Using the Right Tools


Richey already had a lot of the river water samples he needed. Between 1982 and 1992, he and his colleagues had periodically gone out on six-week river cruises on a 60-foot, double-decker research boat. In describing those thousand-kilometer expeditions, Richey says, “The Amazon is almost beyond anything you can imagine. There’s this vast life and energy surrounding you. The sky is moving. The river is swirling and churning. There are birds everywhere. Then you get off the big boat and into outboards to go into the narrower floodplains, and you are overwhelmed by the smell of all the vegetation. And all day, there’s the pressure of the sun.”

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Photograph of Scientists Sampling Water


In addition to the standard, canned, camp fare you’d expect on a month-long research venture into the depths of the Amazon, Richey says the crew ate delicious local food, especially the fish they bought from local fisherman. The trips were not always idyllic, however. The researchers had one of their scarier moments after being confronted by a local tribe who mistakenly thought the researchers had arrived to take them away and claim a bounty on the tribe offered by drug traffickers. Richey and his colleagues beat a hasty retreat, more than willing to sacrifice a few data points to preserve the peace.

Richey and his colleagues collected more than 1800 river water and air samples within the central Amazon River Basin. In some cases, they used huge winches to haul up samples from deep in the river. In other cases, they captured gas emissions from the water surface using what Richey called “floating dishpans,” and described as inverted bowls placed over the water.

The second piece of information Richey needed was a good estimate of just how big an area was covered by water during the year. The Amazon may be perpetually wet, but it is wetter at some times than others. From December to May each year, torrential rains and snow melt from the Andes increase the main river channel’s depth 30 to 45 feet, and water backs up in tributaries and inundates forest miles from the main channel. The river and the flooded forests, called várzea in Portuguese, become a giant, slow-moving swamp. Richey needed to know how big.

  Richey’s team measured the carbon dioxide dissolved in the Amazon Basin’s rivers by sampling the water directly. A decade of river cruises gave the researchers extensive knowledge of the region. (Photograph courtesy Jefferey Richey, University of Washington)

Photographs of Vereza in the Dry and Wet Seasons


Given the immense area under study, an afternoon trek through the jungle with a camera in hand was out of the question. Satellite mapping was the only real possibility; satellites such as NASA’s Landsat series had been mapping the Amazon basin for years in true- and false-color imagery. Optical sensors like those on Landsat, which work like digital cameras, have a serious limitation, however. If there is one thing that you can count on in the Amazon during the wet season, it’s rain. At precisely the time of year when Richey needed imagery to reveal the extent of the flooding, the rain clouds hid the forests from a satellite’s view. To map the flooded Amazon forests, Richey needed a remote-sensing device that could see through clouds. He turned to radar.

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The area covered by water in the Amazon isn’t constant; it varies wildly with the change of seasons. The várzea—flooded forest—is inundated every May by rain and Andean snowmelt. (Photographs courtesy Max-Planck-Institute for Limnology)