Wacky WorldIndia
Khasi and Jaintia communities guide rubber-tree roots across streams; some bridges are centuries old.
Why it happens
In the Khasi and Jaintia Hills, rivers swell violently in the monsoon and wooden bridges rot quickly in the wet. The Indian rubber tree (Ficus elastica) grows aerial roots that can be guided. Villagers lay hollowed betel-nut trunks or bamboo across a stream and thread the young roots through them. Over 15 to 30 years the roots reach the far bank, take hold in the soil and thicken into a bridge that grows stronger with age instead of weaker.
How we know
Researchers from the Technical University of Munich surveyed 74 of these bridges for a 2019 study and found they are maintained continuously by village communities, sometimes for generations. The best-known is the double-decker bridge at Nongriat, which has two root spans one above the other.
Did you know?
A healthy root bridge can carry dozens of people at once and is expected to last for centuries. Architects now study them as a model for “living architecture” in cities.
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