Deforestation, logging threaten the battle

April 28, 2007
Cameron Smith

In a sense, we've been living on borrowed time and it will run out if we don't learn to work with the land instead of against it.
Trees and other land plants have been moderating the march of global warming by increasing the amount of carbon dioxide CO2 they remove from the air. However, there's a limit to what they can do.
By the end of the 1990s, land plants were capturing seven times as much CO2 as they had been in the 1980s an estimated 1.4 billion tonnes compared to 200 million tonnes. In doing so, they countered skyrocketing emissions resulting from tropical deforestation.
Warmer temperatures, longer growing seasons and earlier springs made the increased capture of CO2 possible, along with better land management outside the tropics. However, the recent report from the Intergovernmental Panel on Climate Change warned that if the world stays on its current path, in less than 40 years land plants will lose their battle to hold the line.
The result will be an increase in the rate of global warming. This is uncomfortable news because it brings up the troubling issue of feedbacks when higher temperatures set off an ever-quickening spiral of global warming, as will happen, for instance, if large tracts of permafrost melt and release methane, a greenhouse gas 21 times more potent than CO2.
This is already happening on a small scale, but the warning is ominous: If the methane genie gets out of the bottle, we can forget about a habitable world.
Recently, a team of researchers, led by scientists at the University of Alaska Fairbanks, were surprised to find methane being released five times faster than expected at "thaw lakes" created by melting permafrost in Siberia. The research is reported in Nature, Sept. 7, 2006, pages 71-75.
Even in the dead of winter, methane escaped because water under the ice insulated the melting permafrost. When a hole was cut in the ice, escaping methane could be ignited and flared.
Estimates of the amount of methane in the world's permafrost vary widely, from an amount that would equal half the CO2 already in the atmosphere, to an amount 20 per cent greater. If only 1 per cent of the larger estimate were released each year, it would equal the total annual rate of emissions from deforestation and burning fossil fuels.
So, will it be possible to slap at least a partial lid on permafrost feedback? A group of British and U.S. researchers say yes. Their report is published in Nature, April 12, 2007, pages 727-728.
They point out that deforestation has had devastating results. "Over the past 200 years, it is thought to have been responsible for 30 per cent of the (human-made) increase in atmospheric CO2 concentrations."
Curtailing deforestation, together with adopting sensitive land-use practices such as no-till agriculture, more efficient fertilizer use, and planting vegetation with higher abilities to sequester CO2, will preserve the ability of plants to limit global warming, they say.
To give an idea of how much help we could expect from plants if we gave them this chance, the authors point out that "throughout history, soils are thought to have lost between 40 billion and 90 billion tonnes of carbon globally." This loss could be reversed if their recommendations were adopted, they say, and "a cumulative increase in terrestrial carbon of up to 100 billion tonnes is possible by 2050."
Creating an additional 100 billion tonnes of terrestrial carbon would be equivalent to eliminating all emissions from deforestation and burning of fossil fuels for 11 years.
Now, to pose a question that takes us down from the global general to the Ontario particular: What is Ontario planning to do about preserving its northern boreal forest as a prime agent in restraining global warming?
The answer, so far, is nothing. Premier Dalton McGuinty has not yet fulfilled his election promise of holding back mining and logging expansion into the northern boreal forest until broad-scale land-use planning is completed.
In light of what scientists are telling us, all that can be said of this unkept promise is: "For shame, Mr. McGuinty."