The biology of bridge-building

When you think of bridges you don’t usually think of biotechnology or gardening. But that is exactly what the Khasis traditionally did. First you have a gorge to be bridged, then you find two rubber trees facing each other across the gorge. Next you coax the roots towards each other, perhaps along poles or planks. Then, when the roots meet each other, you begin pleating them together and, by a process called pleaching, encourage them to fuse. That’s how the bridge that you see in the featured photo was built.

Once the platform is ready, layers of mud are laid down over it to make a easily traversed road. I suppose the weight that the roots can carry is a concern. On the day that we were there a couple of people were standing at each end of the bridge to do some traffic control, mainly to make sure that the platform was not overloaded.

If the general shape of the bridge looks familiar, it is because it is structurally a cable-stayed bridge. The framework of joined roots forms a platform which could sway in a monsoon storm. As you can see in the photo above, branches are brought
down to stay the platform. As an engineering design, Mumbai’s sea link is no different from this. Interestingly, it seems that the whole community which uses the bridge is trained to carry out repairs on it, so that a villager passing by can braid the roots a little and put up a truss to guide a branch.

This particular living root bridge was close to Mawlynnong village. There are many of these bridges scattered across the Khasi and Jaintia hills. I guess it takes time for the tree to grow, but it can’t be many years. I’ve seen other Ficus trees grows roots which touch ground within months. So I guess it might take no more than a decade to make a bridge. Ficus elastica, the rubber plant, is said to live for about 200 years in the wild. So, during its lifetime the bridge would get stronger. If the community plans well, then they can even begin to replace an old tree before it dies. It is said that one of the root bridges near Sohra (Cherrapunji) has lasted 500 years. This could be hearsay, since the earliest documentation of these structures was published in 1844 in the Journal of the Asiatic Society of Bengal. However, it is not unthinkable that this could happen, given that the technology is widely shared between tribes.

The banks of the river here were not very high. In winter the water reduces to a trickle. So I climbed down to the river bed to take a look at the interesting flat stones along the bed. Much of the clan had already gathered here. The pools and stones were nice and cool after the climb down to the river from the road. I was impatient to get back up. People were selling cut pineapples dipped in red chili powder on the track, and I needed some of that.

Author: I. J. Khanewala

I travel on work. When that gets too tiring then I relax by travelling for holidays. The holidays are pretty hectic, so I need to unwind by getting back home. But that means work.

15 thoughts on “The biology of bridge-building”

  1. That’s brilliant. I don’t think we have any such bridges in Europe, though certain trees could be suitable. Willow is used in a similar way to fashion living shelters though.

    Like

  2. Happy to hear people manning the bridge so that it doesn’t get over crowded. Also, it looks less crowded than I had expected. Someone had told me it’s like a fish market now with the number of people all over. My nephew had gone to Mawlynlong recently for a project and the pictures he sent was upsetting as there were so many constructions in and around. He aptly named the picture series as ‘A Village No More’. I had visited just in 2016 and it was really beautiful then. Did you go there before? If yes, did you notice such not-so-good changes?
    Lastly, I love those pineapples sprinkled with chillie powder and salt!

    Like

  3. Thanks for the link in your comment on my treehouse-post. I had already read this in February, as well seen a film about it. But seeing this live must be definitely more impressive. Thanks for sharing!

    Like

Leave a Reply to Gavin (Firehorse) Cancel reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.