The Molecule That Made Us

(plane engine revving) -

Narrator

Scientists have developed a unique technology to follow the droughts, and to measure the amount of water held in the vegetation below. We have the (mumbles) clouds up. -

Narrator

They call him Greg Asner, the drought chaser. -

Greg

We have found ourselves, chasing these drought events. And when I say chasing, it's somebody calling me up and saying, "Greg we have this drought, could you come and help us to make that assessment?" And it used to be that we'd get that call once a year, and now I'm getting that call, I'm not kidding, at least once a month, if not once a week. (plane engine revving) -

Narrator

Greg's technology can see and measure water in ways impossible with the naked eye. As he flies over, LIDAR scanners use a laser to create a high resolution 3D map of the forest below. At the same time, Greg's cameras record a spectral image, which means they can see the chemical makeup of each tree, including the movement of water in the canopies. In 2010, the drought chasers were called in to analyze a drought in the Amazon. -

Greg

We had this mega drought show up, across a lot of the Amazon basin, especially in Brazil. The imaging systems onboard our plane were lighting up, literally the big screens were showing, enormous amounts of loss. And we saw this everywhere all over the western Amazon. We saw mortality that easily was over 50% of the tree canopy. And the reason this is alarming is that at any given moment in time, you would expect to see about one to 2% of the canopy in the state of dying just naturally. When you see 50%, 50 times the rate, you don't have words for it. -

Narrator

Scientists like Greg Asner believe, if just 25% of the Amazon is lost. It will reach a tipping point that could fatally damage the rivers that fly above the forest. People like Antonio Nobre think we're already there. And in 2015 there were worrying signs. He might be right. 2000 miles away and Brazil's biggest city, Sao Paulo, a flying river had stopped its flow and the people running out of water. (crowd rioting) Antonio Nobre lives there. The drought struck us, you know, head on and, and I started getting really concerned. The army started preparing for riots, because imagine 22 million people, in the largest Brazilian metropolis running out of water. And people got so was, like, what are we going to do? We don't have water not even for drinking. The only explanation is that we are damaging dams. You damage the forests, you damage the flying rivers, therefore, you damage the water cycle the pulses stop, it's like a heartbeat that all of a sudden stops. -

Narrator

While we were filming here, we found one of the most unexpected effects of the Amazon drought on the Rio Tiete. Normally there's enough water to flush pollutants from Sao Paulo up to the sea. But in the drought, the pollution intensifies, phosphates and industrial chemicals combine to create this toxic foam. To kayak here, you have to wear a biohazard suit. It is the saddest image of a river I have ever seen. Multiple organ failure, you have that term in intensive care units. Multiple organ failure, it's going on right now on the planet.