More CO2 is good because it is plant food
CO2 can enhance growth of some plants in isolation, but IPCC AR6 confirms human-induced warming has already slowed global agricultural productivity and that the net effect of rising CO2 within its associated climate impacts is harmful to food security.
What we know
The CO2 fertilization effect is real and measurable. Under controlled conditions with ample water and nutrients, elevated CO2 causes faster photosynthesis in many C3 plants (wheat, rice, soybeans). Some studies show yield gains of 10 to 20 percent at doubled CO2. This is the scientific basis for the 'plant food' argument.
However, CO2 does not rise in isolation; it rises along with temperature, altered precipitation, increased extreme weather, higher ozone, and other stressors. The IPCC AR6 Working Group II (Chapter 5) found with medium confidence that human-induced warming has already reduced global crop production as a drag on growth, and estimates a net yield loss across four major crops of about 9.5 percent through 2010 when warming and ozone effects are combined with the positive CO2 effect. C4 plants (maize, sugarcane, sorghum) show much smaller CO2 fertilization benefits. Nutritional quality also declines: elevated CO2 reduces protein, zinc, and iron concentrations in staple crops.
Furthermore, forests and natural ecosystems cannot simply absorb unlimited CO2. Nutrient limitations (nitrogen, phosphorus) constrain how much additional growth is possible. The net effect of the full package of climate change, including CO2 increase, is negative for biodiversity and ecosystem function. The claim treats CO2 as a simple fertilizer while ignoring the atmospheric system it is warming.
Common claims
- Higher CO2 helps plants grow, so it is beneficialPartially true but misleading - warming, drought, and ozone offset gains
- CO2 fertilization will improve global food productionFalse at scale - IPCC finds net negative impact on crop yields
- Plants will absorb extra CO2 and stabilize the climateFalse - nutrient limitations constrain uptake; absorption is insufficient