Too much of a good thing

(May 12, 2011) An Edmonton Journal article takes issue with the views of Lawrence Solomon — and most scientists — on carbon dioxide.

Re: “Are high CO2 levels once again saving the Amazon forest?” blog excerpt by Lawrence Solomon, Opinion, May 9.

Lawrence Solomon’s blog excerpt is one that can mislead many readers.

The belief that high CO2 results in increased growth rates in plants is an oversimplification, especially since it is based on mostly greenhouse experiments, rather than much more complex outdoor settings.

A specific plant’s response to excess CO2 is sensitive to many factors, including age, genetic variations, functional types, time of year, atmospheric composition, competing plants, disease and pest opportunities, moisture content, nutrient availability, temperature and sunlight availability. The truth is that the negatives of drought and heat stress may cancel out any benefits of increased CO2. Excess CO2 can also have detrimental effects on plant health and nutritional content.

Furthermore, Solomon fails to point out the elevated CO2 did not help prevent the massive Amazon Basin droughts in 2005 and 2010. All the CO2 in the world is not going to help if there is not enough water for the plants to grow.

The Amazon was transformed from a CO2 sink to a source of CO2 during the 2005 and 2010 droughts -a positive feedback, with more warming, leading to more droughts, which leads to more CO2 being released. In fact, 57 per cent of Amazonia had low rainfall in 2010 as compared with 37 per cent in 2005.

Elevated CO2 is a case of too much of a good thing for plants. The resulting higher temperatures and droughts of increasing severity threaten not only the Amazon, but also other parts of the world, and hence the health of our entire planet.

Victor Dorian, Edmonton, May 12, 2011

To read Lawrence Solomon’s original blog, click here

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