Indigenous ingenuity: India’s living bridges inspire architects

Covered with thick subtropical forests and streaked with streams and rivers, the hilly state of Meghalaya in India’s northeastern corner is one of the wettest places on the planet. During the monsoon season, torrential rains turn docile rivers into raging waterways, and people rely on centuries-old bridges to access farms, schools, and markets. 

But these aren’t typical overpasses made of wood or steel – the bridges are alive. 

For hundreds of years, the Khasis of Meghalaya have manipulated the aerial roots of the rubber fig tree (Ficus elastica) to build sturdy bridges, known in the Khasi language as jingkieng jri. There are at least 150 such bridges in Meghalaya, according to Morningstar Khongthaw, who works to preserve and educate the public about the community’s architectural traditions. The figure includes the famous double-decker living root bridge of Nongriat village, which locals estimate is about 250 years old. Mr. Khongthaw’s village, Rangthylliang, has 20 living root bridges. “The oldest one is about 700 years old,” he says, with great pride.

Today, the jingkieng jri are not only a big tourist draw, but also an important proof of concept for engineers and designers interested in practicing living architecture. Integrating plants into architectural design lessens the need for harmful construction materials and promotes biodiversity, but it can also take generations to test and develop the right building methods. Bioengineers from around the world are studying the living root bridges in the hopes of applying aspects of the Khasi tradition to projects in their own countries.

“The Khasis have a brilliant understanding of architectural engineering, totally different from the western way,” says Ferdinand Ludwig, professor of green technologies in landscape architecture at the Technical University of Munich. “Their way of thinking forms the conceptual base of a new way of architecture and engineering that we urgently need to cope with climate change.”

Ancient bioengineering

“There are different ways of designing, building, and growing a living root bridge,” says Mr. Khongthaw. The most popular model of construction, and the fastest, involves the creation of a bamboo framework, over which the roots of a nearby rubber fig tree are pulled and intertwined, until the roots reach the opposite bank. The bamboo framework itself serves as a temporary bridge while the living root structure takes shape. Over time, the bamboo rots away while the roots grow and merge together, making the structure sturdier and more stable. 

The time required to reach the first functional stage – when the bridge is strong enough to hold about 500 pounds, or roughly three people with loaded baskets – depends on the required length of the bridge. Mr. Khongthaw says a bridge crossing a stream would be about the length of a school bus, and take nearly 20 years to become functional, whereas a bridge across a river would take 70-80 years. In places where there are no rubber fig trees nearby, villagers must first plant a sapling on the river bank and wait 10-15 years for the aerial roots to appear before building the bamboo framework. 

In all stages of their development, the bridges require regular maintenance. This happens in monsoon season when the roots are more pliable. “Everyone in my village takes part in maintaining the bridges,” says Mr. Khongthaw. “Whoever crosses the bridge, spends five or 10 minutes working on the roots to make the structure stronger.”

In the past, the work of constructing and maintaining bridges was done by men. But that is changing. “Nowadays, women are also involved,” says Mr. Khongthaw.

In addition to bridges, the Khasis construct cliffside ladders, tree platforms, swings, and tunnels using traditional techniques passed down orally from one generation to the next. Now, the Khasis are sharing their knowledge with the rest of the world.

Global applications

In Germany, Professor Ludwig has been studying examples of living architecture from around the world for nearly two decades. He has designed and overseen the construction of several structures that integrate plants, including a footbridge that uses living willow plants as the sole supports.

Professor Ludwig first learned of the living root bridges of Meghalaya in 2009, via a documentary, and was struck by the Khasi approach to building. “They do not prescribe the structure itself. They only prescribe the aim,” he says. “They want to go from A to B in a safe and comfortable way. They plant a tree and manipulate the growth of the roots in a direction that is beneficial to them.” 

One of his students at the Technical University of Munich, Wilfrid Middleton, is studying Meghalaya’s living root bridges as an example of regenerative design – an increasingly popular concept wherein structures are not just sustainable (built with minimal and efficient use of resources) but they also replenish the resources required for their functioning and enrich their surroundings, thus having a net-positive effect on the environment. In cities, living structures like the footbridge designed by Professor Ludwig can help sequester carbon, create a cooling effect, and provide a habitat to birds and other urban wildlife. Manipulating ficus plants or comparable species could open up “new solutions for [greening] construction in densely populated urban areas,” Professor Ludwig adds.

Mr. Middleton has visited 70 jingkieng jri so far, and with the consent of the village elders, he photographs the bridges to create precise 3D models. “Each year, as the bridge grows and changes, we are able to capture its incredibly complex structure,” he says. “We are trying to learn from the Khasis.”

Preserving Meghalaya’s bridges

While there is increasing international appreciation of the living root bridges, back in Meghalaya, Mr. Khongthaw says many villagers aspire for a modern lifestyle, complete with concrete houses and bridges. Worried that traditional Khasi knowledge may feel irrelevant to younger generations, Mr. Khongthaw founded the Living Bridge Initiative in 2016, with the objective of preserving, protecting, and increasing the number of living root bridges. He regularly visits educational institutions to speak about his work.

“These bridges, which our elders have worked on for so many years, are being forgotten,” he says. “I wanted to start something to recognize their efforts.”

Mr. Khongthaw has also started a sapling center to address the shortage of rubber fig saplings, which are not easy to find in the forest. The biggest threat to these ancient bridges, however, are the development projects in their vicinity. 

Byron Nongbri runs a homestay with his wife, near the famous double-decker bridge in Nongriat village. In 2016, he participated in stopping a road project that would have led to a flood of tourists in the area. Now he is worried about a limestone mining project underway barely 3 miles from his village. “It will surely harm my paradise,” says the father of five.

Meanwhile, Mr. Khongthaw finds hope in building new bridges, and honoring the wisdom and ingenuity of his ancestors. He was recently involved with the construction of seven bamboo bridges, each of which will be used as the framework for a new living root bridge, to be shaped and maintained by future generations. 

“Our knowledge should be recognized not only in Meghalaya but everywhere,” he says.