Monday, June 11, 2007

Root Bridge

Recd from Supratik, IITB

I was recently in a tribal area of Meghalaya, and was completely stunned by the ingenuity of the indigenous people who have "trained" living roots of a species of rubber tree (Ficus elastica, we were told) to form bridges, complete with railings, over small, but fast flowing, mountain streams. In brief, this species of rubber tree has lateral roots that emerge from the trunk (above the ground) and can grow laterally for some distance before hitting the ground. Khasi tibals have been using hollowed out betel nut trunks/branches as guiding channels in which young live roots of the rubber tree (still attached to the trunk) are allowed to grow for years. The channels are used to direct the roots in specific directions across the mountain streams, and also to form railing-like support structures to help a person hold on to when walking on the roots.

Once a few roots have been successfully channelized to grow in the desired direction, it is easy to have other roots grow in the same direction by using the earlier roots as support structures and guides. The process apparently takes 25 to 30 years for a set of roots to cross the river and hit the ground on the other bank, and become strong enough to take the load of a few human beings. So this is indeed testimony to the patience and conviction of the Khasi tribal people -- waiting for 25 to 30 years to build a masterpiece of bio-engineering. Once the bridge is formed, it only grows in strength over years, as the roots thicken and further fresh roots join the bridge.

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