"Our greatest responsibility is to be good ancestors."

-Jonas Salk

Tuesday, April 26, 2011

CO2 fertilization

Regarding encouraging plant growth, that is a direct CO2 effect. Interestingly, I just learned that it is killing koalas. You see, CO2 fertilized plants put more of their energy into structure. Eucalyptus leaves become harder for present day koalas to digest because they are more fibrous.

The person I heard this from (a world renowned ecologist) suspects that many food plants may become more fibrous and harder to digest. So the CO2 fertilization effect is not obviously a win for us fauna.

In general, rapid change in the environment is bad for niche species and good for pests. That is why the concept of "degraded ecosystem" makes sense.

Now picture ever increasing disruption everywhere...

Image: New Zealand Herald, at the first link above.


Anonymous said...

Effects of elevated CO2 on grain yield and quality of wheat: results from a 3-year free-air CO2 enrichment experiment
Högy et al. (2009) Plant Biology


I've collected a few a papers on the subject. CO2 as plant food means little when we look at the nutrient content following CO2 enrichment and other effects resulting from climate change.

The thing that really bugs me, however, is that the same people on about "CO2 is plant food" are the same characters who condone deforestation. It's nothing but excuses to maintain business as usual.

Steve Bloom said...

It was one of the very early denialist memes, originating IIRC with Sherwood Idso (who had been some sort of plant scientist) ~1990. The Idso clan has been makiing a living off coal money ever since.

Dol said...

Skeptical science just did a thorough post on this (including a Koala-related comment.)

EliRabett said...

Well, thee and me can always chew on Tom Fuller's leg.

manuel moe g said...


Too fibrous. The braincase is soft and yielding, however, with a durian-like aroma.

isaacschumann said...

Wouldn't CO2 enrichment also allow the plant to divert more energy to making toxins to defend itself as well? I remember a study done with poison ivy that found this, I would assume it to be true for plants in general.

Oale said...

isaacschumann: it's more like the plants will divert the excess CO2 to anything they can, sometimes it is toxins but mostly harmless compounds and the stem height (competition of light) or thickness (trees of sufficient height). but yes some plants can become more toxic. and other less nutritious by weight.

(will we see 'safe strains' of some foodplants?)

Greg said...

While this is bad news for some herbivore species, and while the whole "CO2 is plant food" meme is misleading, a little more fiber in the diet would be a good thing for most people eating a typical western diet.

Michael Tobis said...

Greg, I think we will still see simple carbohydrates extracted from whatever we grow and molded into cubes and spheres of kid food for quite a while. If raw carrots taste more like wood pulp, people will be less inclined to eat them.

(By the way, has anybody else noticed that the beautiful giant strawberries in the stores these days don't actually taste like strawberries? Or is it just me?)

The idea that the process gets cheaper because of carbon fertilization appears false though. Our machines, like the koala, will have to work harder.

Steve Bloom said...

Watch out, Moe and Eli, those durians will throw your back right out!

Michael, I think red does not equal ripe the way it once did. Try letting them ripen completely (outside the refrigerator).

skanky said...

"(By the way, has anybody else noticed that the beautiful giant strawberries in the stores these days don't actually taste like strawberries? Or is it just me?)"

Half a dozen wild strawberry plants will, in a year or two, produce quite a ground cover. The very small fruit tastes amazing.

Very little nurture required, though in Texas you may need to water them at times, I guess.

They do also grow well in containers, though, which will help the water retention.

guthrie said...

Michael - large tasteless strawberries have been very common here in the UK for at least 12-14 years. This is in part due to the dominance of the supermarkets, who ship them in from Spain out of season, and also because of the way modern agriculture works and the demands of the supermarkets they want something that looks good and survives transport well and has a good shelf life.
Actual taste is rather more unusual to find. All too frequently 90% of strawberries available are Elsanta, which don't have much of a flavour, although better than the steroid strawberries.
However due to the shelf life things (And perhaps their high water content), if you let the strawberries ripen outside the refrigerator, you have about 3 minutes in which they are in good condition before they get fuzzy or mushy.

ON the CO2 fertilisation meme, I recall that Freeman Dyson did some back of the envelope calcuations in one of his books 15 or more years ago which showed that some percentage of extra CO2 was going into the biosphere. Hence his later obsession with carbon eating trees.

dhogaza said...

"This is in part due to the dominance of the supermarkets, who ship them in from Spain out of season"

They grow them in the south, in giant hothouses.

You can get good strawberries in spain at the right time of year, though ... but I bet the domestic market slurps them all up.

Also good strawberries simply don't ship well, they're too soft, bruise easily, etc.

Come visit Oregon in June, we have fantastic strawberries. They're delicate, though, barely survive shipping from 20 miles outside portland through the supermarket distribution warehouse into the store.

But bursting with flavor.

Oale said...

For those wishing to delve in the research http://www.skepticalscience.com/co2-is-plant-food-too-simple.html compiles some recent studies made on Rubisco (enzyme on plants that fixes CO2 to living matter) and more. There aren't too many protein complexes involved in carbon fixation (6-10 (depending on how you count), consisting of numerous sub units), but all of them have required quite a lot of research to get characterized, Rubisco being the focus of many studies.

David B. Benson said...

Find recipes for kudzu.

adelady said...


Probably more likely to produce something vaguely food-like than ANYthing you could do with, to, about or around eucalyptus.

But then that's probably true of 98% of the plant world.

Marion Delgado said...

One thing pot cultivation did for some was introduce them to Liebig's law of the minimum. Hopefully, the new move to grow your own food will do likewise. I always read plants would be spindlier and more fibrous, often too limited by other constraints to grow more with even unlimited CO2, and that weeds would benefit more from CO2 than cultivated plants on average.

I do "retweet" some things michael writes, but i'll try to link to the blog more, too.

Jim Bouldin said...

No. This kind of thing just give ammo to the deniers--and rightly so. The linked article has no cites or specifics about the studies referred to and then concludes that Koalas may go extinct?!?. That's pathetic.

Plant response to CO2 increase--and many changes in inputs for that matter--varies widely. CO2 increase has positive or negative effects depending on other growth factors. For example, when either soil moisture levels or high temperatures are not limiting, CO2 increases are generally beneficial, because CO2 conductance is increased, thereby reducing photorespiration rates (at least in the largest group of plants on the planet, which have a certain photosynthetic system, called C3). At lower soil moistures, when combined with relatively high temperatures, you can start running into problems with the carbon balance, and with leaf temperatures, due to reduced conductance and reduced evaporative heat loss.

CO2 fertilizaton in the wild *may be* altering the mass of leaves that have to be ingested to obtain a defined caloric or nutrient amount, which *may* in turn limit their reproductive rate, which *may* affect their populations in some areas. Just leave it there.

Michael Tobis said...

Jim, a fair point, I should have digged deeper for the original study. But I doubt Camille would have talked about it publicly if there weren't a strong and legitimate study behind it.

Jim Bouldin said...
This comment has been removed by the author.
Jim Bouldin said...

Michael, yes I agree regarding Camille.

Jim Bouldin said...

And sorry for using unexplained jargon. Stomatal conductance is the rate of gas flow through the leaf stomates (pores). In most species these are adjustable. As total pore area drops (i.e. stomates narrowing in response to water stress), conductance drops more rapidly for H2O vapor than for CO2. This is the physiological basis for why CO2 fertilization promotes water use efficiency--the plant is losing less water for a given CO2 gain from the atmosphere. This gain is partially offset however, by the resulting reduced evaporative cooling. All other factors equal, this will increase C loss via increased photorespiration. Therefore, increased [CO2] has two counter-acting effects on photorespiration under water stress.