Yes, yes, we hear it all the time: More CO2 is good because plants love CO2

That is a rather dumb thing to say for a number of reasons; nature is not simple. You don’t change one variable and expect other variables to respond as though we were turning a garden hose up or down. For example, while plant growth might be enhanced with more CO2 in the atmosphere, there is no reason to think this would be linear, or similar across all plants. You have to dance with the one who brung ya. The plants we have are the plants that have been under Darwinian selection optimizing growth and maintenance physiology for gazillions of plant generations. Changing a fundamental variable may have little effect (and in fact, CO2 increase only enhances growth somewhat, and for only some plants) and may even have negative effects.

A new paper out in Ecology looks at the nutritional value of plants in a Ugandan rainforest and finds that the nutritional value of the leaves eaten by some Colobine monkeys there has declined, because fibre has increased at the expense of usable protein. From the abstract:

Global change is affecting plant and animal populations and many of the changes are likely subtle and difficult to detect. Based on greenhouse experiments, changes in temperature and rainfall, along with elevated CO2, are expected to impact the nutritional quality of leaves. Here, we show a decline in the quality of tree leaves 15 and 30 years after two previous studies in an undisturbed area of tropical forest in Kibale National Park, Uganda. After 30 years in a sample of multiple individuals of ten tree species, the mature leaves of all but one species increased in fiber concentrations, with a mean increase of 10%; tagged individuals of one species increased 13% in fiber. After 15 years, in eight tree species the fiber of young leaves increased 15%, and protein decreased 6%. Like many folivores, Kibale colobus monkeys select leaves with a high protein-to-fiber ratio, so for these folivores declining leaf quality could have a major impact. Comparisons among African and Asian forests show a strong correlation between colobine biomass and the protein-to-fiber ratio of the mature leaves from common tree species. Although this model, predicts a 31% decline in monkey abundance for Kibale, we have not yet seen these declines.

Jessica M. Rothman, Colin A. Chapman, Thomas T. Struhsaker, David Raubenheimer, Dennis Twinomugisha, and Peter G. Waterman, 2014. Long term declines in nutritional quality of tropical leaves. Ecology

Comments

  1. #1 John Mashey
    September 22, 2014

    Many gardners know adding CO2 to sealed greenhouses works well … given the right sun, water and nutrients, i.e., balanced to the right mix.

    Farm kids learn Liebig’s Law of the MInimum pretty young.

    No matter how high the CO2 goes, teh Shara is not going to be Iowa.

  2. #2 Tim
    September 24, 2014

    Well, I’ve always been one of those ‘CO2 is plantfood’ guys, myself. I think I can see that protein may become more concentrated in slower growning leaves.

    But, without looking at the paper (when I get the cookie page, it matters not what I do with cookies or scripts — no page),

    the fiber of young leaves increased 15%, and protein decreased 6%

    So is that saying that although protien concentration went down the total protein still went up (bigger leaves)? — Probably more of them to.

    Regardless, I feel it insignificant when considering Monstanto, factory farming, and monoculture crops — Agenda 21 implementation to combat CO2 will destroy individual and small scale, distributed agriculture with its’ attendant corruption and destruction of biodiversity. <– This is nothing more than controlling all life and it is happening right now

    Now, it is being advocated to replace healthy living biomes with *green desert*, pine forests, for higher ‘sequestration’ of CO2. This sequestration is ‘higher’ because the life is less. A healthy biosphere requires a healthy overturning of CO2.

    http://treesearch.fs.fed.us/pubs/2420

    And *they* hate kudzu also for the same reasons — it produces healthy, rich soils and biodiversity whereas pine kills it.

    http://arstechnica.com/science/2014/07/invasive-kudzu-drives-carbon-out-of-the-soil-into-the-atmosphere/

    I *think* The proper way to sequester carbon into the soil, support a diverse biomass, and *grow* more rich soil would be to replicate/teach terra preta:

    http://en.wikipedia.org/wiki/Terra_preta#Organic_matter_and_nutrients

    As that doesn’t fit the agenda, it will surely be outlawed in the home garden or otherwise treated like the weight of dirt and plant is the weight of plant when following sentencing guidelines of other brands of prohibition.

  3. #3 Tim
    September 24, 2014

    After 30 years in a sample of multiple individuals of ten tree species, the mature leaves of all but one species increased in fiber concentrations, with a mean increase of 10%; tagged individuals of one species increased 13% in fiber. After 15 years, in eight tree species the fiber of young leaves increased 15%, and protein decreased 6%

    “tagged individuals”

    which species didn’t ‘decline’? Did it enhance?

    “concentrations” is left hanging without disambiguatizing between concentration and ‘total content’ in that last sentence….

    It’s only the synopsis but, still, that is a bit of ‘wiggle room’ — I’d be interested in the concentrations/content of the slightly older ‘adolescent leaves’…