‘The Living Root Bridge’ – A bioengineering paragon

“Bridge”. What comes to your mind first when you hear the word ‘bridge’? Maybe the Golden Gate Bridge, the Sydney Harbour bridge or our very own Pamban bridge or the Howrah bridge, or any other bridge that you cross more often, right? I hope you are not thinking about cards on these quarantine days. Jokes apart, bridges are truly architectural wonders with magnificent designs to withstand the weight and natural adversities. But, today I want to talk about a different kind of bridge, ‘the living root bridge’! Last December I went to Meghalaya and there I first saw the living root bridge. From then on I became interested in this bioengineering marvel and today I want to share with you some astounding facts.

“In the wettest place in the world, you won’t cross bridges that were built. You’ll cross bridges that were grown.”

A living root bridge is a type of simple suspension formed of living plant roots by tree shaping. Though they are living root bridges, they are not naturally formed, they are formed of aerial roots of rubber fig trees (Ficus elasticia) which are trained by the Khasi and Jaintia peoples of the Shillong pleatue. The living root bridges take 15 to 30 years to be built. So, why these bridges if they take this long to form? Why can’t simple bamboo bridges be used instead?

Why living root bridges?

Well, the answer is quite simple. Meghalaya is one of the wettest states of India. During the monsoons from June to September, rivers in Meghalaya cause terrible floods. Historically, the Khasi people built bridges out of bamboos. But those could not withstand the frequent floods and would decay more often. Now necessity is the mother of invention. The inhabitants noticed that the tree Ficus elastica stands strong in those regions in spite of flash floods and storms. With the help of an extensive network of secondary roots, these trees perched atop boulders, slopes, and even on the rivers. Thus they got the idea of building bridges with the help of the roots of these trees and thus the idea of building the root bridge got implanted.

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How were the bridges built?

Now comes the most interesting part, how the bridges were built? The Khasi and Jaintia people adopted techniques to ‘train’ the roots in such a way that they would grow and eventually cross the river. Initially, those people used to manipulate the young and tender roots with their hands. Later on, they used other skillful and efficient procedures. The different techniques adopted to build the root bridges over the year are beautifully given in Wikipedia and here I am presenting it.

“Root bridges are also commonly formed by training young Ficus elastica roots over scaffolds made from wood or bamboo, materials which are abundant in Northeast India. In these instances, the roots are wrapped around the outside of the perishable material. The scaffolds may be replaced many times over the years as the root bridge becomes stronger.

Some living root bridges are grown by training young Ficus elastica roots through the hollowed-out trunks of Areca nut palms. The pliable tree roots are made to grow through betel tree trunks which have been placed across rivers and streams until the figs’ roots attach themselves to the other side. The trunks serve to guide the roots, to protect them, and to provide them with nutrients as they decay.

Root bridges can also be trained by guiding the young roots of Ficus elastica trees across conventional structures, such as already existing steel wire suspension bridges. As the structure is used as a scaffold is already functional, the problem of the length of time it takes for a root bridge to become functional is here essentially bypassed; the conventional structure can be used until the more sustainable root bridge is sufficiently strong.”

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Fascinating Facts about the root bridges

The roots bridges vary hugely in shapes and sizes. Some of them stretch 170 feet while some hang 80 feet above the running streams. The root bridges have a long lifespan, they live and grow as long as the tree they are part of, lives. Though they take a while to be functional, once they become established, they are strong enough to withstand the weight of 50 or more people at a time. As the bridges grow throughout their life, they gain strength over time and as per sources “some of the ancient root bridges used daily by the people of the villages around Cherrapunji may be well over 500 years old.”

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Double-decker living root bridge!

You will be fascinated to know that, there is also a double-decker living root bridge! They are very rare as most living root bridges have a single span. They are built in such a way that two parallel spans are formed, one stacked over the other. These give greater strength, but they are very difficult to build. One such double-decker bridge is the “Umshiang Double-Decker Root Bridge” which is also a famous trekking route!

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It’s high time to raise the awareness

It is very sad that the culture of building new living bridges slowly fading out. People have moved to cities with time and there are very few people left in those villages who really need the root bridges. The existing root bridges are also not properly preserved. However, in around 2004, they have gained attraction from people all over the world. Tourists come to visit the root bridges regularly. Due to this, the local inhabitants are hugely benefitted economically. Thus many existing root bridges are properly taken care of. And more importantly, some new root bridges are also under construction. As per sources ” In the village of Rangthylliang, an entirely new bridge is being grown using a bamboo and wood scaffold, and at the double-decker site in Nongriat, a new, third span is currently being grown above the other two and should be ready for use within a decade.”

By Soumyanil Adhikary, Department of Chemistry, IISER Bhopal.

References:

  1. https://www.atlasobscura.com/places/root-bridges-cherrapungee
  2. https://en.m.wikipedia.org/wiki/Living_root_bridge
  3. https://www.google.com/amp/s/api.nationalgeographic.com/distribution/public/amp/travel/destinations/asia/india/living-root-bridges-clean-village-mwalynnong-india
  4. https://www.google.com/amp/s/www.insider.com/india-living-root-bridges-photos-2019-1%3famp.

Image source: Author himself, Outlook India.


Other articles by the author:

About the author:

Soumyanil is a 3rd-year BS-MS student at IISER Bhopal, pursuing Chemistry major. Other than studies he likes playing guitar and read novels. He loves traveling and has traveled a lot; recently he has done his first trek. Besides he takes interest in cooking and needless to say he is a big foodie too. He is a big fan of football and cricket as well. Also, He is associated with The Qrius Rhino!

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