The levels of CO2 in the atmosphere is increasing and have done so for many years. Shouldn’t this have a positive impact on plants etc.?
Maybe not nature including humans, but plants should thrive, right?
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Just like how humans can have too much CO2, so can plants. Combine in other effects, like increased temperature, higher or lower humidity, nutrient uptake changes, and things get bad for contemporary plants with an increased CO2 level, combined with other increases. Remember, all the plants that are around, developed in a relatively stable environment with low CO2.
One of the big issues is that since the CO2 increases temperatures, we see more stomatal closures on plant leaves, and we see a decrease in evapotranspiration (releasing of water vapour). This latter part might sound like a good thing, the plants lose less water, well when plants lose water, that water turns into rain. So we see less rain falling in rainforests, because there is simply less water in the water cycle.
Increased CO2 levels also increase the thickness of the leaves. Plants with thicker leaves are worse at capturing CO2, amongst getting worse at other things.
Increased temperature also increasing the rate at which the plants respire, so they hold on to less of the CO2 than had the temperatures been lower.
If you can increase CO2 without increasing those other things, like temperature. It works out great, which is why it works in green houses. But it doesn’t represent reality.
Like others have said, it’s an incredibly complex issue that we haven’t had to deal with, so we are learning new things all the time. I only learned about the leaf thickness thing last year, and the science behind it only goes back to 2018 because that’s when we started noticing that in certain places, the leaves were getting thicker (by as much as 1/3rd), tests showed it was a reaction to increased CO2 levels and all that it brings with it.
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