We can't count on plants to slow down global warming

[GliderGuider]

We can't count on plants to slow down global warming

Increased future plant growth will not reduce carbon dioxide levels in the atmosphere as much as we thought; so finds a new study published in Science. This means that we will not have that get-out-of-jail-free card that some of us were counting on.

The authors found that increased CO2 in the atmosphere actually increased the outflux of carbon dioxide from the soils. That is, it increased the rate of decomposition. In the long run, the increases in influx and outflux will essentially balance out. This suggests that there will be little help from the biosphere for us humans – plants will not take up our emissions.

The authors have two competing hypotheses behind the physical mechanisms that drive the decomposition. They told me that it is possible the plants close their stomata (the tiny pores which allow water and CO2 to pass into and out of leaves). As the stomata close, the soils become wetter and microbial activity increases. The authors also think that as atmospheric CO2 increases, soil microbes respond by decomposing older soil carbon. They call this a “priming effect” which is a natural buffering mechanism that slows carbon accumulation in soils.

[appal_jack]

1. While this is very worth studying, I suspect that this study is not the last word on the topic.

Last edited Thu May 15, 2014, 06:33 PM - Edit history (4)

While this is very worth studying, I suspect that this study is not the last word on the topic. On agricultural lands, the entire history to this point has tilted toward burning, destroying, and otherwise reducing soil carbon. Various exciting cover-cropping, reduced-tillage-organic, and soil humification strategies being pioneered by people such as the Rodale Institute offer significant tools that could help turn this trend around if widely adopted. Also, pastured systems and rotational grazing seem to significantly build soil humates over time as animals are moved over perennial polyculture meadow grounds. Then there is the bio-char work being done by Cornell University, etc. Some of the fringe-ier deep ecology types actually oppose bio-char work out of a fear that it could deplete our O2 supply if widely adopted. Naturally, I think that those people have a poor understanding of basic math, and especially orders of magnitude. But I do believe that a bio-char, cover-cropping, reduced-tillage-organic, and soil humification-centric agriculture, adopted across much of the world, could not only decrease atmospheric CO2, but also radically improve agricultural productivity and sustainability.

K&R,

-app

[Starboard Tack]

2. Heck, if we can't count on plants or humans I guess we're screwed.

Boats with air conditioning maybe.

[NickB79]

3. Fucking lazy plants!

What are they good for if they can't even fix our mistakes?

I say screw'em and pave them over. Lazy bums.

[poopfuel]

4. I asked an expert I know and he said this

"It so much depends on what the plants are, how deep the topsoil and subsoil are loosened to admit air, and what latitude they are doing the study at. Too many variables to consider and this study clearly does not. A meta study doesn’t look at details and it wasn’t done on actual soil, only in a computer. A world wide loosening of farming soil beneath topsoil would probably impound all the extra carbon dioxide i.e. making subsoil into living topsoil and thereby dramatically increasing soil biology.

Unfortunately the game is really going to be played out in the oceans."

[NickB79]

5. "A world wide loosening of farming soil beneath topsoil"

First, I'd LOVE to hear any proposal that would be able to do this in our lifetimes, because that would be a monumental undertaking.

Secondly, most research points to widespread soil aeration as a PROBLEM that is RELEASING carbon, not improving it's capture: http://www.npr.org/templates/story/story.php?storyId=11951725

"The tearing of the soil, introducing oxygen that's what tillage is all about," Burras says. "The history of civilization is tillage. I believe it was Daniel Webster who said, 'Where tillage begins, other arts follow.'"

But tillage also changes the land. Burras walks 100 feet east, out of the grass and into a field planted with soybeans. Here, once again, he turns over some soil.

"One of the most striking differences, as we look at this, is that the field is a little grayer, not quite as black," he says. "That reflects the past century of plowing and such. We've seen the organic carbon content of the field go from 5 percent to about 3 percent."

It may not seem like much, but it means that over the past 100 years, every acre of this field has vented about 50 tons of carbon dioxide into the atmosphere. That's about as much as eight average cars pump out in a year.

[cprise]

6. "A global shift in the rate of photosynthesis"

http://news.mongabay.com/2013/1122-sekar-browning-mountain-forests.html#usxUtv8pASOUwXms.99

This is about a separate (though AGW-related) effect that limits plant growth due to water availability.

[GliderGuider]

7. Interesting finding. Thanks! nt