Evidence of Positive Effects of Increased CO2 on Earth’s Plant Growth

27 05 2008

An accurate understanding of the natural processes associated with the fertilization of plants by carbon dioxide are critical in forming one’s opinion about the “man-made global warming” hypothesis. Do increasing levels of atmospheric CO2 ultimately have a positive or negative impact on plant growth? As is true in point after point in this debate about global warming and climate change, there is one school of thought that predicts increasing CO2 concentrations as damaging to plant growth, and another sees it as a positive. What you will read below is evidence for the “positive CO2 impact” point of view.

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This is the third post in a series presenting information from an academic paper by Arthur Robinson, et.al. from the Oregon Institute of Science and Medicine (http://www.oism.org/). In this paper Robinson and his co-authors address the “Environmental Effects of Increased Atmospheric Carbon Dioxide ” (click here for a downloadable copy). The Journal of American Physicians and Surgeons (2007) published this article (see the following reference)…..


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Environmental Effects of Increased Atmospheric Carbon Dioxide

Oregon Institute of Science and Medicine, 2251 Dick George Road, Cave Junction, Oregon 97523 [artr@oism.org]. Published in the Journal of American Physicians and Surgeons (2007) 12, 79-90.


Following are some direct quotations from the paper by Robinson, et.al.. Please go to the original paper for supporting figures and references, all of which have not be included in post. Any highlighting, underlined or bold text, or other attempts to emphasize particular parts of the text are of my doing (and not of the original authors).


FERTILIZATION OF PLANTS BY CO2: pp. 8-9 of original article

How high will the CO2 concentration of the atmosphere ultimately rise if mankind continues to increase the use of coal, oil, and natural gas? At ultimate equilibrium with the ocean and other reservoirs there will probably be very little increase. The current rise is a non-equilibrium result of the rate of approach to equilibrium.

http://www.geocities.com/dieret/re/Biomass/biomasscyc.jpg” cannot be displayed, because it contains errors. A simplified diagram of the carbon cycle

One reservoir that would moderate the increase is especially important. Plant life provides a large sink for CO2. Using current knowledge about the increased growth rates of plants and assuming increased CO2 release as compared to current emissions, it has been estimated that atmospheric CO2 levels may rise to about 600 ppm before leveling off. At that level, CO2 absorption by increased Earth biomass is able to absorb about 10 Gt C per year. At present, this absorption is estimated to be about 3 Gt C per year.

About 30% of this projected rise from 295 to 600 ppm has already taken place, without causing unfavorable climate changes. Moreover, the radiative effects of CO2 are logarithmic, so more than 40% of any climatic influences have already occurred.

As atmospheric CO2 increases, plant growth rates increase. Also, leaves transpire less and lose less water as CO2 increases, so that plants are able to grow under drier conditions. Animal life, which depends upon plant life for food, increases proportionally.

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(Following are examples from a large body of scientific studies showing increased plant growth in the last half century) …… (L)ong-lived 1,000- to 2,000-year-old pine trees have shown a sharp increase in growth during the past half-century. Figure 22 (in the paper) shows the 40% increase in the forests of the United States that has taken place since 1950. Much of this increase is due to the increase in atmospheric CO2 that has already occurred. In addition, it has been reported that Amazonian rain forests are increasing their vegetation by about 900 pounds of carbon per acre per year, or approximately 2 tons of biomass per acre per year. Trees respond to CO2 fertilization more strongly than do most other plants, but all plants respond to some extent.


Wheat growth is accelerated by increased atmospheric CO2, especially under dry conditions. Figure 24 (in the paper) shows the response of wheat grown under wet conditions versus that of wheat stressed by lack of water. The underlying data is from open-field experiments. Wheat was grown in the usual way, but the atmospheric CO2 concentrations of circular sections of the fields were increased by arrays of computer-controlled equipment that released CO2 into the air to hold the levels as specified.

http://www.debruce.com/images/home_wheat_field.jpg” cannot be displayed, because it contains errors. A Great Plains wheat field


Figure 23 (paper) summarizes 279 experiments in which plants of various types were raised under CO2-enhanced conditions. Plants under stress from less-than-ideal conditions – a common occurrence in nature – respond more to CO2 fertilization. The selections of species …… were biased toward plants that respond less to CO2 fertilization than does the mixture actually covering the Earth, so (these results) underestimate .. the effects of global CO2 enhancement.

….(T)he green revolution in agriculture has already benefitted from CO2 fertilization, and benefits in the future will be even greater. Animal life is increasing proportionally, as shown by studies of 51 terrestrial and 22 aquatic ecosystems. Moreover, as shown by a study of 94 terrestrial ecosystems on all continents except Antarctica, species richness – biodiversity – is more positively correlated with productivity – the total quantity of plant life per acre – than with anything else.

http://www.geog.ubc.ca/biodiversity/images/BiodiversityCover.jpg” cannot be displayed, because it contains errors. A neat biodiversity poster from our friends in Canada, British Columbia

(end of quotations)


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To me the most valuable contribution of this section of the paper by Robinson, et.al. is the documentation of the large number of credible scientific studies that provide evidence for increased levels of plant and animal growth on the earth during the last half century – approximately the same time period over which atmospheric CO2 levels have been increasing.

Of particular interest to someone from western Kansas such as myself is evidence that increased levels of CO2 would lead to increased wheat production in the face of dry / drought-prone crop production conditions.


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One response

3 08 2008

Thanks for the post

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