note also the use of bamboo and wood in the scaffolding behind the concrete post
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Note the thin aerial roots coming in from the right side of this photo which have been tied onto the structure to increase stability

CONCLUSION

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.

Root bridge maintenance

*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.

Click here for a list of posts on living root bridges.

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