MICHELE NORRIS, Host:

From NPR News, it's ALL THINGS CONSIDERED. I'm Michele Norris.

It's big, it's green, it's alive, and it's warming up our planet. But exterminating this threat is not an option. It's something billions of people depend on to survive.

For our series Climate Connections with National Geographic, NPR's Jon Hamilton traveled to Asia and filed this report.

(SOUNDBITE OF MUSIC)

JON HAMILTON: Okay. You've heard a lot about climate change. Glaciers are melting. Polar bears are drowning - all because cars and planes and power plants are spewing carbon dioxide into the atmosphere. But there's another important greenhouse gas, and it comes from rice fields like this lush green paddy in central Thailand. The crops here belong to a man named Pin(ph).

PIN: (Spoken in foreign language)

HAMILTON: Like a lot of farmers in Asia, Pin started working in the fields when he was 7 or 8. He used to pull weeds after school. Pin is 65 now and has spent his life learning how to coax the most rice possible from every square meter. He's deeply wrinkled from his years in the sun. At the moment, though, he isn't working. He's standing in the shade of a banana tree, watching a curious spectacle - a scientist is doing an experiment in his field.

The scientist is a graduate student named Tasny Jerapasuena(ph).

TASNY JERAPASUENA: I'm Miss Tasny...

HAMILTON: But everyone calls her Kim. She's balanced and steadily at the end of a wooden catwalk in the middle of the flooded rice paddy. Rice farmers flood their fields to discourage weeds and pests. Kim is putting together a tall wooden box, about the size of a barstool. She's already anchored the base of the box in the mud several feet under water.

JERAPASUENA: (Through translator) We put down the base on the - on top of the soil and leave it there so as not to disturb any gases. Then, we place the box on top of the base and then close the box with the cover.

HAMILTON: The top third of the box remains in the tranquil, sunny world above the waterline, surrounded by swaying rice stocks. But the bottom sits in the dark ooze of dead and rotting plant matter. It's a world with almost no oxygen - the perfect environment for tiny organisms that feed on dead plants. And as they feed, they produce a gas that bubbles up into the atmosphere or into the box that sits in Pin's rice field. The gas is methane.

Kim attaches a syringe to a valve on top of the box.

JERAPASUENA: (Through translator) Then, you draw 10 millimeter of gases in the chamber.

HAMILTON: Methane isn't as common or as well known as carbon dioxide, but it's more than 20 times as potent in its ability to warm the earth. Each rice field produces a relatively small amount of methane. But rice fields stretch across thousands of miles of Asia. Put together, they would occupy an area twice the size of Texas. And each year, the world's rice fields produce about 100 million tons of methane. Cutting that amount could have quite an impact on global warming, and that's what scientists are now trying to do.

The worldwide epicenter of rice science is here at the International Rice Research Institute in the Philippines. They keep seeds from every known variety of rice.

Reiner Wassmann is the climate scientist at the institute. He's the guru of rice field methane. And he's been working on the problem for decades.

(SOUNDBITE OF RICE MIXING)

REINER WASSMANN: (Climate Scientist, International Rice Research Institute) Well, I think there are strategies to reduce methane emission from rice.

HAMILTON: Such as draining the flooded rice fields periodically. That exposes the soil to oxygen, which kills many of the organisms that make methane.

But Wassmann says there's a catch - farmers use a lot of nitrogen fertilizer, so you have to drain the field at exactly the right time to avoid releasing that nitrogen into the air.

WASSMANN: It's not that easy because one has to be careful that one doesn't increase another greenhouse gas, which is called nitrogen oxide, at the same time.

HAMILTON: But he says the biggest obstacle is that rice farmers don't want to change the growing techniques they perfected over centuries.

WASSMANN: The question is, what are the incentives for farmers to do it? And here, I think, is we hear the problem. Why should farmers do that?

HAMILTON: Especially, because the changes often reduce their rice harvest. Wassmann knows about that firsthand. He works with King Monkut's University in Thailand, which is running the experiments in Pin's fields.

(SOUNDBITE OF FLOWING WATER)

HAMILTON: The researchers have tried draining his fields at different times. They have tried burning leftover rice crop to reduce the amount of decaying plant matter that accumulates under water. Pin isn't impressed. He's out of the shade now, inspecting his crops and complaining about the price of rice.

Have you ever heard of climate change?

PIN: (Foreign language spoken)

HAMILTON: Sure, he says. If the weather gets warmer, then there will be more pests.

Global warming is not good for the rice farming?

PIN: (Foreign language spoken)

HAMILTON: He says he's not sure about that. If there are more pests, he'll just use more pesticide. He's found a new brand that kills pretty much everything. Pin doesn't have much to say about methane. But he is happy to have the scientists around. He's hoping they'll stop measuring methane long enough to test the acidity of his soil. Now, that's something that could help him grow more rice.

Jon Hamilton, NPR News.

NORRIS: The world's rice fields don't just contribute to global warming. They are also threatened by the severe weather that climate change will bring. Jon Hamilton has that story tomorrow on MORNING EDITION.

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