Is increased carbon dioxide good for trees?

One of the climate change denialist memes is that, since plants inhale carbon dioxide and exhale oxygen during the day, then increased CO2 will be *good* for trees. Setting aside the facts that increased desertification and increased coastal flooding are decidedly *not* good for trees, a recent study suggests that it more CO2 doesn’t necessarily result in more/faster tree growth:

“Why not? Our new research, published today in Nature, shows it comes down to a below-ground battle for phosphorus, a mineral nutrient in soils that is essential for tree growth. The results suggest in some parts of the world, increased CO₂ means tiny bugs in the soil “hold onto” their phosphorus, making less available for trees.”


“Most Australian soils are naturally low in phosphorus, because they are derived from ancient, nutrient-depleted rocks. The same is true for most soils in tropical and subtropical regions. That makes the phosphorus service provided by microbes even more important.

“We sampled phosphorus in all parts of the ecosystem, tracing its journey from the soil to the trees. We found under high-CO₂ conditions the microbes keep more of the phosphorus they produce, to aid their own metabolism. This left less available for trees to take up.

As the article notes, the study was done in an area that is naturally low in phosphorus. How generalizable this is will have to be tested in other areas. Meanwhile, forests in South America are been cut down to make way for agriculture, and forests in Canada are burning because of global warming.

more CO2≠more tree growth