Introduction to the Greening Theory

The amount of carbon dioxide in the air is increasing. This means that the food available to the earth's plants is increasing. What happens when food increases? It usually means that things grow more and that more things grow. With animals it is typical for populations to increase when food increases. Plants can also adapt to improved conditions by growing larger, faster and more robustly.

The hypothesis that the number and/or size of plants has increased and will continue to increase because of the increase in CO2 is called the Greening Theory. Detailed information about the Greening Theory can be found at the Idso Center for the Study of Carbon Dioxide and Global Change. Sherwood Idso was one of the early proponents of the Greening Theory and the center is run by his sons Keith and Craig, who have carried on his work. Likewise, the Greening Earth Society has several videos and numerous other resources on the Greening Theory.

Much of the research on CO2 increase and plant growth is done under the rubric of "sequestration" of carbon. Those who view the CO2 increase as a threat due to climate change see sequestration as a possible way to mitigate this threat by taking CO2 out of the air. Sequestration assumes the truth of the Greening theory.

One needs to keep in mind that as CO2 is only one molecule out of 3000 or so, it is very hard work for plants to get those CO2 molecules. Yet 93% of all (dry) plant matter is derived from CO2. The CO2 level has increased by about 30% in the last 150 years, most of that increase coming in the last 50 years, when population growth has been greatest. Increasing the concentration by 30% is a very big deal from an engineering point of view. It means plants only have to find one molecule out of 3000 in the air instead of one out of 4000. The response need not, probably should not, be linear. So the plausible range of effects is probably between 10% and 50%. We call this the greening effect.

The biggest confusion is that people talk of CO2 as fertilizer. Fertilizer is to plants what vitamins are to people. CO2 is not fertilizer, it is food, the principle food of plants. Each plant's body, and therefore all bodies of living things, are built primarily from CO2. Most people do not understand this. It is one thing to say that CO2 is essential for life, which every biology book does. It is quite another to actually get people to understand that when they eat a steak they are eating processed CO2. That when they watch the leaves come out, they are watching CO2 being processed. That when they watch their child grow, they are watching processed CO2 being further processed. Plus that CO2 is a rare gas, therefore not to be blithely curtailed.

That CO2 is the basic food of all living things is important because the basic hypothesis underlying the Greening Theory is therefore that food is the principle limiting factor in plant growth and population. This is the prima facie assumption of ecology. Food is the usual limiting factor for any population, not predation, disease, vitamin deficiencies, etc. The latter are special cases.

The Greening Theory says that increasing CO2 should increase plant growth. So does a huge body of experimental evidence -- thousands of experiments. So does observation, ranging from commercial greenhouses using CO2, to the recent global carbon sink findings.

More information about the carbon dioxide increase can be found at the Carbon Dioxide Information Analysis Center (CDIAC) of the Oak Ridge National Laboratory.

More information about greening effect research can be found at these sites, with many links to others:
1. The National Agricultural Library of the U.S. Department of Agriculture.
2. FACE - Free Air Carbon Dioxide Enrichment web site.
3. Updated Bibliography on CO2 Effects on Vegetation at ORNL.
4. GCTE Home Page.
5. MEDLINE Journals With Links to Publisher Web Sites.
6. NCAR/CGD Home Page.
7. C4: The Center for Clouds, Chemistry, and Climate.
8. U.S. National Climatic Data Center (NCDC).
9. AMS Journals Online.
10. Global Warming International Center.

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