[HillRat]

Under conditions of increased CO2 availability, plants tend to decrease waster usage and sequester more carbon. Growth rates are faster, but require increased mineral availability. Unfortunately, nitrogen levels in plants decrease in high-atmospheric CO2 conditions, which leads to lower protein concentrations. As a result, consumption crops provide less energy and nutrition when consumed.

So, all in all, the downsides outweigh the upsides -- faster growth, lower nutrition, more aggressive soil depletion, and increased water runoff. On the bright side, carbon sequestration increases up to 40%, so the efficacy of planting forests as a sequestration measure will increase.

As for biodiversity -- well, dieoffs are already outpacing speciation. Unless you believe in abiogenesis, the trendline is moving sharply downward.

[James001]

Really?

You're going to extrapolate from lower nitrogen levels in plants in higher CO2 conditions (without a citation, might i add) to higher CO2 levels causing overall lower nutrition? and more aggressive soil depletion? Keep in mind that obviously more plant growth means more plant decay which cycles back int othe ecosystem.

Are you trying to suggest that we should be decreasing agricultural yields so as to prevent soil depletion? There are better ways.

[mikeash]

"without a citation, might i add"

Odd card to play when your comment had no citations either, and you seem to be ignoring my request for them....

[James001]

It's well established that increased CO2 leads to increased plant biomass, thereby satisfying my claim that it leads to increased agricultural yield (as per greenhouses for example).

My claim that increased CO2 leads to more biodiversity is more tenuous but is more likely than a decrease in biodiversity, all other factors being controlled for.

[mikeash]

Typical double standard, your speculation is perfectly reasonable but the other guy's claims need scientific backing. Annoying, and not very convincing!

[James001]

You must have never delved too much into science then. There are certain claims that have been well established for so long that citations are no longer needed. For example, we don't need citations to state the order of colours in a rainbow. Likewise, I don't need a citation to state that plant biomass increases with a greater concentration of CO2. That's basic science, it's unequivocal and not controversial. On the other hand, the previous dude made wild speculation about increased CO2 causing increased soil depletion. I'm sorry if you don't see the difference. Not everyone is suited to being a scientist.

[mikeash]

Searching around, it looks like what you say is often the case, but is not guaranteed, and the full effects of increased CO2 concentration on real-world crops is still very much up in the air. For example:

https://www.mpg.de/6650626/carbon-dioxide-crop-yields

Sure doesn't look as simple as the order of colors in a rainbow to me.