When it comes to climate change and agriculture, the thinking generally goes as following: Carbon dioxide is plant food, thus except for its effects on the greenhouse effect, its effect on food production will be positive. I don’t believe in this idea, for reasons I explained here. There are too many variables that are generally left out of the equation. One example I explored in the previous essay looked at the interaction between soil nitrogen and atmospheric carbon dioxide concentrations and their combined effect on toxic alkaloid production by a fungal endosymbiont of ryegrass. What was found was that production of these toxins drastically increased under conditions of high soil nitrogen and higher carbon dioxide concentrations, but not if either factor was missing. This would lead to reduced milk production and sickness in cattle, as well as potentially any humans exposed to their milk.

Another example of a known unknown I’ve looked at is the effect that elevated carbon dioxide concentrations has on food spoilage organisms. Not much has been written about this subject, but today I stumbled upon a study by Medina et al, that looked at the effect of the interaction between temperature, carbon dioxide and moisture levels on Aspergillus flavus growth and its degree of Mycotoxin production. The effect seen is very worrisome.

What was found is that although elevated CO2 (650 ppm) generally has no significant effect on Mycotoxin production at 34 degree celsius, at 37 degree Celsius, which is A. Flavus ideal temperature, elevated CO2 was found to increase Aflatoxin B1 production by anywhere between 15 and 80 times, depending on moisture content. There was generally no significant difference between 650 and 1000 ppm, which could indicate that the saturation point lies somewhere beneath 650 ppm. Most estimates have us reach 650 ppm somewhere between 2050 and 2100, so this is a problem we could expect to start running into quite rapidly.

What’s important here is to realize how insidious this problem is. Sea level rise and desertification are problems we can visualize, but they’re also problems that can be addressed by migration. This problem is significant because it represents an example where adaptation is going to prove itself to be a very difficult task.

Is A. Flavus alone in its response? Probably not. A long list of fungal plant pathogens that affect growing plants, as opposed to stored food, have been found to perform better under conditions of atmospheric CO2 enrichment. The effect of atmospheric CO2 concentrations on food storage pathogens has so far been poorly studied.

We tend to think of the efficiency of agriculture as self-evident, but the processes it involves are very dependent on the conditions of climatic stability that are known to us as the Holocene. Factors that seem constant and self-evident to us (ie the process of storing food) can be significantly and irrevocably affected within a period of just a few decades.