Increased Carbon Dioxide Levels Do NOT Always Results in Good Harvest from Crops!

It's well-known that increasing Carbon Dioxide has been causing more catastrophic results on Earth, including global climate change and related effects. However, certain groups, including climate change deniers, are trying to convey to the public that increased Carbon Dioxide helps increase plants' photosynthesis, paving the way for more food production. Let’s look at such claims.

Social Media Posts

There are social media posts promoting misinformed claims about how increased Carbon dioxide levels can, in fact, be helpful in combating food insecurity in the World. This is contrary to the commonly known impacts of Climate Change. The following video talks about how concentrated Carbon Dioxide within greenhouses improves food production.

The below video talks about the concentration of Carbon Dioxide in greenhouses and food production of crops, trying to imply that the increasing Carbon Dioxide level is good for the planet Earth.

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Fact Check

The claim made in the video is merely cherry-picking on a process called CO2 fertilization. Although plants require carbon dioxide to flourish, they may not thrive in situations with high levels of carbon. Different plants react differently to increased carbon. Carbon dioxide is not the sole component responsible for the plant kingdom's growth, despite carbon enthusiasts' opinions. Plants require water, sunlight, and other minerals in the correct ratios for optimum growth.

Given how our climate changes, obtaining the basic necessities for plant growth becomes an issue. Droughts in areas like West America worsen due to climate change, decreasing the water supply and raising the risk of disastrous wildfires. Moreover, Climate Change will cause a rise in pests that prefer warmer winters, more frequent calamities like flash floods and heat stress, and rising seas exposing plants to salt water. Although the concept of planting millions more trees has been floated frequently to remove some CO2 from the atmosphere, it is unclear if the planet would have enough nutrients in the soil to support such growth.

What is CO2 fertilization?

Photosynthesis is a fundamental concept in biology: plants use sunlight to convert water and CO2 into chemically bound energy and oxygen. This process allows plants to synthesize the chemical building blocks required for growth and produces the biproducts, oxygen and food for our consumption. While sunlight is abundant, water, atmospheric carbon dioxide, and other necessary inputs are limited, limiting the scale at which photosynthesis can occur.

As previously stated, carbon dioxide can be a limiting factor in photosynthesis. Thus, in the availability of more carbon dioxide and other inputs, the photosynthesis process would be scaled up, increasing the amount of atmospheric carbon dioxide bound by plants. The result would be a slower increase in carbon dioxide concentrations in the atmosphere than expected based solely on global emissions. Furthermore, higher carbon dioxide levels in the atmosphere have been shown to increase water use efficiency, allowing plants to survive in drier conditions. As a result of these two processes, the biosphere absorbs more carbon dioxide and thus increases the land carbon stock. This phenomenon is known as the carbon dioxide fertilization effect.

CO2 boosts plant productivity, but other factors also count.

Photosynthesis occurs when plants combine sunlight, atmospheric carbon dioxide, and water to create oxygen and carbohydrates for growth and energy. The carbon fertilization effect results from increased photosynthesis caused by rising carbon dioxide levels in the atmosphere. According to a recent study, global plant photosynthesis increased by 12% between 1982 and 2020, parallel to a 17% increase in atmospheric carbon dioxide levels. This increase in photosynthesis was mainly brought on due to this phenomenon.

Plants utilize less water for photosynthesis when there is more carbon dioxide in the air. Stomata, which are openings on plant leaves, allow the absorption of carbon dioxide and transpiration, which is the release of excess water into the atmosphere. Plants can sustain a high rate of photosynthesis and partially cover their stomata when atmospheric carbon dioxide levels rise, reducing their water loss by 5% to 20%. Scientists have hypothesized that this would cause plants to retain more water on land, in soil, and in streams by releasing less water into the atmosphere.

The study discovered that the nitrogen-fixation temperature response is different from the photosynthesis temperature response, which uses nitrogen-containing enzymes. These enzymes may function less effectively at higher temperatures. Rubisco is the primary enzyme that converts carbon dioxide from the atmosphere into carbohydrates during photosynthesis. However, when temperatures rise, it “relaxes” and loses precision in the form of the carbon dioxide pocket it retains. As a result, the enzyme mistakenly fixes oxygen instead of carbon dioxide, decreasing photosynthetic efficiency and wasting the plant’s resources. Rubisco can become entirely inactive at even higher temperatures.

Richard Norby, a corporate research fellow in the Environmental Sciences Division and Climate Change Science Institute of Oak Ridge National Laboratory, says, “If you isolate a leaf [in a laboratory] and you increase the level of CO2, photosynthesis will increase. That’s well established.” However, he goes on to add that results produced inside laboratories are not what exactly happens in the more vastly complex world outside. He explains that many factors also contribute to this process, and for example, “If nitrogen is limited, the benefit of the CO2 increase is limited…. You can’t just look at CO2 because the overall context really matters.” More on this here

Here is another study by NASA that states that “Rising Carbon Dioxide Levels Will Help and Hurt Crops.”

Current trends and projections on the CO2 fertilization effect

Whether photosynthesis is increased due to increased atmospheric carbon dioxide levels or weakened due to higher temperatures – and, for that matter, the general development of the land carbon sink – is a question that depends on a plethora of interactions that science is attempting to answer using observations, field experiments, and computer models. The fertilization effect appears to be still at work (between the years 2000 and 2009, approximately 14 gigatonnes of CO2 equivalent were additionally absorbed per year compared to the pre-industrial era in 1750), though, at a slower rate: the rate at which photosynthesis is enhanced is declining in comparison to the rate at which carbon dioxide is released into the atmosphere. The photosynthetic process will be slower in the future, according to predictions, as we go from a fertile to a warming-dominated time. In this scenario, plants cease to operate as a sink for carbon dioxide, reducing global warming, and instead become a source of carbon dioxide emission that causes temperatures to rise more quickly.

While some agricultural yields may improve, the amount of critical nutrients in crops is impacted by rising carbon dioxide levels. According to one study, the protein content of potato tubers, wheat, rice, and barley grains fell by 10% to 15% due to increased carbon dioxide. Essential minerals, including calcium, magnesium, phosphorus, iron, and zinc, are also lost by crops. According to a study done on different rice varieties in 2018, elevated carbon dioxide levels enhanced vitamin E while lowering vitamins B1, B2, B5, and B9.

Along with increasingly frequent droughts and heat waves, climate change is predicted to harm the carbon fertilization effect. While agricultural yields typically decline during hot growing seasons, the interaction of heat and dryness may result in maize yields reducing by 20% in some US regions and by 40% in Eastern Europe and southeast Africa. In areas where crop yields are expected to rise due to warmer temperatures, such as the northern US, Canada, and Ukraine, the combination of heat and water constraints may also lower crop yields.

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Conclusion

Based on our investigation, the claim mentioned above is only a half-truth. In unmanaged forests, fields, and other ecosystems, plant growth is influenced by various other factors. Hence, we need to consider the overall impact of each component before coming to a plausible conclusion. The Physiology of plants will require all these necessary components in a ratio, and if exceeded, it can do more harm to the plants and, in turn, those that depend on it.