A frequent talking point by global warming deniers is that CO2 in the atmosphere is actually beneficial because "CO2 is plant food". I'm a non biologist trying to figure out under what circumstances this is actually true.
Here are my thoughts so far:
- Plant growth is more or less governed by Liebig's law of the minimum - the plant needs sunlight, CO2, water, nutrients in a certain composition, whatever is lacking limits growth
- In addition to it's role in photosynthesis, water is needed to transport nutrients from the soil, so dry conditions can limit effective nutrient availability
- The energy needed to assimilate CO2-carbon is independent of the CO2 concentration
- The rate of photosynthesis is (within the limits given by energy etc.) governed by CO2 concentration and active plant matter
- photosynthesis only works in a more or less narrow temperature band
From this, it follows that a higher CO2 concentration in air will boost plant growth only if everything else (light, water, nutrients) is abundant.
So I have two interconnecteed questions:
- How wrong is my simplistic view, does my conclusion hold?
- What do we actually observe in the wild or in experiments?