In artifical conditions in laboratory there is a significant effect, up to 20% when doubling pre-industrial CO2 concentration.
But, in practice for wild plants nitrogen quickly becomes the bottleneck, so the real gains are much smaller.
And even for farming plants (which have fertilizer providing additional nitrogen) the real gains diminish, and are more in 5-10% range. For some crops CO2 has very little effect at all (for example corn).
Additionally - crops grew with raised CO2 levels have less proteins and useful nutrients.
And then you have to factor in the harmful effects from global warming on crops (heat damage, dry soil, less farmland available) and the overall effect is likely negative.
https://www.scientificamerican.com/article/ask-the-experts-d...
Edit funny the downvotes. I’m on your team guys! Just think we can’t ignore counter facts.
I don't think there is any risk of areas reaching temperatures too hot for any plants?
> which will reduce the length of growing season
Why?
Corn, for instance, can't grow when the temp is over 104 or so (depending on cultivar) and dies when exposed to temps over 110 or so. It maximizes its growth rate at around 86 degrees.
So: if you have a summer month when temps are regularly over 104, that's not really a growing season for corn. Thus you have to try to plant earlier and harvest earlier, and the window when you can do that successfully may be considerable shorter than it would if the temp stayed below 104 during the summer.
So then you try to go closer to the poles. But -- depending on temperatures and a lot of other factors -- that may not be a totally satisfying solution either. Corn needs specific amounts of rain, which may or may not coincide with periods when the temperatures are good. It also needs large amounts of soil nitrogen, which may or may not be present in arctic soils, and if the plant doesn't have it growth is slowed. Corn also needs the soil temperature to be relatively high to germinate (above 50 degrees, again depending somewhat on cultivar). In arctic soils, it may take a while for the soil to warm up that much in the spring, and that may reduce your growing season. So how all the factors play out, and whether those factors result in a longer or shorter growing season, are intimately connected to exactly how the climate changes.
I've used corn as an example, but of course other crops and wild plants all rely on complicated, interconnected conditions to thrive. The specifics are a bit different for every plant.
It all depends. There are a lot of factors that we won't really know until people start trying to do it.
How much is enough to matter? Will the net effect be more or less than change from CO2 or temperature? You tell me. We seem to have a lot of unknowns.
"Global warming" would be better named "wilder temperature swings" (which is why we hear the phrase "global climate change"). Larger temperature swings (colder winters, hotter summers, no real spring or fall seasons) are not good for growing crops.
It's splitting a hair, to be sure, but developing root nodules for hosting a nitrogen-fixer species is a lot easier than evolving all the biochemical precursors from scratch. Nitrogen fixation symbiosis may have evolved independently in plants at least three times. It would have been a big advantage from 460 to 380 Mya and then again, to a far lesser extent, from 240 to 160 Mya. Teredo shipworms also employ nitrogen-fixing symbionts, in their gill structures, as well as some termites, in their guts, but the latter only derive benefit in an extremely low-nitrogen environment.
Since atmospheric CO2 has dropped after the last peaks, some plant species failed to preserve that symbiosis. They would have an easier time getting it back, now that CO2 partial pressure is rising back to levels experienced in prior geological eras.
The ultimate bottleneck is likely to be iron or magnesium.
So you could spray ammonia everywhere to promote growth, but it's not clear that you'll offset the carbon emissions from making so much ammonia in the first place.
[1] https://m.phys.org/news/2018-07-electrochemically-produced-a...
nitrogen fixing cover crops is the way in agriculture I guess
That's something the geeks have still a hard time to understand. They won't convince anybody by being right. That's not how public opinion work.
It's very small effect that would take enormous spans of time to make any significant difference. Also in order for those plants to grow faster and make a difference, there needs to be a significant amount of plants. So it's a marginal issue. If plants grow at (made up number) 2% faster due to higher CO2 concentrations, that doesn't help much if we've wiped out 90% of the plant biomass.
CO2 concentrations are growing at <1% pa (year on year - there are large variations between northern hemisphere summer/winter), so an additional 2% absorbing effect from an increasing number of plants is not insignificant.
Conditions might be rarer, but the steps aren't solely reliant on the absence of microbes which now exist.
As per https://www.politico.com/agenda/story/2017/09/13/food-nutrie...
> As best scientists can tell, this is what happens: Rising CO2 revs up photosynthesis, the process that helps plants transform sunlight to food. This makes plants grow, but it also leads them to pack in more carbohydrates like glucose at the expense of other nutrients that we depend on, like protein, iron and zinc.
Unless you think that the only thing that's "good for plants" is their suitability for being eaten by humans this seems like an unrelated issue.
The vast majority of the Earth's plant biomass isn't going to be eaten by humans. You're not going to nibble on the oak tree in your back yard, but increased CO^2 in the air will make it more efficient at sequestering carbon.
It's not going to be some amazing increase in perceived growth rate. The CO^2 level indoors is often 2-3x what it is outside, and people already grow plants in those conditions.
And while more plants is certainly a nice thing, there's more to having a healthy planet than just having more plants, especially when it comes at the cost of melting ice caps and changing weather patterns, possibly leading to desertification and less plants in other places.
Although according to the article, this particular increase in greenery is mostly due to projects to plant more trees in Indian and China, and investments into agriculture. All of them good things that don't really need more CO2 in the atmosphere.
Any time a group starts altering the facts like this, it just shows that they value their 'message' above the truth, and they lose all credibility.
Edit: Downvote = disagree, or people genuinely believe it's OK to lie to further your cause, I'm not sure what's more disturbing.
In particular there's a faction of people who use "CO2 is plant food" to argue that it cannot be harmful, that reduction efforts would be wrong, etc.
And also, the whole discussion branch nearby on the greening effect of small increases in CO2 is really missing the point, and is completely ungrounded in any science. There is a whole literature out there on how significant this effect is relative to other effects of rising CO2! (Spoiler: it is not that significant.)
So you disagree with the grandparent post's statement that "But it seems this fact is usually omitted so as not to complicate the intended message."?
There are plenty of large, prominent climate activist groups making prominent public statements. I've never heard a single one of them discuss this aspect. (Contrast with scientific papers, many of which do mention it and which are not what we were talking about).
The key phrase you're looking for is: CO2 fertilization.
That sounds a lot like intentionally misleading people.