# How did plants adapt to $\small\sf{CO_2}$ levels past 400k years? Why won't they do it again?

(Description from climate.nasa.gov: This graph, based on the comparison of atmospheric samples contained in ice cores and more recent direct measurements, provides evidence that atmospheric $$\small\sf{CO_2}$$ has increased since the Industrial Revolution. (Credit: Vostok ice core data/J.R. Petit et al.; NOAA Mauna Loa CO2 record.))

I'm not sure where and why has all $$\small\sf{CO_2}$$ gone every 100.000 years and out of where has $$\small\sf{CO_2}$$ come?

But if $$\small\sf{CO_2}$$ came from burning trees or volcanoes and disappeared because plants adapted then I have this question:

Plants somehow tolerated these 100.000 year $$\small\sf{CO_2}$$ changes over time which is very evolutionary small time. So perhaps adaptation was just about changing plants' composition percentages which is very flexible. When some rare $$\small\sf{CO_2}$$ eating trees came to be more frequent. But if that's true why can't plants change their composition again to adjust for human $$\small\sf{CO_2}$$-emissions pace?

• The variations you are looking at are the transitions from glacial to interglacial periods and not to do with the evolution of plants, thought to be initiated by Milankovic cycles (en.wikipedia.org/wiki/Milankovitch_cycles). – Dikran Marsupial Mar 5 '16 at 17:03
• The extra CO2 in the modern era comes - obviously! - from burning fossil fuels - notice the steep upward spike at the right of your graph?. The problem is not the effect of the CO2 on plants, it's that (among other things) the warming caused by the extra CO2 will raise temperatures to the point where photosynthesis shuts down. See e.g. commons.wikimedia.org/wiki/… – jamesqf Mar 5 '16 at 18:38
• One of the issues concerning CO2 & Nature's ability to deal with it is, yes, humans are putting a lot of CO2 into the atmosphere but we are limiting Nature's ability to remove the CO2 by replacing forests with urban sprawl & farms lands. – Fred Mar 6 '16 at 0:57
• Plants love CO2 - it's their limiting factor in photosynthesis, and through a few hoops, growth. All else equal, adding more CO2 makes (most) plants grow faster. It's just that the increases in CO2 concentration in the atmosphere are too tiny for that. By the time they get to useful concentrations, the plants are going to die from the extra heat :D – Luaan Mar 9 '16 at 15:53

I'm not sure where and why has all CO2 gone every 100.000 years and out of where has CO2 come?

The amount of CO2 in the atmosphere for the last 400000 years is very strongly correlated with temperature.

Temperature change (blue) and carbon dioxide change (red) observed in ice core records.
Image source: https://www.ncdc.noaa.gov/paleo/globalwarming/temperature-change.html.

Glaciations currently occur at roughly one hundred thousand year intervals, driven primarily by Milankovitch cycles. So what causes the strong correlation between temperature and carbon dioxide levels? The primary reason for this marked correlation is that carbon dioxide dissolves in cold water much more readily than it does in warm water.

As a glacial period starts, the oceans gradually get colder worldwide as ice gradually spreads over the Northern Hemisphere. This enables oceans to absorb carbon dioxide from the atmosphere. Atmospheric CO2 drop as a glaciation proceeds. The plot shows that both temperature and CO2 levels drop rather slowly over the course of a glaciation, and then both rise rather quickly as the glaciation ends.

One reason for this is atmospheric carbon dioxide levels. The Milankovitch cycles triggers the end of a glaciation. The warming oceans cannot hold as much carbon dioxide as they could during the depths of the glaciation and release carbon dioxide to the atmosphere. This exacerbates the warming, releasing even more carbon dioxide into the atmosphere. This makes the escape from a glaciation much steeper than the entry into one (Shakun 2012). A nice graph from the cited paper:

Upper plot: CO₂ concentration (yellow circles), global temperature (blue), and Antarctic temperature (red).
Lower plot: Simulation results that show that Southern Hemisphere temperatures tends to lead but global temperatures tend to lag CO₂ levels.
Image source: http://www.nature.com/nature/journal/v484/n7392/fig_tab/nature10915_F2.html.

But if CO2 came from burning trees or volcanoes and disappeared because plants adapted then I have this question:

Plants somehow tolerated these 100.000 year CO2 changes over time which is very evolutionary small time. So perhaps adaptation was just about changing plants' composition percentages which is very flexible. When some rare CO2 eating trees came to be more frequent. But if that's true why can't plants change their composition again to adjust for human CO2-emissions pace?

Your question is a bit moot since the increases in CO2 did not come from burning trees or volcanoes and did not disappear because plants adapted.

Jeremy Shakun, et al., "Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation," Nature 484.7392 (2012): 49-54.

• Thank you, this explains much! So it seems that plants are responsible only for compensation of volcanic CO2 emissions which are relatively even – A. Candy Mar 6 '16 at 0:00
• @A.Candy -- That would depend on how large the volcanic eruptions are. Current thinking is that extremely large volcanic eruptions, "large igneous provinces", are responsible for five of the mass extinction events, including the end of the dinosaurs. (The concept that it was an asteroid is a bit passé. An asteroid couldn't have caused that.) That asteroid could however have triggered a second and much larger phase of an ongoing large igneous province event, the second half of the Deccan Traps. The extinction of the dinosaurs was a 1-2-3 punch, with punch #2 being the Chicxulub impactor. – David Hammen Mar 6 '16 at 1:46
• I'm not sure plants are responsible even for that, I suspect it is the weathering of silicate rocks that largely balances the COs from volcanos on very long time scales. If there is more CO2 in the atmosphere, temperatures increase, which increases the rate of weathering (rain breaking down the rock into soluble mineals and washing them through rivers to the sea), which brings the CO2 down again. Similarly low co2 -> cooler temperatures ->less weathering -> CO2 builds up again. At least that is how I understand it. – Dikran Marsupial Mar 6 '16 at 14:21
• Incidentally, if you look at the Mauna Loa record, you will see that even large volcanic eruptions leave barely a trace on atmospheric CO2, so unless there is a "supervolcano" there really isn't much extra CO2 for the plants to react to. – Dikran Marsupial Mar 6 '16 at 14:23
• @David Hammen: Though at least by some theories, it wasn't CO2 directly from the Siberian eruptions (or their other effects) that was responsible for the Permian-Triassic extinction event, but the fact that they set fire to a large coal measure. As such, it's about the best paleontological parallel to current human fossil fuel use. – jamesqf Mar 6 '16 at 18:49

The main factors a plant consider are:

• Temperature (it is important the number of chill hours the plant receives by year).
• Luminosity (related with Milhankovic Cycles and climate of Pleistocene in general).
• Availability of soil and water (related with ice covered surface).

The main change between Pleistocene's glaciar/interglaciar for plants is there is new surface to colonize. As ice retreives, ecological succession starts. Non soil lands and permafrost is gradualy replaced by soil, so grass, other plants, and termophyllous trees start to colonize the new environments, while Coniferous and other Perennial Plants get restricted. Palinologists find this succession is relatively quick in geological time terms, taking only some decades or centuries (Roucoux, K. H. et al, 2001).

This is true for all intereglaciars. Thermophilus taxa as Gramineae or Artemixia, and grassland in general colonize new ecological niches (Branch, N. P. et al, 2015).

This is specialy true at Holocene, where the displacement of cold taxa trees by grassland and other thermophyllous phyllums could became a prelude to Holocene's antrophologic agriculture (Hillman, C., 1996).

Pleistocene $$\small\sf{CO_2}$$ levels are lower at Pleistocene than at most of Earth's History, as shown in this graph:

Source: Wikipedia. From Gradstein et al.,2005

This leads to think plants are adaptated to higger $$\small\sf{CO_2}$$ levels than Pleistocene has had and have. This is in fact true, $$\small\sf{CO_2}$$ levels are practically the lower known on Earth's History and plants have adaptated theirselves to Earth's environment with higger concentrations.

Increasing $$\small\sf{CO_2}$$ levels at Cannabaceae makes them grow more. Plants are bigger and grow faster with the same amount of ligth and nutrients. Some cultivators use $$\small\sf{CO_2}$$ superlevels to make their indoor cultives more efficient. Photosynthesis become more efficient.

Cannabis Sativa endures until 1500 ppm., where $$\small\sf{CO_2}$$ become toxic:

Source: ilovegrowingmarijuana.com

Both graphs are related. What is shown is thermophyllous plants are adapted non to Pleistocene CO2 levels but for Mesozoic / Tertiary ones. It would be interesting to know the tolerance for perennial plants and common Mesozoic ferns.

So $$\small\sf{CO_2}$$ has increased by human factors, but as temperature has not done it a lot yet and the Earth stays at the same point on Milhankovic Cycles, the only change that happens sensu lacto because of $$\small\sf{CO_2}$$ emissions on Kingdom Plantae is a bit more of efficency on photosynthesis and a bit more of landmass to colonize close to North Pole.

Nicholas P. Branch, Lionello Morandi (2015). "Late Würm and Early-Middle Holocene Environmental Change and Human Activities in the Northern Apennines, Italy". Università di Macerata, Dipartimento di Scienze della formazione, dei beni culturali e del turismo, Sezione di Beni Culturali, piazzale Bertelli 1, 62100 Macerata, Italia

Hillman, C. (1996). "The origins and spread of agriculture and pastoralism in Eurasia". UCL Press. ISBN-10 1857285379, 1857285387

Gradstein, FM, JG Ogg and AG Smith (2005) "A geologic time scale 2004", Cambridge University Press ISBN 0521786738

• Note Pleistocene CO2 levels are lower than usual at Earth's History, despite we are a cold specie and cc creates troubles, but plants were here when dinos were doing their wrongdoings :) – user12525 Jan 7 '19 at 0:01
• I find fascinating that some plants grow better with 1200 ppm of CO$_2$. Thanks for bringing that graph and study up! Cheers – Camilo Rada Feb 24 '19 at 3:32
• @CamiloRada This one comes from Himalaya, so I guess it is not one of the most thermophyllous ones. I have not that data but cereals should tolerate similar or higger levels. Also Mesozoic ferns may tolerate Pangea/Rodinia +2000 levels. – user12525 Feb 24 '19 at 9:13

Have a look at the distribution of all carbon on earth and maybe it will tell you something. Carbonaceous rocks all created in a marine environment account for 99.95% of all carbon on earth (some 100 million billion tons). The next largest source is in fact the current oceans with approximately 0.038% of the total and finally we get to fossil fuels with 0.01%. It should be noted here that there is almost 4 times more carbon dissolved currently in ocean water than there is in all fossil fuels existing on Earth. The next source would represent non marine plants and soil at 0.002% and finally our atmosphere that currently contains.0008%. So, marine environments roughly contain 99.99% of all carbon on earth and they would have you believe that there is some sort of “delicate” balance between the atmosphere and the oceans. Let’s face it the oceans of the world are and will always be the greatest carbon sink on earth.

• -1 The Question is about changes in atmospheric CO2 in the past 400K years. – Keith McClary Jun 30 '19 at 3:54

Temperature and a alkaline soil with ph level over 7,Salinity and the suns radiation is a guarantee and the dew collected every morning is all most plant life needs to survive. Co2 is not even a factor. The Earth has lost all its Co2 plenty of times and the plants thrive along with the microbes to start life over.

• To quote another member who commented elsewhere, "You are definitely not correct." – David Hammen Mar 7 '16 at 10:24