Soils and atmosphere intricately linked

June 18, 2004 - Scientists tell us that of all the issues facing humanity this century, the biggest challenge may be climate change. Over the next few decades, a warming planet could begin to have profound implications for our economy and our way of life. Yet this important issue is virtually nowhere to be found in Canada's election debates.

To understand the urgency of the climate situation, open up the latest edition of the prestigious journal Science. Here's a special issue devoted to soil. Yet what is the issue brought up again and again? Global warming.

Here's why: Just as our body is a composite of many different organs, the biosphere is one big, interconnected system of many component parts. Air, water, soil and all living things are parts of it. Major changes to one of these components can have a ripple, or feedback, effect through all of them in the same way that a stroke or heart attack reverberates through the rest of the body. And that's what's happening with global warming. By adding heat-trapping gases like methane and carbon dioxide to the atmosphere, we are heating up the planet and causing changes throughout the system.

So what does this have to do with soil? Plenty, as it turns out. Soil holds carbon that may otherwise be released into the atmosphere and contribute to global warming. Permafrost - soil that normally stays frozen year round - is especially effective at holding carbon because the cold prohibits the breakdown of organic matter. It's estimated that a quarter to a third of all soil carbon is locked in permafrost.

But as humans have heated up the planet, permafrost has started to melt. In Northern Manitoba, the rate of thaw has tripled over the past four decades, and according to an article in Science, permafrost is receding northwards by 31 centimeters a year. What melting permafrost will mean for climate change is a big unknown. It's possible that new plant growth could eventually absorb some of the carbon released as the soils melt. But that could take decades. In the meantime, wet decomposing organic matter in the soils could release huge amounts of methane, an extremely powerful greenhouse gas, which could make global warming much worse.

As global warming intensifies, other soil-related problems also come into play. More extreme weather will mean more soil erosion, which could reduce crop yields and expand deserts. Warming soils will also speed up the decomposition of organic matter, which could reduce soil fertility as well as release more carbon into the atmosphere.

However, soils don't necessarily have to be a source of carbon. By working to restore degraded soils and improve agricultural practices, soils could absorb more carbon than they release, helping to slow global warming. In fact, some experts say that using a variety of strategies, from no-till farming, to more efficient irrigation and growing mixed crops, soils could absorb five to 15 per cent of total carbon emissions. In addition, such practices would improve soil fertility and crop yields, helping to reduce hunger.

So, here we have a problem that is human made. There is strong scientific consensus that it is a big, big problem. Canada, by ratifying the Kyoto Protocol, has promised the world that we will take some responsibility and start working on it. Yet in this election it is virtually nowhere to be found.

We've faced other big environmental problems before, from lead in gasoline and ozone-depleting substances, to persistent pollutants that build up in the food chain. Each time, the international community has worked together to solve them - and we did. Lead has been virtually eliminated, the ozone layer is beginning to heal and persistent pollutants will now be phased out.

We can do the same thing with global warming - if we demand action from our leaders. It's not too late to find out where your candidates stand on this issue and ask them to make it a priority.

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