Flower Power: Rising Carbon Dioxide Is Great for Plants

By Wittwer, Sylvan H. | Policy Review, Fall 1992 | Go to article overview
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Flower Power: Rising Carbon Dioxide Is Great for Plants


Wittwer, Sylvan H., Policy Review


One of the best-kept secrets in the global warming debate is that the plant life of Planet Earth would benefit greatly from a higher level of carbon dioxide (CO2) in the atmosphere.

You read that correctly. Flowers, trees, and food crops love carbon dioxide, and the more they get of it, the more they love it. Carbon dioxide is the basic raw material that plants use in photosynthesis to convert solar energy into food, fiber, and other forms of biomass. Voluminous scientific evidence shows that if CO2 were to rise above its current ambient level of 360 parts per million, most plants would grow faster and larger because of more efficient photosynthesis and a reduction in water loss. There would also be many other benefits for plants, among them greater resistance to temperature extremes and other forms of stress, better growth at low light intensities, improved root/top ratios, less injury from air pollutants, and more nutrients in the soil as a result of more extensive nitrogen fixation.

This good news about carbon dioxide has been all but ignored in alarmist discussions about possible global climate changes. CO2- related benefits were barely mentioned at the Earth Summit in Rio de Janeiro in June, where the rising level of carbon dioxide and other "greenhouse gases" was decried as the world's greatest environmental threat. The Rio Summit ended with the United States and over 150 other nations signing a Framework Convention on Climate Change, committing themselves to stabilizing emissions of CO2 and other greenhouse gases at 1990 levels.

Indeed, the conventional wisdom in public policy circles is that carbon dioxide is a terrible pollutant that threatens the fate of the earth. Senator Albert Gore, the Democratic vice-presidential candidate, calls for stiff "carbon taxes" on the burning of fossil fuels, and has written in his book Earth in the Balance that the process of "filling the atmosphere with carbon dioxide and other pollutants...is a willful expansion of our dysfunctional civilization into vulnerable parts of the natural world."

On the Republican side, William K. Reilly, President Bush's administrator of the Environmental Protection Agency, defends the $20 billion in costs that the Clean Air Act of 1990 has imposed on the U.S. economy, in part on the grounds that it "will eliminate 56 billion pounds of pollutants annually, many of them greenhouse gases."

And yet, for over 100 years, nurserymen have been adding carbon dioxide to their greenhouses to raise the yields of vegetables, flowers, and ornamental plants. And for decades, it has been well known among botanists, biochemists, agriculturalists, and foresters that a shortage of carbon dioxide is the most common limiting factor preventing photosynthesis from proceeding more efficiently.

The Global Warming Debate

There is no question that the carbon dioxide level in the atmosphere has been rising, and that this rise is due primarily to the burning of fossil fuels and to deforestation. Measured in terms of volume, there were about 280 parts of CO2 in every million parts of air at the beginning of the Industrial Revolution, and there are 360 parts per million (ppm) today, a 30 percent rise. The annual increase is 2 ppm, and rising. If present trends continue, the concentration of CO2 in the atmosphere will double to about 700 ppm in the latter half of the 21st century. This increase would not be a direct threat to human life; the threshold in mine-safety regulations is 5,000 ppm of carbon dioxide. But a man-made change of this magnitude in the atmosphere requires careful efforts to understand its consequences.

A number of climatologists have used computer models to predict a rise in global temperatures of 2 to 9 degrees Fahrenheit over the next century as a result of this projected rise in CO2 and other greenhouse gases, such as methane. The global warming hypothesis is disputed by many climate scientists.

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