Is global warming good for plants?

Some people deny that global warming is happening. Others agree that it is happening, but claim it isn’t a bad thing. People in this second group often say that global warming isn’t bad because all that extra carbon in the air will promote plant growth, which will benefit agriculture and the environment. Is this true?

Not really.

As described in the last post, plants do need carbon to grow, and they like having more of it around. But, they like extra carbon a little too much.

Let’s explore why by looking at humans and sugar.

Humans like sugar. We generally think of sugar as a bad and unnecessary thing that makes us fat. But, in fact, humans need sugar. In the past, sugar was rare and hard to find. Because sugar was important for human nutrition but difficult to get, evolution fitted us with a sugar craving that drives us to search energetically for this nutrient, and consume it whenever possible. This worked great until the modern age, when sugar became abundant and readily available in our dietary environment. Our biology hasn’t yet learned that it should tell us to eat a certain amount of sugar and then stop. And so, unless we manage to exert a lot of willpower, we end up eating too much sugar, and we get sick from it.

A similar mechanism is at work in plants. A plant’s biology tells the plant to absorb as much carbon as possible. This is very good for the plant as long as the amount of carbon the plant can realistically absorb is not greater than the amount of carbon the plant really needs. However, if a plant was able to absorb more carbon than it needed – for example, due to rising carbon levels in the atmosphere related to global warming – then the plant would happily gorge itself on the extra carbon. In a classic case of too much of a good thing, the plant would then become sick.

This is not just theoretical. Studies have found that plants that binge on carbon really do become unhealthy. Just like humans who eat too much sugar produce body fat that isn’t good for them, plants that absorb too much carbon produce abnormally high levels of starch. And while these plants are getting vegetatively flabby, they store less protein in their pollen.

This means that the plants are not healthy, their pollen does not contain the nutrients that pollen-eating animals need to be healthy, and the parts of the plants that humans eat are similarly lacking in nutrients that humans need to be healthy. Far from being a boon to agriculture, global warming puts plants on a junk food diet that is bad for everyone.

And that part isn’t theoretical either. Studies on how plants react to excess carbon haven’t just been done in the lab. In the US, plants living in the wild have shown a marked decrease in the protein content of their pollen since America began industrializing in the 1840s. That decline has been most severe over the past six decades, when America’s carbon emissions were increasing dramatically.

Global warming is a serious problem that we are running out of time to solve. At this point, we cannot decrease our emissions steeply enough to avoid disastrous warming on our planet. To prevent the worst impacts of climate change, we need to not only reduce our emissions, but also actively work to take carbon out of the atmosphere.

Humans have not yet invented technology that can take carbon out of the atmosphere. Fortunately, nature has. We call that technology plants.

Global warming will not benefit either humans or plants. But if humans and plants work together, we still may be able to solve this urgent problem.

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Is global warming good for plants?

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