Carbon Dioxide: The Green Greenhouse Gas of Life (and ‘miracle molecule’)
“CO2 is also a pollution fighter that reduces the harmful effects of ozone, nitrous oxides and other pollutants in the air, or too much nitrogen fertilizer in the soil.”
It’s amazing that minuscule bacteria can cause life-threatening diseases and infections – and miraculous that tiny doses of vaccines and antibiotics can safeguard us against these deadly scourges.
Equally astounding, trace amounts of selenium in our bodies protect us against the harmful effects of methylmercury. Just as incredible, this same element added to a manmade formula helps ensure that musk oxen calves survive their first year of life in an Alaskan wildlife conservation area where soils and thus forage are so deficient in selenium that their mothers’ milk cannot nourish them adequately.
It may thus not be too surprising that, at the planetary level, carbon dioxide is a miracle molecule for plants – and the “gas of life” for most living creatures on Earth. 
In units of volume, CO2’s concentration is typically presented as 400 parts per million (400 ppm). Translated, that’s just 0.04% of Earth’s atmosphere – the equivalent of 40 cents out of one thousand dollars, or 1.4 inches on a football field. Even atmospheric argon is 23 times more abundant: 9,300 ppm.
Moreover, the 400 ppm in 2013 is 120 ppm more than the 280 ppm carbon dioxide level in 1800, and that two-century increase is equivalent to a mere 12 cents out of $1,000, or one half-inch on a football field.
Eliminate carbon dioxide, and plants would shrivel and die. So would lake and ocean phytoplankton, grasses, kelp and other water plants. After that, animal and human life would disappear. Even reducing CO2 levels too much – sending them back to pre-industrial levels, for example – would have terrible consequences for crops, other plants, animals and humans.
The dawn of the nineteenth century marks the time when our planet finally began its fitful emergence from the Little Ice Age that had cooled the Earth and driven Viking settlers out of Greenland. Many scientists say plants were comparatively starved for carbon dioxide during that chilly era.
Rising CO2 Levels
Atmospheric levels of CO2 have risen from approximately 280 ppm pre-industrial to nearly 400 ppm today.
Over the past two centuries, warming oceans released some of the carbon dioxide stored in their waters. Beginning with the Industrial Revolution, factories and growing human populations burned more wood and fossil fuels, baked more bread, and brewed more beer, adding still more CO2 to the atmosphere.
Much more of the miracle molecule came from volcanoes and subsea vents, forest fires, biofuel use, decaying plants and animals, and “exhaust” from living, breathing animals and humans. El Niño events warmed sea waters, causing them to exhale huge amounts of CO2 into the atmosphere. (La Niña events cool waters and cause them to absorb more carbon dioxide.)
What a difference that extra 120 ppm has made! What a difference even higher CO2 concentrations exert on plants, and thus on animals and humans that depend on them.
The more carbon dioxide there is in the atmosphere, the more it is absorbed by plants of every description – helping them to grow faster, better, and even under adverse conditions like limited water, extremely hot air temperatures, or infestations of insects and other pests.
As trees, grasses, algae and crops grow faster and become healthier and more robust, animals and humans enjoy better nutrition on a planet that is greener and greener. CO2 is also a pollution fighter that reduces the harmful effects of ozone, nitrous oxides and other pollutants in the air, or too much nitrogen fertilizer in the soil.
Of the more than seven billion people on Earth today, over a billion are malnourished, with insufficient protein and energy in their diets; even more suffer from micronutrient deprivation. This is causing growing tension between the need for land to feed humans better – and the need to keep land in its natural state to support plants and wildlife.
How well we handle this challenge of increased crop production from the same or less acreage may mean the difference between global food sufficiency and rampant human starvation in coming decades – and between the survival and extinction of many plant and animal species.
Modern agricultural methods – mechanized equipment, hybrid seeds, synthetic fertilizers, insecticides, improved irrigation methods, biotechnology, the use of hot houses for growing specialty crops, and other advances – dramatically improved crop yields per acre between 1930 and today. That is especially important as millions of acres of farmland are being diverted from food crops, and millions of acres of rainforest and other wildlife habitat are being plowed under, for biofuel production.
Studies in Greenhouses
Carbon dioxide also plays a vital role. Increased CO2 levels in greenhouses dramatically improve plant growth, especially when inside temperatures are also elevated – and rising atmospheric carbon dioxide levels have likewise had astounding positive impacts on outdoor plant growth and survival.
As a general rule, a 300 ppm increase in CO2 improves the productivity of herbaceous plants by 30-50% and of woody plants by 50-80%. Many plants respond even better. For example, lentils, peas and other legumes grown with 700 ppm carbon dioxide improved their total biomass by 91%, their edible parts yield by 150 % and their fodder yield by 67%, compared to similar crops grown at 370 ppm carbon dioxide, Indian researchers found.
Chinese scientists calculated that rice grown at 600 ppm CO2 increased its grain yield by 28% with low applications of nitrogen fertilizer. U.S. researchers discovered that sugarcane grown in sunlit greenhouses at 720 ppm CO2 and 11 degrees F higher than outside ambient air produced stem juice an amazing 124% higher in volume than sugarcane grown at ambient temperature and 360 ppm carbon dioxide. Non-food crops like cotton also fare much better when carbon dioxide levels are higher.
Other researchers found that tree and rice species survived, and even continued growing, under conditions of drought or prolonged submergence in water, if the air had high carbon dioxide levels. Still other studies determined that desirable crops actually fare better against intrusive weeds, when CO2 levels are higher.
Research into natural forest and crop growth during recent periods of rising atmospheric carbon dioxide levels, between 1900 and 2010, found significant improvements under “real-world” conditions, as well.
An analysis of Scots pines in Catalonia, Spain showed that tree diameter and cross-sectional area expanded by 84% between 1900 and 2000. The growth of young Wisconsin trees increased by 60%, and tree ring width expanded by almost 53%, as atmospheric carbon dioxide concentrations rose from 316 ppm in 1958 to 376 ppm in 2003, researchers calculated.
University of Minnesota scientists compared the growth of trees and other plants during the first half of the twentieth century (which included the terrible Dust Bowl years), when CO2 levels rose only 10 ppm – to the period 1950-2000, when CO2 increased by 57 ppm. They found that reduced sensitivity to severe drought improved plant survival rates by almost 50%. Swiss researchers concluded that, because of rising carbon dioxide levels, “alpine plant life is proliferating, biodiversity is on the rise, and the mountain world appears more productive and inviting than ever.”
Other researchers used actual historical (real-world) data for land use, atmospheric CO2 concentration, nitrogen deposition, fertilization, ozone levels, rainfall and climate – combined with their knowledge of plant physiology and growth – to develop a computer model that simulates plant growth responses for grasslands, forests, wetlands and agriculture in the southern United States from 1895 to 2007. They determined that “net primary productivity” improved by an average of 27% during this 112-year period, with most of the increased growth occurring after 1950, when carbon dioxide levels rose the most, from 310 ppm in 1950 to 395 ppm in 2007.
These and numerous other studies confirm that continued CO2 enrichment of Earth’s atmosphere will increase per-acre yields worldwide – and ensure that more people have access to greater quantities of more nutritious food, while reducing impacts on wildlife and their habitats.
CO2 at Work
Plants use energy from the sun to convert carbon dioxide from the air, and water and minerals from the soil, into carbohydrates and other molecules that form roots, stems, leaves, seeds and “fruits.” The process is aided by catalytic action from an enzyme called RuBisCO, the single most abundant protein in leaves and probably on Earth. RuBisCO plays a key role in carbon fixation, the process plants use to convert carbon dioxide into glucose and other carbohydrates that build plant structures.
More CO2 means more and larger flowers; higher seed mass and germination success; and improved plant resistance to droughts, diseases, viruses, pathogenic infections, air pollutants, and salt or nitrogen accumulation in soils. It improves the ability of plants to utilize water, soil nutrients and fertilizer.
Higher CO2 levels also improve plants’ water use efficiency – ensuring faster and greater carbon uptake by plant tissues, with less water lost through transpiration. More airborne carbon dioxide lets plants reduce the size of their stomata, little holes in the leaves that plants use to inhale carbon dioxide building blocks. When CO2 is scarce, the openings increase in size, to find and capture sufficient supplies of this “gas of life.” But increasing stomata size means more water molecules escape, and the water loss places increasing stress on the plants, eventually threatening their growth and even survival.
When the air’s carbon dioxide levels rise – to 400, 600 or 800 ppm – the stomata shrink in size, causing them to lose less water from transpiration, while still absorbing ample CO2 molecules. That enables them to survive extended dry spells much better.
Abundant CO2 also increases the biomass, numbers and total surface area of lateral roots and fine-roots, enabling plants to absorb more water and soil nutrients, and obtain sufficient phosphorus even when it is in short supply in soils. Carbon dioxide also stimulates nitrogen fixation, helping plants to form stronger symbiotic relationships with nitrogen-fixing soil bacteria, further increasing photosynthetic rates.
A Grim (Less) CO2 Future
One of the worst things that could happen to our planet and its people, animals and plants would be for carbon dioxide levels to plunge back to levels last seen before the Industrial Revolution. Decreasing CO2 levels would be especially problematical if Earth cools, in response to the sun entering another “quiet phase,” as happened during the Little Ice Age.
If Earth cools again, growing seasons would shorten and arable cropland would decrease in the northern temperate zones. We would then need every possible molecule of carbon dioxide – just to keep agricultural production high enough to stave off mass human starvation … and save wildlife habitats from being plowed under to replace that lost cropland.
However, even under current Modern Warm Era conditions, crops, other plants, animals and people will benefit from more carbon dioxide. The “gas of life” is a miracle plant fertilizer that helps land, lake, river and ocean plants to grow and prosper, greening the planet, nourishing wildlife habitats, feeding people who crave larger bounties of more nutritious food, and preventing species loss.
The positives of this colorless, odorless, tasteless gas that comprises just 0.04 percent of our atmosphere abound. We should praise carbon dioxide – not vilify, ban or bury it. CO2 is both an enabler of life and a sign of man’s escape from poverty to modern times.
 Documentation for this post comes from the 2009 and 2011 volumes of the Nongovernmental International Panel on Climate Change report, Climate Change Reconsidered (particularly the chapter here), as well as Dr. Craig Idso’s www.CO2science.org website summarize hundreds of similar studies of crops, forests, grasslands, alpine areas and deserts enriched by carbon dioxide. For more studies on the effects of carbon dioxide, see CO2 Science’s Plant Growth Database.
Paul Driessen’s full report on the magic and mystery of CO2 can be found at www.CFACT.org.