Contrary to claims online, the use of carbon dioxide (CO2) supplementation, a practice that consists of adding CO2 to a greenhouse to enhance photosynthesis and boost plant growth, is not evidence that increased levels of CO2 in the Earth’s atmosphere are environmentally friendly.
Experts consulted by Reuters concurred that the suggestion is misleading, as it oversimplifies the scientific understanding of ways in which CO2 affects climate.
“If carbon dioxide is so bad for the planet, why do greenhouse growers buy CO2 generators to double plant growth?” reads a headline of a 2013 article, which has been reshared as a screenshot on social media in July 2022.
One iteration of the screenshot on Twitter has had more than 4,000 retweets as of the writing of this article (here). Facebook posts with the claim are also viewable (here here here).
“Seems to me that all these climate fools have forgotten basic ‘science’,” one Twitter user said (here).
“But to tell a climate freek is liking talking to a brick....,” another one wrote ( here ).
Other users commenting and sharing the claim allude to climate change being a “hoax” or a “scam” (here) (here) (here).
The 2013 article was originally posted to a website ( here ) that has previously shared misleading information addressed by Reuters (here here here) and other fact-checkers (here) (here)
In the piece, the writer says CO2 “is not bad for the planet” and highlights an advertisement for CO2 generators, noting they are used in greenhouses to enhance plant productivity.
NOT THE WHOLE PICTURE
Greenhouse growers do use CO2 generators to boost plant yield, and rising CO2 concentrations in the Earth’s atmosphere – caused in large part by human influence (here) - have indeed contributed to increased photosynthesis (here) (here). This is known as the carbon fertilization effect.
However, this alone does not mean that continually increasing CO2 levels in the Earth’s atmosphere are overall healthy for the planet.
According to Kevin Griffin, Professor at the Department of Ecology, Evolution and Environmental Biology at Columbia University, it would be “unwise” to extrapolate the use of CO2 generators in greenhouses to CO2 in the natural world.
“Probably the most important response here is to disentangle the direct effects of CO2 on photosynthesis from the effects of CO2 on the climate, and then the indirect effects of climate on plant growth,” he told Reuters via email.
He explained that as well as increasing photosynthesis, CO2 also contributes to increasing climate temperatures – a potentially sought after result for specific plants kept in greenhouses during specific seasons, but a problematic outcome when applied to the entirety of planet Earth.
Trevor F. Keenan, scientist in the Climate and Ecosystem Sciences Division at Lawrence Berkeley National Laboratory, echoed Griffin’s comments, adding that the suggestion made in the article was “misleading”.
“It focuses only on one effect of CO2 (the increased productivity of plants), while ignoring another major effect (the warming of the Earth), which leads to many issues for life on the planet, including heat stress and drought impacts on plant productivity,” he said.
PHOTOSYNTHESIS
Moreover, plants only benefit from additional CO2 when the atmospheric levels of CO2 are out of balance with other factors that are vital to the photosynthesis process, such as solar power and water ( here )( here ).
When CO2 is the factor limiting plant growth, plants will respond well to increasing CO2 concentration, as it will therefore increase the rate of photosynthesis.
“So in a greenhouse where plants are well watered and well fertilized, elevating the CO2 around the plants can efficiently increase production,” Griffin said – “and that’s why folks that grow tomatoes in greenhouses buy CO2 or CO2 generators.
“However, in natural ecosystems, CO2 is often not the most limited resource (water, nutrients, temperature, or other variables are more likely limiting) and in these cases, elevated CO2 does not stimulate growth.
Griffin added: “So, if a greenhouse manager has no water to keep their plants alive, they are unlikely to buy CO2.”
According to the U.S. National Oceanic and Atmospheric Administration (NOAA), the global average of CO2 reached a record high in 2021, at 414.72 parts per million (here). Natural sinks, like forests and oceans, are estimated to have absorbed about half the CO2 emitted into the atmosphere between 2011 and 2020 (here)
In 2021, the Intergovernmental Panel on Climate Change (IPCC) concluded that it is “unequivocal that human influence has warmed the atmosphere, ocean and land” and that “widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred” ( here ).
Reuters has previously addressed other social media posts that reject mainstream climate science (here here here here) or the impact of human activity in it ( here here)
VERDICT
Misleading. Carbon dioxide does boost plant growth, but this alone does not mean increased CO2 concentration in Earth’s atmosphere is good for the environment.
This article was produced by the Reuters Fact Check team. Read more about our work to fact-check social media posts here .

Source: Reuters

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