What percentage of atmospheric CO2 is best for plants?

[Xist]

It's life Jim, but not we know it.

[aerohead]

Originally Posted by Xist

While we have discussed atmospheric CO2 levels in a ridiculously long thread immediately abandoned by its creator, somehow I did not realize that CO2 is measured by parts per million, not percentage.
I read elsewhere that too much carbon dioxide makes water acidic and plants may not create oxygen fast enough for their own needs. I also read that more CO2 will help plants grow, but without increasing other nutrients, they will be deficient.
This page states "Ambient levels of CO2 hover around 400-500 ppm. When you increase that level to around 1,000-1,500 ppm, you will see an increase in your yields and your plants will be much healthier." https://www.maximumyield.com/what-ar...ying-it/7/2610

Is this science fair material?

I'll make a stab :
CO2 is considered fertilizer to plants.
Increased CO2 will increase crop yields,however CO2 does not discriminate between plants,and while crops grow,so do weeds.And more herbicides($) may be required per acre to control unwanted weeds,and the increased chemicals may exceed established thresholds for exposure.
Temperature is another animal.
Rice yield declines from higher night time temps.
El Salvador has lost 90% of its coffee crop due to elevated temps,along with 2,500 dead cane cutters over the last two decades,who experienced renal failure on the job,unable to remain hydrated in the increased heat.
In 2002 Canada saw a 5% drop in their wheat harvest due to temps.
In 2003 record heat in Europe cut production 90-million tonnes,and killed 52,000 people,in 9-countries.
In 2005 the U.S.Corn Belt saw a shortfall of 34-million tons.
In 2010 Russia lost 40% of it's wheat,leading to banned exports,food prices soared, which sparked the Arab Spring.56,000 people died in the heat wave,smog,and wildfires.
Pine beetle northern migration meant tree kills leading to lightning-triggered wildfires in the U.S..

[Xist]

Dr. Kei Mori filtered out ultraviolet and infrared light. He was confounding variables, but Aerohead, it seems like that would benefit everyone you mentioned, although I cannot imagine how it would be executed outside of a greenhouse.

[aerohead]

In a November,2015 National Geographic,pp.90-92,'Crop Changes',from,International Food Policy Research Institute and UN Food and Agricultural Org.:
*Climate change is likely to be most forgiving of wheat,but not enough to offset losses from other major crops.
*Midwestern US 20% drop in corn production.
*More pests for mid-elevation potato-growing areas.
*Brazilian farmers will see a 16% decline.
*N.European potato farmers see longer growing season,while farther south will become increasingly dry.
*New areas will open up for corn,but yields will decline in existing areas.
*It may be possible to grow potatoes farther north or higher in mountains.
*Rice may do well.
*Virtually all climate scenarios show reduced wheat yields,more devastating crop diseases.
*West Africa may support more rice.
*Indonesia's rice will be largely spared,but corn will decline as much as 20%.
*New parts of Australia will become arable,but droughts will require efficient farming if growing wheat is to continue.
*Yields of crops like soybeans could increase,but soybean and barley nutritive content may be less.

[gone-ot]

Originally Posted by aerohead

I'll make a stab :
CO2 is considered fertilizer to plants.
Increased CO2 will increase crop yields,however CO2 does not discriminate between plants,and while crops grow,so do weeds.And more herbicides($) may be required per acre to control unwanted weeds,and the increased chemicals may exceed established thresholds for exposure.
Temperature is another animal.
Rice yield declines from higher night time temps.
El Salvador has lost 90% of its coffee crop due to elevated temps,along with 2,500 dead cane cutters over the last two decades,who experienced renal failure on the job,unable to remain hydrated in the increased heat.
In 2002 Canada saw a 5% drop in their wheat harvest due to temps.
In 2003 record heat in Europe cut production 90-million tonnes,and killed 52,000 people,in 9-countries.
In 2005 the U.S.Corn Belt saw a shortfall of 34-million tons.
In 2010 Russia lost 40% of it's wheat,leading to banned exports,food prices soared, which sparked the Arab Spring.56,000 people died in the heat wave,smog,and wildfires.
Pine beetle northern migration meant tree kills leading to lightning-triggered wildfires in the U.S..

The University of Arizona scientists at Bio Sphere 2 claim 800 ppm CO2 is the limit above which rain-forest plant growth ceases and death/decay begins to accelerate.

[aerohead]

From: 'Will Plants Profit From High CO2?',by Elizabeth Culotta,Science,VOL.268.5 May 1995,pp.654-6
*CO2 is an aerial fertilizer
*in experimental,single-variable,CO2 enrichment,the higher concentration 'may' help many crops grow faster,increase yields.
*in 'natural ecosystems',the effects are less clear.
*hundreds of questions about what happens to the rest of the forest,soil microbes to poison ivy.
*CO2 can affect virtually every aspect of the structure and function of terrestrial ecosystems-from flowering times to microbial activity,species diversity.
*not all plants react the same way:with either a C3 or C4 carbon pathway.
*without added water,light,pest control,fertilizer,CO2 doesn't necessarily help plant growth.
*CO2's affect on insects,weeds,livestock unpredictable.
*High CO2 can mean low nitrogen leaf area,less protein for livestock
*High CO2 doesn't guarantee good biodiversity.
*Plants in natural ecosystems don't always respond to high CO2 the way crops do.
*Photosynthesis levels off over time.
*tundra returns to pre-CO2 level growth after 6-weeks.
*trees level off after 6-weeks
*during wet years prairie grass grows no better.
*in the past 100-years up to 10% of increased crop yields have come from higher CO2 rather than new crop varieties,fertilizers and insecticides.
*CO2 long term,less nitrogen in leaf litter = less available nitrogen to plant
*estimated global response to a 2X increase in CO2 = 10-20% growth increase.
*Plants will not be able to balance the carbon budget.
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Also,
from:'A Clearer View of Why Plants Make Haze,' by Christine Mlot,plant biologist,Science,VOL.268,5 May 1995,pp.641-42.
*Heat increases the production of bio-hydrocarbon VOCs,mostly Isoprene,which when combined with BBQ/tailpipe emissions of Nitrogen Oxides,create ground level ozone (NOx) in the presence of sunlight,which destroy pulmonary tissue for those breathing it, and create nitric acid vapor at the water's surface of lakes.
*The warmer it gets,the more plants produce it,as they attempt to protect their host chlorophyll,which without isoprene gives out at 37-degrees C.

[redpoint5]

Crop yields have trended upwards for years over the decades, but that's a poor indicator of the impact of CO2. However, it's probably a good indicator of the ingenuity of humans, so whatever happens, we're likely to adapt well to the changes, and I forsee improving standards of living for the world at least through the next hundred years.

The oceans rose about 8" along with temperature and CO2 during this timeframe, similar to what is projected for the next 100 years.

[freebeard]

*CO2 can effect virtually every aspect of the structure and function of terrestrial ecosystems-from flowering times to microbial activity,species diversity.

effect ≠ affect.