Soil & Global Warming

Soil & Global Warming Photo Credit: Clipart.com.

One of the biggest environmental worries is global warming, which is caused by greenhouse gases like carbon dioxide. In this Science Update, you'll hear how dirt might help fight it.


Putting greenhouse gases in the ground. I'm Bob Hirshon and this is Science Update.

The burning of fossil fuels releases carbon dioxide into the atmosphere, the chef cause of the greenhouse effect. But for centuries, agriculture was the culprit. That's because tilling and plowing expose more soil to the air, causing the carbon there to react and escape as carbon dioxide gas.

Modern farming techniques slowly began to reverse this process. But senior scientist Jim Amonette of the Pacific Northwest National Laboratory wants to speed it up—to help fight global warming.


What we were trying to do is just figure out what the slight small thing a farmer or agricultural manager could do to increase the amount of carbon retained by their soil.

His team found that making the soil less acidic, changing irrigation patterns, and promoting the formation of certain minerals can make a big difference. Amonette says that some soils could potentially double their carbon content to as much as five percent by weight.


So that means that an acre of soil six inches deep could contain 100,00 pounds of carbon. So a lot of carbon could be stored in an acre of topsoil.

It's hoped that these techniques could help put greenhouse gases safely under our feet. I'm Bob Hirshon for AAAS, the Science Society.

Making Sense of the Research

You've probably heard of the greenhouse effect, which is the trapping of heat by certain gases in the earth's atmosphere. And you've probably heard about these gases coming from cars, factories, and other man-made machines. But farming?

As Amonette says, until recently, that's where most of the human-made greenhouse effect came from. Remember that when industrial farming really took off, about two centuries ago, the earth's soil contained about as much carbon as it could possibly hold. Now that much of that carbon has been released, there's plenty of room to soak it back up.

Unfortunately, cars, factories, and other human technologies are now pumping greenhouse gases into the atmosphere much faster than farming ever did. That's why Amonette and his colleagues are trying to help the soil soak up more carbon faster. In other words, they're using soil as a sink for carbon, to balance out the carbon from sources like cars and factories.

Amonette's goal was to speed up the activity of tyrosinase, an enzyme found in soils that's critical to carbon absorption. He says treating fields with commercially produced tyrosinase would be expensive and impractical. So instead, he tinkered with natural variations in soil care to see which conditions made tyrosinase work most efficiently.

The experiment involved trapping soil in 72 separate tubes. Each tube contained a soil sample that was exposed to slightly different conditions. Amonette found that soil acidity, the use of common additives, and irrigation patterns all could influence the efficiency of the soil's carbon uptake. And these are changes that farmers could make fairly easily at low cost.

Next, he plans to test his theories in the field, by treating large patches of soil in different ways. If his predictions from the lab hold up, they'll be able to make recommendations to farmers.

Now try and answer these questions:

  1. How can soils help remove carbon from the atmosphere?
  2. If humans had never invented farming, but still created the same level of air pollution we have today, would the soil be more, less, or equally able to remove carbon from the atmosphere? Explain.
  3. What is tyrosinase? What role does it play in this research?
  4. If these findings hold up, what do you think it would take to convince farmers to change their soil management practices?

For Educators

The National Oceanic and Atmospheric Administration's Global Warming FAQs is a good starting point for global warming research.

Fossil Fuel CO2 Emissions, from the Carbon Dioxide Information Analysis Center, provides information about the world's fossil fuel and CO2 emissions.

The Greenhouse Effect, from the EPA's Global Warming Kids Site, features information about the greenhouse effect.

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