Peak Green: CO2 is Plant Food ... and why it won't save us

[Aeson]

https://advances.sciencemag.org/content/5/8/eaax1396

The short of it is, without water it doesn't matter how much CO2 there is. Plants won't grow as well. Changes in climate has lead to much of the world experience more vapor deficit. Even with greening from CO2 and warming temperate/arctic regions it's resulted in a browing overall since "Peak Green" in 1998.

This is a very dangerous feedback loop to enter. 15% of the water vapor in the atmosphere is from land based evaporation and transpiration from plants. Dry plants won't transpire as much, leading to even dryer atmospheric conditions. Dryer atmospheric conditions lead to dryer plants. Less vegetation will lead to more soil compaction from rain, more erosion from wind and rain, more UV radiation reaching the soil and killing microbial life, making it less able to receive or hold moisture or deliver nutrients. Rains will runoff more instead of soak in to be re-transpired or even evaporate. Repeat ... no rinse.

Combined with the drawing down, depletion, and salt water intrusion of aquifers, water issues are looming for much of the world. Yemen isn't a model for where we want to take this world.

[Lorizael]

Eh. If we run out we can just go grab a comet.

[Jon Miller]

What I find a little funny about Elok's comments is that it is a sure thing that they pump up animals meant for meat with artificial hormones. People argue about whether the hormones impact human health, but there is the corporate line (they are safe) and there is also the increased incidents of early puberty/etc. There is a lot of contrasting information out there but this seems like something real:

https://medicalxpress.com/news/2010-06-high-meat-diet-early-puberty.html

JM

[Jon Miller]

Note that I get preached to about the spiritual and health benefits of veganism so I am not without bias.

JM

[Jon Miller]

Somehow I posted this in the wrong thread.

JM

[Aeson]

My threads are all about trees, it's easy to get confused.

[Kidlicious]

I don't see anything about how this is having any effect on plants in the real world.

[Berzerker]

we have ample evidence a warmer world is a wetter world, the Sahara formed within the past 3 million years when ice ages began and plants dominated the world far further back in time when the world was much warmer.

locking much of the world's fresh water up in ice reduces atmospheric water vapor

[Aeson]

we have ample evidence a warmer world is a wetter world, the Sahara formed within the past 3 million years when ice ages began and plants dominated the world far further back in time when the world was much warmer.

locking much of the world's fresh water up in ice reduces atmospheric water vapor

This isn’t about the absolute amount of water vapor, but rather how much water vapor there is in relation to how much water vapor it can hold. As air temp rises, so does the amount of water vapor it can hold.

Currently the water vapor is basically not keeping up with the increase in the size of the container it’s filling, leading to reduced relative humidity and rainfall. This has overcome and reversed the greening effect of increased CO2. Thus the observed browning over recent decades.

It may be in time the water vapor would catch up. Bear in mind these magnitude of changes usually happen over much longer periods of time. It could be a very long wait.

[Aeson]

I don't see anything about how this is having any effect on plants in the real world.

Worldwide browning trend overcoming the previous greening.

[Kidlicious]

I didn't see any evidence in the report you sited. Less rain also doesn't necessarily mean less plants.

[Aeson]

I didn't see any evidence in the report you sited.

It shows how, and references other studies which also look at how VPD is affecting terrestrial vegetation.

ess rain also doesn't necessarily mean less plants.

This is about VPD, not just rainfall. In any case, a hypothetical scenario where less rainfall wouldn't lead to less vegetation just doesn't apply to the reality where there is already an observed trend of less vegetation. VPD helps to explain why this trend is occuring even in the face of the greening effect of increased CO2.