I expect most of us have at some point crossed a river or a ditch using a tree – either a fallen one, or a tree in just the right place. But at the Our Time on Earth exhibition last week at the Barbican, I was rather impressed with an exhibit that learns from the indigenous architecture of the Khasi tribe in Meghalaya, north-east India.
I say architecture, though this stretches the usual definitions considerably. This is architecture without architects, and also without buildings. What the Khasi do is create living bridges out of the intertwined roots of local fig trees. They are unique, beautiful, and they have a whole series of advantages.
Take, for a start, that is the only form of infrastructure that gets stronger over time. As the trees grow and the roots thicken, the bridge becomes stronger and self-sustaining. Some of the bridges in daily use today are centuries old, and these bridges are sturdier than the new ones.
Because they are alive, root bridges are always a work in progress. They are long-term projects, and inherently social: the person that first starts the bridge may not live to see it fully functional, and future generations will keep tweaking them for as long as they remain in use.
They begin with manipulating and overlapping supple young aerial roots. Sometimes roots are encouraged in the right direction with bamboo scaffolding, sometimes not. As the bridge takes shape, new roots can be wound in to support it, or to create handrails and barriers. There are multiple techniques, often highly localised, and generally using free materials available from the forest. That’s an unusual feature of living bridges too. Very little infrastructure comes free from the landscape.
Despite their organic nature, the bridges that the Khasi make are superior to many of the alternatives. Concrete and steel would be expensive, and impractical in remote areas without roads. Traditionally constructed wooden bridges would rot or get washed away in monsoon floods. A living bridge is better, and is in no way an inferior or primitive technology.
As the exhibition pointed out, there is no reason why other parts of the world could not learn from the living architecture of the Khasi. They imagine a city using living pedestrian bridges, giving citizens an elevated walkway, and creating shade beneath.
Whether anyone will build such a thing remains to be seen, but I was fascinated by living bridges. If you’re anything like me, you can thank me later for pointing you towards The Living Root Bridge Project, which has lots of photos and details.