https://theconversation.com/rising-carbon-dioxide-is-making-the-worlds-plants-more-water-wise-79427And from the CSIRO's own website
https://blog.csiro.au/rising-carbon-dioxide-making-worlds-plants-water-wise/Land plants are absorbing 17% more carbon dioxide from the atmosphere now than 30 years ago, our research published today shows. Equally extraordinarily, our study also shows that the vegetation is hardly using any extra water to do it, suggesting that global change is causing the world’s plants to grow in a more water-efficient way.
Water is the most precious resource needed for plants to grow, and our research suggests that vegetation is becoming much better at using it in a world in which CO₂
...
Increasing carbon uptake typically comes at a cost. To let CO₂ in, plants have to open up pores called stomata in their leaves, which in turn allows water to sneak out. Plants thus need to strike a balance between taking up carbon to build new leaves, stems and roots, while minimising water loss in the process. This has led to sophisticated adaptations that has allowed many plant species to conquer a range of arid environments.
One such adaptation is to close the stomata slightly to allow CO₂ to enter with less water getting out. Under increasing atmospheric CO₂, the overall result is that CO₂ uptake increases while water consumption does not.
e.g. there isn't a necessary link "using more CO2 means you need more water". Point one is therefore a pure assumption with questionable validity.
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2. Unlike Nature, our way of agriculture does not self-fertilize by recycling all dead plants, animals and their waste. Instead we have to constantly add artificial fertilizers produced by energy-intensive processes mostly fed by hydrocarbons
But point #2 would seem to apply to
any agriculture, whatsoever, not necessarily specific to an increase in production related to CO2.
Also, how we make the fertilizer doesn't mean that we can't get the
increase. e.g. more crops = need more fertilizer = more emissions from fertilizer production. But none of those things "prove" that we can't get the increase in the first place.
3. Too high a concentration of CO2 causes a reduction of photosynthesis in certain of plants.
Yeah "certain plants". Unfortunately, for that hypothesis, so-far, there's been a fairly linear increase in plant growth
generally in line with increased atmospheric CO2. So, point not proven to be relevant. Some plants like CO2 more than others, and on the whole, more plants grow with more CO2. The fact that they need to specify
certain plants here is the giveaway: it's not a true statement for "plants in general" or they would have said so.
4. As is confirmed by long-term experiments, plants with exhorbitant supplies of CO2 run up against limited availability of other nutrients. These long term projects show that while some plants exhibit a brief and promising burst of growth upon initial exposure to C02, effects such as the "nitrogen plateau" soon truncate this benefit
Yeah, but we
have plants and microbes that actively fixate nitrogen into the soil, such as legumes. The experiment which "proved" that nitrogen was the limiting factor was conducted under laboratory conditions with a mono-culture of grass plants.
Standard plant food you’d pick up at the store is rich in nitrogen, potassium and phosphorous, each a necessary fuel for plant growth. So even with a bursting supply of carbon dioxide, no nitrogen means no growth.
Ok, so more growth won't happen because nitrogen is a limiting factor. But that contradicts the study they use to prove the next point:
5. Plants raised with enhanced CO2 supplies and strictly isolated from insects behave differently than if the same approach is tried in an otherwise natural setting. For example, when the growth of soybeans is boosted out in the open this creates changes in plant chemistry that makes these specimens more vulnerable to insects, as the illustration below shows.
Go look at the study: the study showed that the high-CO2 plants lacked nitrogen, and the bugs ate more so that they could get enough nitrogren. e.g. that proves that the "nitrogen limit" isn't so cut-and-dried as point #4 was trying to make: soybeans compensate by using less nitrogen when more CO2 is available, e.g. they grow more plant mass per unit of nitrogen than otherwise.
Also, the study was done by putting bugs on each type of plant and seeing how much they eat. The bugs eat more of the nitrogen-poor plants. But that doesn't "prove" that they're attracted to those plants. e.g. imagine if you did a lab experiment with two humans where you put one in a room with calorie-dense food and another in a room with calorie-poor food, and you note that the person with the calorie-poor food
eats more food. You
can't then conclude that humans are "attracted" to the calorie-poor food just because the person with
no choice ate more of it. e.g. if the soybean crops are poor in nitrogen, as a result of growing more via CO2 absorption, and this isn't a fate shared by wild plants, maybe the bugs will piss off and prefer eating weeds to the nitrogen-starved soybeans? also, since the bugs are trying to get a certain
amount of nitrogen, and the soybeans are no longer optimal for that, there's no real reason to expect that the extra soybeans they eat will exceed the additional growth.
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