Living root bridges are an ingenious type of suspension bridge shaped from plant roots. They are common in the southern part of the Indian state of Meghalaya (in the northeast of the country), home for some of the wettest locations on Earth.

The Khasi and Jaintia communities who inhabit the region needed a low-cost way to cross the valleys and gorges in the rainforest during monsoon season. Living root bridges are sturdy and easy to build—albeit time-consuming—and apparently they withstand flash flooding and storm surges quite well.

The building process is described by Zinara Rathnayake for BBC Future as follows:

“Building these bridges takes decades of work. It begins with planting a sapling of Ficus elastica – a tree that grows abundantly in the subtropical terrain of Meghalaya – in a good crossing place along the riverbank. First the trees develop large buttressing roots and then, after about a decade, the maturing trees sprout secondary aerial roots from further up. These aerial roots have a degree of elasticity, and tend to join and grow together to form stable structures.

“In a method perfected over centuries, the Khasi bridge builders weave aerial roots onto a bamboo or another wooden scaffolding, wheedle them across the river and finally implant them on the opposite bank. Over time, the roots shorten, thicken and produce offshoots called daughter roots, which are also trained over the river. The builders intertwine these roots with one another or with branches and trunks of the same or another fig tree. They merge by a process called anastomosis – where branching systems like leaf vessels, tendrils and aerial roots naturally fuse together – and weave into a dense frame-like structure. Sometimes, the Khasi builders use stones to cover the gaps in root structures. This network of roots matures over time to bear loads; some bridges can hold up to 50 people at once.”

Despite not having the capacity of bridges built entirely from man-made materials, the capabilities of living root bridges are nothing to sneeze at in the kinds of difficult terrains they’re used for. For example, the longest living root bridge is the Rangthylliang bridge at 50+ meters long. That kind of length makes for plenty of potential for similar live-plant-based bridges in speculative gaming campaigns or stories, from ad hoc methods of river crossing for an army or a group of refugees (with the help of plant-growth spells) to permanent structures for local communities.

Living bridges can also last for many hundreds of years in ideal conditions. Even if the oldest currently existing bridges were “merely” from the 1800s, it’s clear that that kind of longevity wouldn’t be possible without community building and traditions passed on and cherished. I.e., the structures solve a concrete problem in a way that both suits and takes advantage of local conditions. We humans tend to be smart like that. 🙂

Images: Double decker by roman korzh via Flickr (CC BY-NC-ND 2.0). Second double decker by Ashwin Kumar via Flickr (CC BY-SA 2.0). Closeup of stone walkway by roman korzh via Flickr (CC BY-NC-ND 2.0).

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