Human Planet tonight. On rivers.
This video's not from it, but it depicts something quite amazing that I first heard of on the show. In the Indian state of Meghalaya, one of the wettest places on land, in order to cross the raging torrents that the rivers become every rainy season the people use living bridges constructed over decades from the peculiar secondary roots that grow from the trunks of the Indian rubber tree (
Ficus elastica) and maintained for centuries. They still build/grow/cultivate them today, as connecting the roots and passages in the forests is still on going after hundreds of years.
They encourage the roots to grow long through tubs of bark, until they are long enough to reach across the water. Once the end has settled on the other side, the connection is secure and they can begin to grow it into a bridge, weaving the base and the sides, waiting for them to grow hard and strong, and even paving them. The very bridge is living, so it won't require repair or replacing from age and wear. I was enthralled.
Here are some finished bridges.