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CO2 is Good for Plants: Another Red Herring in the Climate Change Debate

Posted on 1 July 2010 by Mariana Ashley

Guest post by Mariana Ashley

CO2 feeds plants. And so, too, does ignorance and a little bit of politicking feed inane misconceptions. Rep. John Shimkus of Illinois made famous the CO2 as plant food argument during a U.S. House Subcommittee on Energy and Environment hearing in 2009. The basic plant food argument is that since plants need CO2 to grow, more CO2 means, by proxy, more sustained and robust plant growth globally.

A quick look at the science behind this argument demonstrates its inherent weaknesses. In closed, controlled environments, like greenhouses and plant nurseries, an increase in CO2 does indeed spur plant growth. However, the globe is not a controlled environment, and it’s incredible sensitivity to a variety of factors is something that is often taken for granted when such narrow arguments are proffered. A rise in CO2 levels is not the only consequence of climate change, and it is these other effects that have had and will have more abiding adverse effects on plant growth around the world.

While CO2 is an important element that stimulates plant growth, the planet's flora requires a cocktail of elements to maintain its health. Arguably the most important of these elements is water. With the global increase in temperature caused by the various factors affecting our climate's balance, increased evaporation means decreased soil moisture. Another effect of global climate change is erratic precipitation patterns. This causes extreme weather in certain geographic locations only sporadically, with overall, balanced rainfall drastically reduced.

Suppose, however, that CO2 does prime plant growth in the world at large. To what extent will this happen? For one, the increased density of forest vegetation could increase the risk of wildfires, which have reared their ugly heads in California all too often in the past few years, wreaking devastating damage. Presumably the CO2 as plant food enthusiasts offer their argument in an effort to demonstrate the resulting agricultural advantages. But even if "CO2 fertilization" occurs, weeds proliferate in tandem with crops, which would only increase the global cost of agriculture.

We could discuss the scientific finer points of global climate change and the unlimited effects it could have on global plant growth all day. A Climate Denial Crock of the Week video does just that in debunking the CO2 plant food argument. However, at its most basic level, the CO2 plant food argument rests on a simple logical fallacy--the fallacy of exclusion, which focuses on one cause-and-effect (in this case, more CO2 means more plants) to the exclusion of all other cause-and-effect chains.

When CO2 is framed as an element good for plants in order to dismiss the other existing pieces of evidences that suggest the dangers of global climate change, we are left with an idea that only distracts us from the more pressing issues of our planet's increased loss of balance.

This guest post is contributed by Mariana Ashley, who writes on the topics of online colleges. She welcomes your comments at her email:

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Comments 101 to 104 out of 104:

  1. johnd, the paper focus on the response to elevated CO2 concentration (720 ppm) in a controlled experiment. I don't think it can be extrapolated backward and in a generic environment.
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  2. Riccardo at 09:17 AM, I wasn't meaning extrapolating backwards, but to what has shown up in actual observations within the natural environment. The study of plant growth is not a new science. CO2 began it's upward trend over 100 years ago and has accelerated in recent decades. If any short term effects from increased CO2 fertilisation disappear after a few years, then such effects should have been readily observable long ago in any studies of plant growth, as well as in the horticultural industry where it has been practiced for decades. It would also mean that current experiments should see an immediate decreased response to growth, but even in the experiment cited, that apparently was not the case.
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  3. johnd, real life is different from a controlled experiment. It's already difficult enough to assess the effect in controlled experiment at CO2 concentration more than double current value to think that it should have already be noticed in managed (hyper-fertilized) farms.
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  4. I have always likened that "CO2 is good for plants" notion to the idea that extra calories are good in the human diet. How about those diabetes and heart attack epidemics? It might be good in the short term to pack on extra weight, but in the long run, it's deadly.
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