In Meghalaya, India, locals have to deal with heavy rainfall and frequent flash floods along the many streams that supply water to the area. And yet this forbidding environment has given rise to an architectural practice that sounds like something out of environmental science fiction: for at least a thousand years, the people of this area have been building bridges using the root systems of rubber trees.
The process usually takes at least two decades, and requires careful planning that is reminiscent of how bonsai trees are created by slowly pulling branches in the desired directions. People guide the thick roots of the rubber trees in the direction they want using hollowed-out branches from betel nut trees. Over many years, the roots eventually find their way across the stream, and implant themselves in the mud of the opposite bank.
This system is an environmentally sustainable form of geoengineering. The roots stabilize the banks of the rivers, as well as providing an easy way for many people to cross to the other side. Some of the tree bridges are centuries old, and can carry up to 50 people at a time.
As cities and towns in other parts of the world look for sustainable materials to build their own infrastructure, these tree root bridges could provide a model. Imagine living in a city whose buildings and roads are made with living trees and other plants. Sounds like something out of a China Miéville novel.