Climate Change: Plants Choke on too Much Carbon

It looks like even for plants, there can be too much of a good thing. Trees and flowers use carbon dioxide (CO2) to make energy, absorbing the gas to help fuel the process of photosynthesis. For this reason, some experts have theorized that rising carbon levels will eventually promote plant growth. Now, new research claims that this assumption is dead wrong.

That's at least according to a study recently published in the journal Global Change Biology, which details how the plants in a number of very different ecosystems appear to actually suffer from too much atmospheric carbon.

Sample crops, grasslands, and forests all seemed to lose some ability to absorb nutrients when exposed to rising CO2 levels in large-scale field experiments held in eight countries across four continents.

"The findings of the study are unequivocal. The nitrogen content in the crops is reduced in atmospheres with raised carbon dioxide levels in all three ecosystem types," Johan Uddling, a researcher with the University of Gothenburg, said in a statement.

"Furthermore, we can see that this negative effect exists regardless of whether or not the plants' growth increases, and even if fertilizer is added. This is unexpected and new," he added. (Scroll to read on...)

The study found that both wheat and rice are already suffering from heightening carbon levels - a phenomenon (both man- and nature-driven) that has been frequently described as impossible to stop.

The decline of wheat in particular has already been associated with a climbing global temperature, which can be blamed on climbing greenhouse gas levels.

However, other studies have shown that spiking carbon levels beyond everyday standards can be very good for forests, with several free-air CO2 enrichment (FACE) experiments all showing that more carbon means deeper roots and growing forests. Larger forests, it was assumed, would then serve as a stronger carbon sink, limiting how high greenhouse gas levels can rise.

Unfortunately, according to Uddling and his team, there is a lot of danger in just assuming everything will simply find a balance.

It's been theorized that rising CO2 levels in the atmosphere are somehow having a diluting effect, impeding how much nitrogen - essential for plant protein production - is carried into soil. Past research has found that if plants get all the right growing conditions, but not enough nitrogen, they will quickly outpace their own energy supplies. (Scroll to read on...)

You could liken this to taking a healthy pre-teen, and then locking up the kitchen right when he begins to go through a growth spurt - a cruel fate for any young refrigerator raider.

Of course, in the case of fields and forests, this comes with consequences much more serious than a middle-schooler in a foul mood. The plants will quite literally grow to death, often withering long before the growing season ends.

However, Uddling adds that even this explanation is too simple.

"We are seeing reduced nitrogen content even when growth has not been affected," he explained. "Moreover, the effect is there in trials with powerful fertilizer, which indicates that it is not down to limited access to nitrogen in the soil. Future studies should look at what is causing the effect, but it appears to be linked to plants' capacity to absorb nitrogen rather than to changed levels in the soil."

The takeaway? Plants are more complicated than even scientists like to believe, and how climate change and its factors will impact them is still very much a mystery asking to be solved.

For how warming will likewise be less helpful for plant-life than initially thought, check out our last article on the subject here.

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