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A Project of The Annenberg Public Policy Center

How can carbon dioxide be harmful if it’s ‘plant food’?

The notion that carbon dioxide is “plant food” and that climate change is therefore a good thing or not a problem is a common refrain from those who deny the reality of climate change or who oppose reducing greenhouse emissions.

It’s true that carbon dioxide, the main heat-trapping gas that is causing global warming, is essential for plant growth. Most — but not all plants — tend to respond to increased levels of CO2 by growing more. 

But more CO2 is not always good. Many of the changes expected with higher atmospheric CO2 levels are frequently harmful to plants and crops, including drought and higher temperatures. Field experiments growing crops such as wheat and rice at increased CO2 levels have also found that the plants had less protein and B vitamins, and fewer micronutrients.

Moreover, focusing just on the possible benefits to some plants in a hotter world obscures many of the profoundly negative effects of climate change.