Thread: climate change and CO2 vs plants?

I know that global warming is caused by increasing CO2 in our atmosphere, but does it affect how plant work too?

As CO2 increases, I think plants would love it as they can perform photosynthesis with abundance of raw materials (the CO2), but as this trend continues with increasing CO2 and increasing temperature, will it eventually become too hot for them to survive?

And since plants are supposed to be carbon sinks, what happens to this capability when temperatures get extremely high?

Originally Posted by miwashi

I know that global warming is caused by increasing CO2 in our atmosphere, but does it affect how plant work too?

As CO2 increases, I think plants would love it as they can perform photosynthesis with abundance of raw materials (the CO2), but as this trend continues with increasing CO2 and increasing temperature, will it eventually become too hot for them to survive?

Your hunch is correct. While increased Co2 helps plants by a small amount, changes in temperature, humidity and rainfall have far more effect.
Climate myths: Higher CO2 levels will boost plant growth and food production - environment - 16 May 2007 - New Scientist

Thank you.

In the linked article it says "Increased CO2 will increase plant growth, possibly contributing further to assimilation of CO2. But higher plant growth will only lock away CO₂ if there is an accumulation of organic matter."

What is this accumulation of organic matter referring to? Does it refer to growth of biomass, ie the plant is accumulating organic matter to increase its mass?

And from the last paragraph, it does seem to say that till now there is still no definite prediction as to what the long term effect of more CO2 on plants will be?

Originally Posted by miwashi

What is this accumulation of organic matter referring to? Does it refer to growth of biomass, ie the plant is accumulating organic matter to increase its mass?

It does refer to the accumulation of biomass, but that represents only a temporary sink; a longer term accumulation or sequesteration refers to the material being deposited in the geological record. In other words, plants that serve some economic end over a monthly to decadal scale cannot be considered effective sinks; it's only if they are 'buried' and thus removed from the system.

And from the last paragraph, it does seem to say that till now there is still no definite prediction as to what the long term effect of more CO2 on plants will be?

As already noted by some studies, the mid-term effect will likely arise in current species expanding their ecological niche by developing a broader range of stomata they employ to live. With increased CO2, plants may require fewer stomata to thrive, thus not having any appreciable effect on atmospheric CO2. Over the long term - far exceeding human life spans - evolution will likely exploit increased atmospheric CO2 for an overall reduction or equillibrium.

Originally Posted by miwashi

I know that global warming is caused by increasing CO2 in our atmosphere, but does it affect how plant work too?

I'm curious.

How do you "know" that CO2 has caused global warming?

How much does the changing solar output and black carbon on the norther ice cap have to play, vs. CO2, in the global warming we have documented?

well, what I know is that CO2 is a greenhouse gas that traps heat, and the basic stuff that the UNFCCC brought up about the need to reduce it to mitigate warming effects.

I'm quite interested in the plant aspect of it as most of the media talks about the greenhouse gases on their own.

Can I summarize that these are what we can expect for longterm effects of increased CO2 on plants?

Are there any different kinds of expected responses for different kiinds of plants, or will it be a general response?



- photosynthesis level likely to increase.

- increased plant growth but limited by low nutrients (Nitrogen?) in soil. Will it be a consistent longterm response?

- decreased evaporative cooling because of the stomata changes. Leading to increased global warming.

Take a look at what happened during the Carboniferous period. Climate change decimated whole forests. Increased CO2 is conducive to higher photosynthesis levels, but the climate change the increased levels of CO2 can bring could tip the scale significantly in the other direction.

Regardless of this, the primary reason climate change is "bad" is that it could severely impact on our human civilisation. The earth and the biosphere will probably continue and change as it might, but we are trying to keep ourselves alive and kicking as much as we can.

CO2 is seldom a limiting resource for plants - it's in oversupply relative to nitrogen, or phosphorus, or water, or light, or soemthing of the kind, for almost all plants all the time.

That said, it does help in such things as reduced stomatal exhalation of water, etc, and so those plants currently limited in some way by competition from plants with better fitted arrangements in those matters can find themselves comparatively better off. Poison ivy seems to be one of those - a little extra CO2 seems to give it a competitive boost over better sun-dry adapted plants at the edges of meadows.

So does this mean that the longterm effect on climate change is still hard to preduct? That overall photosynthesis will increase in the short term, but in the decades or centuries that follow the increased photosynthesis will taper off because other nutrients limit it? And that in the long term the carbon assimilating properties of plants will also taper off, leading to even more carbon dioxide in our environment, contributing to even more global warming?

Nutrients limits might always apply, now and in the future. Changing temperature, humidity and rainfall will limit and even be the predominent factor until entire forest and other ecosystems have had time to move hundreds of miles North or climb thousands of feet in elevation--and than only in the case if things settle down. Remember the original article? Co2 +10%, water reductions -50%. What is the amount for other nutrients?

I'm guessing the other nutrients will be very much scarcer than carbon, especially the trace elements, so yes, I agree the limiting factor would be these nutrients rather than carbon.

I found this paper by Long:
http://ddr.nal.usda.gov/bitstream/10...ND43650355.pdf

He described the longest study so far in open-air rather than enclosed conditions, and mentioned that there is no evidence found of downregulating the initial spike in photosynthesis and production that come with elevated CO2.

This goes against some other literature I've seen that say this spike is transient and will go down over time.

I was wondering what is the general view of what's right in the community so far?