What about the forests?

Question

What will the impact of GW be on the three major types of forest (tropical, temperate, and boreal)? Won't a warming trend expand both the temperate and boreal forests, creating a larger carbon sink than what we have now? I keep getting answers about how this is all taken into account on the models, but is it, really? Isn't this just the sort of thing that one or two little assumptions in the model will drastically influence the results? Is it too far out of the realm of possibility to think that the side of the argument that sets the parameters on the models might fudge things just a tiny bit to make things seem worse than they might very well be?

Isn't this just another example of the inherent inaccuracy of modeling something like climate, trying to quantify things like expanded plant growth vs. release of stored greenhouse gases, when it is at best an estimate, at worst sheer speculation?

Answer 1

I would think forests would start growing in polar regions where there is only tundra now. But forests do not take any significant amount of CO2 out of the air permanently because each tree will die some day and release all its stored CO2 back into the air. Permanent sequestering of CO2 requires coral or shell fish or something that stores CO2 in limestone and not wood.

Answer 2

The AGW loonies would never admit to it, but yes, a warmer climate would be greatly beneficial to veggies. Also, the increase in CO2 would be excellent for plant growth.

Answer 3

Say goodbye to them it was nice while they were here.

Answer 4

I would think that the most immediate impact on forests by global warming will be the inundation (by water) of lowland areas which may be forested.  Large population centers will have to leave lower elevations and that will put more strain on the remaining resources.  Areas of tundra in arctic regions are not going to warm sufficiently to allow for forestation or agriculture.

Answer 5

1. Rising CO2 levels increases the acidity of rain, negatively affecting plant growth and survival:

http://www.killerinourmidst.com/P-T%20bo...

"As a greenhouse gas, it warms the atmosphere, changing ecological conditions. (Deccan Traps volcanism, coming before the end of the Cretaceous, is estimated to have warmed the world by 3° to 5°C, or 5.4° to 9°F; Ravizza and Peucker-Ehrenbrink, 2003.) And because it combines chemically to form carbonic acid, it also produces mildly acidic rain. Acid rain can dissolve calcium carbonate shells, particularly those at or near the ocean surface.  Additionally, acid rain leaches vital nutrients from the soil, resulting in plant stunting and death."

2. Pests can thrive, seriously affecting the survival of some plant species:

Climate Change and Bark Beetles

http://66.218.69.11/search/cache?ei=UTF-...

Thresholds in the life cycle of the spruce bark beetle under climate change

http://necsi.org/events/iccs6/viewpaper?...

3. Warming is forecast to increase the frequency and magnitude of droughts and desertification:

Steven Chu, a Nobel laureate and the director of the Lawrence Berkeley National Laboratory, one of the United States government’s pre-eminent research facilities, remarked that diminished supplies of fresh water might prove a far more serious problem than slowly rising seas.  Chu noted that even the most optimistic climate models for the second half of this century suggest that 30 to 70 percent of the snowpack will disappear. “There’s a two-thirds chance there will be a disaster,” Chu said, “and that’s in the best scenario.”

http://www.nytimes.com/2007/10/21/magazi...

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You have not substantiated your case for expanded plant growth or considered some of the obvious negative outcomes of warming and CO2 increase, so your conclusion that global warming and CO2 increase will be beneficial to plants is, to use your own words, is "at best an estimate, at worst sheer speculation".

Answer 6

You may be right,  but by the time the boreal forest moves down into the U.S. and becomes a big enough carbon sink, well who knows...

It's not as if trees can migrate.

Answer 7

I'm no expert here, but I suspect that the forests will only expand if the rain patterns allow it.  Global warming will likely cause significant shifts in rain patterns, and areas that currently sustain forests may be not too warm, but rather too dry to expand.  

Also, soil conditions in areas that will be warm enough may not be sufficient to support some kinds of trees.  It's possible that if the rain in a particular area increases, and the soil becomes boggy, it could smother out the roots of some species that live there now.

edit - on re-reading the question, I realized that you were not really as interested in the possible consequences on forests  as in pointing out the inherent inaccuracies in models.  Again, I'm not the expert in modeling, but it's my understanding that the Earth is a tremendously complicated place.  Models, to be practical, have to have limits set, and poorly designed models set unrealistic limits.  However, it is an area of study that has made tremendous strides, and they appear to be taking more and more of the complexity into account.  

In life, most things are at best an estimation. Will the marriage work?  I hope so; I'll do my best to see that it does; if neither of us get sick then probably, and so on.  What's the expression?   If you want guarantees, buy a microwave.