CO2 levels, happy plants and global warming

TwoBlueDay asks:

So, I hear about this increase in the carbon dioxide level in the atmosphere, allegedly caused by us humans. What I want to know is: since plants like carbon dioxide, is the earth’s plant life (the portion we don’t whack down) going to enjoy a period of vigorous and happy growth beyond what we have been used to? (I actually read an article last summer saying poison ivy was going to be very happy with the new conditions–is it alone?). The obvious corollary question is: will the plants exhale more oxygen, thus keeping things nice?

Ahh, if only it was as simple as all that….. The rise in CO2 levels is only the tip of hte global warming iceburg. This is a topic that will have to move into more than one post, so for now, I’ll write about just the CO2/O2 and plant bit.

The plants will be “happier” with a bit of extra CO2. To them, having a bit of extra COs is like having a it of extra oxygen (O2) to us. Of course, as the plants increase their metabolism, they will also increase their O2 output. I don’t know about the details of how Poison Ivy will react, but in general, all green plants should enjoy the benefits of hacing some extra CO2 around. Of course, this isn’t open ended, as there are a nnumber of other things needed for plant metabolism, and whatever is inthe shortest supply will limit the metabolic rate. That means that if a plant lives someplace that is marginal becuase of soil conditions, water availability, or pretty much anything, increasing the available CO2 won’t make any difference – the plant is restricted by something else.

Some other results of the extra CO2 are not so good for the plants. The reulting increases in temperature (what the press calls global warming) will also have an effect on plants. Plants have certain conditions that they like. If a plant is living someplace that is about as warm as the plant can stand, and it gets warmer, the plant will suffer. This can result in major changes in the foliage that lives in a particular area. Some real examples of concerns regarding changes to plant population include the NorthEast forests, and the grain fields of hte Great Plains.

The NorthEast hardwood forests have a few environmental requirements. They need winters so that the trees have a dormant period. If the temperatures do not drop below a certain point, and stay there for a certain amount of time, the hardwoods will die. Most people think that the results of a climate change would be for the forest to simply “shift” further north to an area where the temperatures are a better match, but things don’t realy work that way. recent research has shown that some of the trees will”move” north with the climate change, but the forest as a complete ecosystem will not. Think about it – the forest ecosystem includes hundreds (or thousands) of plants, insects, animals, bacteria, etc. If a subset of that library of organisms disapears, the entire ecosystem needs to adjust to the change. Similarly, if an organism (or group of organism) invades a new territory (moves north), it wil disrupt the ecosystem that is there. Wha really happens when this type of displacement occurs is that both ecosystems change, and two new ecosystems are created.

Of course, when the ecosystems adjust, there are always organisms that cannot survive in the new ecosystems, and they disapear. Another thing that happens in a disturbed ecosystem is htat lots of hybridization occurs. Organisms that have never been exposed to eachother are suddenly sharing their living space, and interbreeding occurs. This can lead to new species being formed. Of course, in a a changing ecosystem there will also be new ecological niches to fill, and the organisms will have the opportunity to allow natural selection to also encourage speciation. If left to itself, a disturbed set of ecosystems will slowly establish a new equilibrium, and establish new stable ecosystems.

The Great Plains are another example that have rather different impacts on people. While there are a number of ecosytems in the Great Plains, the one that plays the biggest role in peoples lives is the “mega-farm” ecosystem. this is a highly managed ecosystem that is maintained by a combination of natural processes and human modification. Many of the environmental models for Global Warming predict that the great plains will be experienceing droughts that will be very similar to the dustbowl droughts of the 30s. Imagine what would happen to the US and world economy if the mega-farms that grow wheat, corn, and other grains suddenly stopped producing. While the ;arge grain companies can do a lot to hybridize desired traits into plants (like drought tolerance) there is only so far a crop can be pushed. If there isn’t enough water, yields will drop, and eventually, the plants just plain old won’t grow. The rice famines in china and other parts of Asia could end up being pretty minor compared to a multi-year failure of America’s grain crops. Of course, this is just a model, and the models are always being modified and updated. Also, they are not always right – think about your weather report, which is based on models that are not all that differrent from the Global warming models. They only get the details right about 50% of the time…..

So, I guess the short answer is that the plants will be happier in the short run, but in the long run, expect change.

2 Responses to “CO2 levels, happy plants and global warming”

  1. mrschili Says:

    This leads into a question I was planning to ask (feel free to work this into another “Ask Dr. Science” question if you prefer): I’ve always been under the impression that this earth has experienced a great many climactic shifts in her lifetime. In the not too distant past (relatively speaking), most of the world was under a lot of ice. There is geological evidence that the climate we have now is NOT the climate that our ancient ancestors had. This past winter was NOT the warmest on record, nor was last spring the wettest (at least, not around here). Didn’t it SNOW in JULY in New England in the 1800’s?

    While I understand and agree that humans are having a largely detrimental effect on our environment, doesn’t the earth go through cycles and shifts all on her own anyway?

  2. sphyrnatude Says:

    Hi mrschili…


    -Dr. Science

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