Plant Productivity
As is generally taught in most second or third grade science class, atmospheric CO2 is a colorless, odorless, tasteless gas. What is more, plants just love CO2. Why? Far from being a pollutant, CO2 is better than the best fertilizer ever invented, because it is actually the "food" that sustains essentially all plants on the face of the earth. It is the primary raw material utilized by plants during the process of photosynthesis to build and construct their tissues. And the more CO2 plants "eat" (take in from the air during photosynthesis), the bigger and better they grow, a fact that has been conclusively demonstrated in literally thousands of laboratory and field experiments.

Typically, a 300-ppm increase in the air's CO2 content, which increase is expected to occur by the end of this century, raises the productivity of most herbaceous plants by about one-third; and is generally manifested by an increase in the number of branches and tillers, more and thicker leaves, more extensive root systems, and more flowers and fruit. Figure 1 presents a visual demonstration of such growth-enhancing effects on Pigeonpea (Cajanus cajan), an important legume crop grown in equatorial and semiarid parts of the world for its rich protein content. Both plants in the figure were grown under identical conditions, with the exception of atmospheric CO2 content. The plant on the left, which was grown at a CO2 concentration 20% below that to which the plant on the right was exposed, is clearly deficient in the amount of leaf, stem, nodule and root biomass it was able to produce.

Figure 1. Growth differences (total plant size, stem thickness, nodule size and number) at the time of harvest of piegonpea (Cajanus cajan) plants grown under ambient (390 ppm) or elevated (550 ppm) atmospheric CO2 concentrations.

On average, a 300 ppm increase in atmospheric CO2 enrichment leads to yield increases of 15% for CAM crops, 49% for C3 cereals, 20% for C4 cereals, 24% for fruits and melons, 44% for legumes, 48% for roots and tubers and 37% for vegetables. The growth response of woody plants to atmospheric CO2 enrichment has also been extensively studied, where reviews of numerous individual woody plant experiments have revealed a mean growth enhancement on the order of 50% for an approximate doubling of the air's CO2 content, which is about one and a half times as much as the response of herbaceous plants. Figure 2 illustrates this phenomenon in pine trees grown in normal air and air enriched with an extra 150, 300 and 450 ppm of CO2.

Figure 2. Eldarica pine trees growing in open-top chambers in 1989 at the U.S. Water Conservation Laboratory in Phoenix, AZ, under ambient air and air enriched with an extra 150, 300 or 450 ppm CO2.

Although much less studied than terrestrial plants, many aquatic plants are also known to be responsive to atmospheric CO2 enrichment, including unicellular phytoplankton and bottom-rooted macrophytes of both freshwater and saltwater species. Hence, there is likely no category of photosynthesizing plant that does not respond in a positive manner to atmospheric CO2 enrichment and that is not likely to be benefited by the ongoing rise in the air's CO2 content.

So what does the growth-enhancing benefit of atmospheric CO2 enrichment portend for the biosphere? One obvious consequence is greater crop productivity, and many researchers have acknowledged the yield-enhancing benefits of the historical and still-ongoing rise in the air's CO2 content on past, present and future crop yields. Table 1 lists the expected mass gains for the top 45 crops that account for 95 percent of total global food production in response to a 300 ppm increase in the air's CO2 content. These projected biomass increases will significantly enhance global agricultural production and help meet future food needs, where without rising CO2, global food production is expected to outstrip global food demands by mid-century.

Table 1. Mean percentage biomass enhancements produced by a 300-ppm increase in atmospheric CO2 concentration for the top 45 crops accounting for 95 percent of total global food production. Source: Idso, (2013).

In terms of economic impact, the CO2-induced stimulation of global agriculture over the past five decades has been calculated at over $3.2 trillion. And projecting the monetary value of this positive externality forward in time reveals that it will bestow an additional $9.8 trillion on crop production over the next five decades (see Figure 3). As amazing as this estimate sounds, it may very well be vastly undervalued.

Consider, for example, the fact that rice is the third most important global food crop, accounting for 9.4% of global food production. Based upon data presented in the CO2 Science Plant Growth Database, the average growth response of rice to a 300-ppm increase in the air's CO2 concentration is 35.5%. However, a team of researchers who studied the growth responses of 16 different rice genotypes, reported CO2-induced productivity increases in those genotypes that ranged from near zero to a whopping +263%. Therefore, if countries learned to identify which genotypes provided the largest yield increases per unit of CO2 rise, and then grew those genotypes, it is quite possible that the world could collectively produce enough food to supply the needs of all of its inhabitants, staving off the crippling food shortages that are projected to result in just a few short decades from now in consequence of the planet's ever increasing human population.

Considering these several benefits, it should come as no surprise, therefore, that the father of modern research in this area - Dr. Sylvan H. Wittwer - has stated that "it should be considered good fortune that we are living in a world of gradually increasing levels of atmospheric CO2," and that "the rising level of atmospheric CO2 is a universally free premium, gaining in magnitude with time, on which we can all reckon for the future."

For supporting information on this topic, click on the several links below.

CO2 Science Plant Growth Database:
An ever-expanding archive containing thousands of results from peer-reviewed scientific studies reporting the growth responses of hundreds of different plants to atmospheric CO2 enrichment. Results are tabulated according to two types of growth response (Dry Weight and Photosynthesis) and are listed alphabetically by common and scientific names.

The Positive Externalities of Carbon Dioxide: Estimating the Monetary Benefits of Rising Atmospheric CO2 Concentrations on Global Food Production:
Provides a quantitative estimate of the direct monetary benefits conferred by atmospheric CO2 enrichment on both historic and future global crop production. The results indicate that the annual total monetary value of this benefit grew from $18.5 billion in 1961 to over $140 billion by 2011, amounting to a total sum of $3.2 trillion over the 50-year period 1961-2011. Projecting the monetary value of this positive externality forward in time reveals it will likely bestow an additional $9.8 trillion on crop production between now and 2050.

Estimates of Global Food Production in the Year 2050: Will We Produce Enough to Adequately Feed the World?:
Government leaders and policy makers should take notice of the findings of this important analysis of the world food situation; for doing what climate alarmists claim is needed to fight global warming will surely consign earth's human population to a world of woe, while doing next to nothing in terms of altering the current warm phase of the planet's surface temperature.

CO2 Enhancements to Agriculture:
Scroll down this page and click on the numerous links under the heading of Agriculture to read numerous reviews of peer-reviewed science articles linking higher levels of atmospheric CO2 to increased crop productivity.

CO2 Enhancements to the Terrestrial Biosphere:
Scroll down this page and click on the numerous links under the heading of Biospheric Productivity to read numerous reviews of peer-reviewed science articles linking higher levels of atmospheric CO2 to increased plant productivity throughout the terrestrial biosphere.

To What Do We Owe the Origin of Agriculture?:
It is no surprise that rising atmospheric CO2 plays the key role here.

The Debt We Owe to Atmospheric CO2 Enrichment:
Without the increase in biomass and plant water use efficiency rising CO2 provided the "founder crops" of early agriculture, none of us would likely be here today.