Rising CO2 Will Not Benefit Plants Overall

In response to a familiar climate change skeptic argument that an increase in carbon dioxide will help plants, experts say negative impacts will outweigh any positive ones

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Some climate change skeptics argue that an increase in atmospheric carbon dioxide will benefit plants because they depend on it to photosynthesize, or make food. According to a Scientific American article, experts conclude that if carbon dioxide levels around a single isolated leaf were increased, photosynthesis rates would indeed rise. For plants in the real world, however, the gas’s negative impacts would largely outweigh any benefits.

Carbon dioxide is not sufficient for plants to photosynthesize; they also need nitrogen, which is typically in short supply. So merely raising carbon dioxide levels will not indefinitely increase photosynthesis rates for wild plants. Because it is found in fertilizers, nitrogen is not as limiting for agricultural crops. But scientists have found that crops grown at higher concentrations of carbon dioxide become less nutritious—losing iron, zinc and, in the case of grains, protein. By mid-century some researchers predict the rise in carbon dioxide in the atmosphere could impact food crops enough to cause protein deficiency in 150 million people and zinc deficiency in 150 million to 200 million people.

But perhaps the most overlooked point in this argument is that carbon dioxide drives climate change, resulting in droughts and heat stresses that wreak havoc on plants themselves.

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