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Wednesday, September 29, 2010

Living Bridges in India Have Grown for 500 Years (Pics)

by Brian Merchant, Brooklyn, New York 
Images via Atlas Obscura
Some of the smartest, most sustainable engineering feats were discovered hundreds of years ago, and many have gone unacknowledged. For evidence, take the bridge growers of northeastern India. Planning 10-15 years in advance, they build what may be the most sustainable foot bridges in the world -- by literally growing them out of living tree roots. These bridges are extremely sturdy, reach up to 100 feet long, and many are at least 500 years old.

Requiring the harvesting of only a few betel nut trees to create, each root bridge is sturdy, efficient, and, well, alive. A tribe in the hilly Khasi and Jaintia region of India -- one of the wettest places on Earth -- evidently came up with the concept some hundreds of years ago. Atlas Obscura explains:
The War-Khasis, a tribe in Meghalaya, long ago noticed this tree and saw in its powerful roots an opportunity to easily cross the area's many rivers. Now, whenever and wherever the need arises, they simply grow their bridges.
In order to make a rubber tree's roots grow in the right direction--say, over a river--the Khasis use betel nut trunks, sliced down the middle and hollowed out, to create root-guidance systems. The thin, tender roots of the rubber tree, prevented from fanning out by the betel nut trunks, grow straight out. When they reach the other side of the river, they're allowed to take root in the soil. Given enough time, a sturdy, living bridge is produced.
Sure, "enough time" isn't exactly expedient by today's standards -- each root bridge takes between 10-15 years to grow strong enough to be put into use. But strong they are -- evidently up to 50 people can cross the heftier bridges at once, and many bridges are over 100 feet long. And they only become stronger with time, as the roots continue to grow. Some of the bridges still in use in the region are estimated to be 500 years old.
An interesting side note nestled in this story is that the villagers who use them wanted at one point to tear them down to trade them for steel ones, for the sake of modernization -- but once a nearby resort owner stumbled upon them and recognized their potential value, the locals were easily persuaded from trading in (and untold materials and emissions were prevent from being wasted). The old bridges were still fully functional, after all -- in fact, the Khasis are still growing more bridges today. Chalk up another win for innovative sustainable design, however ancient it may be.



Anonymous October 4, 2010 at 11:50 AM  

Todo dinбmica y muy positiva! :)