Higher CO2 Concentrations Mean Better Plant Water Use, Enhanced Photosynthesis, Expanding Sahel

William Astley’s comment on CO2 and photosynthesis has been upgraded to a post (subheadings added). 

Rich green North German park. Photo by P. Gosselin 

Higher CO2 concentrations offer even more advantages

By William Astley

Better water use by plants

In addition to increasing crop yields, increased CO2 enables plants to live in regions were there is sparse rainfall. C3 plants (trees, cereal crops, and shrubs) lose roughly 50% of the water they absorb due to trans-respiration (loss of water from the plant’s stomata which are holes in the leaves to let in CO2). When CO2 rises C3 plants produce less stomata which reduces the water loss in the plant. This results in more water at the root of the plant which enables synergistic bacteria on the roots to produce more nitrogen byproducts which increases plant growth.

A higher level of atmospheric CO2 enables plants to make more effective use of water and enables the plant to survive in regions of low rainfall such as deserts.

Ontario, Canada Ministry of Agriculture, Food, and Rural Affairs
Carbon Dioxide In Greenhouses

Enhanced photosynthesis

The benefits of carbon dioxide supplementation on plant growth and production within the greenhouse environment have been well understood for many years

For the majority of greenhouse crops, net photosynthesis increases as CO2 levels increase from 340–1,000 ppm (parts per million). Most crops show that for any given level of photosynthetically active radiation (PAR), increasing the CO2 level to 1,000 ppm will increase the photosynthesis by about 50% over ambient CO2 levels.

The level to which the CO2 concentration should be raised depends on the crop, light intensity, temperature, ventilation, stage of the crop growth and the economics of the crop. For most crops the saturation point will be reached at about 1,000–1,300 ppm under ideal circumstances.


Greenhouse Gas Might Green Up The Desert; Weizmann Institute Study Suggests That Rising Carbon Dioxide Levels Might Cause Forests To Spread Into Dry Environments

…..However, the Yatir forest is growing at a relatively quick pace, and is even expanding further into the desert.

Expanding sahel

The green shoots of recovery are showing up on satellite images of regions including the Sahel, a semi-desert zone bordering the Sahara to the south that stretches some 2,400 miles (3,860 kilometers). Images taken between 1982 and 2002 revealed extensive regreening throughout the Sahel, according to a new study in the journal Biogeosciences.


6 responses to “Higher CO2 Concentrations Mean Better Plant Water Use, Enhanced Photosynthesis, Expanding Sahel”

  1. Higher CO2 Concentrations Mean Better Plant Water Use, Enhanced Photosynthesis, Expanding Sahel – Climate- Science.press

    […] Higher CO2 Concentrations Mean Better Plant Water Use, Enhanced Photosynthesis, Expanding Sahel […]

  2. Richard Greene

    The first link is from 2002
    The second link is from 2003
    The third link does not work
    Such old links are less persuasive
    than recently published material

    Those links are pitiful considering there are thousands
    of studies with almost all showing CO2 enrichment increases
    plant growth and reduces fresh water requirements.

    The benefits of greenhouse CO2 enrichment was claimed to
    have been known for many “years” It would have been more
    accurate to write many “decades”.

    And although a typical goal is from 800 to 1500ppm CO2
    inside greenhouses, there is no 1000ppm magic number
    as the article implies.

    Much better links to summaries
    of CO2 enrichment scientific studies:



    FULL REPORT: (1078 page pdf)


    1. William Astley

      Thanks for your comments Richard and your links.

      Here is another link that supports the same position. Increased CO2 enables C3 plants that grow in regions where there is inadequate rainfall, to reduce the number of stomata on their leaves to reduce water loss.

      It is interesting that the recent warming has caused on increase in rainfall in the largest desert in the world, not a decrease. During the warmest part of this interglacial when the planet was 2C to 5C warmer, the Sahara desert was a savannah with large lakes.

      Warming has caused increased rainfall in the Sahara and Sahel deserts.

      The Sahel is greening

      “However in sharp contrast to this gloomy outlook, it seems that global warming has exactly the opposite effect on the Sahara and the Sahel. The Sahara is actually shrinking, with vegetation arising on land where there was nothing but sand and rocks before.4”

      “There are now more trees, more grassland for livestock and a 70% increase in yields of local cereals such sorghum and millet in recent years. Vegetation has also increased significantly in the past 15 years in southern Mauritania, north-western Niger, central Chad, much of Sudan and parts of Eritrea.5 In Burkina Faso and Mali, production of millet rose by 55 percent and 35 percent, respectively, since 1980.6 Satellite photos, taken between 1982 and 2002, revealed the extensive re-greening throughout the Sahel.7 Aerial photographs and interviews with local people have confirmed the increase in vegetation.8”

      …Rising atmospheric CO2 levels also have an antitranspiration effect, which enhances the water-use efficiency of plants and enables them to grow in areas that were once too dry for them.17 “

      “When the Sahara was a savannah
      The greening of the Sahara and the Sahel is not unprecedented. During the Holocene Climate Optimum (9000-4000 BC… were possibly 2-5 degrees Celsius warmer than now, the northern half of Africa received more abundant and more stable rainfall. What is now the Sahara desert was a green savannah then.”

      1. Richard Greene

        The old links you used can make readers wonder if there has been data mining. Deliberately not showing the past 20 years because an older trend had changed.

        NASA Earth Data
        compiles a Vegetation Index
        reflecting greening on our planet,
        measured from satellites.

        NASA Vegetation IndexL
        Data are at the link below,
        made difficult to access,
        probably deliberately.


        One researcher– Zoe Phin — downloaded the data
        and created a good chart one year ago:

        Copernicus Global Land Service
        has a Leaf Area Index:

        CO2 Science Website Archive:
        There is a huge database of brief summaries of CO2 plant studies I used to read every day. The new content died off a few years ago (maybe the website owner retired or died? ). But he left behind an archive of well written short articles:

        Climate Discussion Nexus:
        Some of the old articles are reproduced,
        almost one every week, at the following
        Canadian website

        Concerning plant stomata:
        The number will eventually evolve lower in a CO2 enriched environment. But there is also a short term response to CO2 enrichment. The stomata stay open for a shorter periods of time to get the needed CO2, reducing transpiration.

        While C3 plants almost universally benefit from CO2 enrichment, C4 photosynthesis plants can benefit too.

        I have read perhaps 100 studies of CO2 enrichment over the past two decades. Unfortunately, not that many were concerning C4 plants. But the C4 results were consistently positive with CO2 enrichment, even if not as great as C3 plants.

        Patrick Moore, Ph.D. has included the benefits of CO2 enrichment many times in his climate science papers. A good summary of his climate science knowledge is at:

        Hope these links are useful for you.
        It’s refreshing to see others interested
        in the benefits of CO2.
        Rather than in the usual always wrong
        wild guesses of the future climate doom.

  3. Larry DeVries

    Yes, another benefit of CO2. The warmists have contrived the phrase “cost of carbon” calculation as a negative replacing the molecule with the dirty word “carbon”. The skeptics need a catch phrase such as “benefits of the carbon dioxide module”, define it, and use that phrase often. Especially as it applies to food production.

  4. Weekly Climate and Energy News Roundup #497 – Watts Up With That?

    […] Higher CO2 Concentrations Mean Better Plant Water Use, Enhanced Photosynthesis, Expanding Sahel […]

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