Will there be Chocolate?
We hear much about the fortunes of corn, wheat and rice, and their various insect competitors for our crop. But what about something even more important for civilization–the cacao tree, source of cocoa and chocolate. In twenty years, will cocoa be rare?
Cocoa production involves one of the most complex fermentations of any food. First the pulp surrounding the beans must be fermented by yeast, generating alcohol; then lactic acid bacteria convert the alcohol to lactate, and acetic acid bacteria oxidize to CO2. And hundreds of other bacteria participate to an extent more or less understood. No laboratory or factory can reproduce the process exactly; it happens beneath a mound of leaves in the rainforest, where indigenous workers turn the pulp, aerate and dry it, ultimately shipping to Western candy makers.
And the genetically inbred cacao plant is a terribly finicky tree, requiring “helper trees,” and subject to an inordinate number of pests with names like witch’s broom and frosty pod rot. Furthermore, the crops worldwide are losing out to drought, deforestation, and global warming.
What’s to be done? Even the Gates Foundation has partnered with Hershey, Kraft and Starbucks to fund the Cocoa Livelihoods Program to sustain the productivity of cacao farmers in West and Central African countries.
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Ultraphyte 
But Cacao is American. It went to Europe and Africa from Mexico and lands further south. How is it doing there?
Cacao does well in South America, but still is vulnerable to disease. The Brazilian crop is severely hit by witch’s broom fungus.
I wonder if the real problem is the same issue that faces rubber and potatoes, that we’ve taken a few genotypes from a fairly diverse wild population (and possibly even cultivated population), and created highly inbred commercial lines from them. If so, part of the answer is (of course) finding resistant wild individuals and getting their resistance genes into the commercial lineages. Wade Davis’ One River has a poignant account of how such an effort to create a resistant rubber tree nursery back around World War 2 was trashed by some truly idiotic bureaucratic bungling.
I’m not too concerned about cacao’s reliance on companion trees. AFAIK, wild cacao is an understory tree, so having other species around it to provide the necessary shade isn’t a weakness, simply part of its basic ecology. Similarly, polyculture and agroforestry seems to be one of the best solutions for farming in the tropics, so I suspect that may be one way for cacao to thrive.
In any case, if we get worst-case global warming, Ohio Valley cacao will be the wave of the future…
Yes, I’m sure the cacao trees are inbred; after all, they must all be descended from a few trees that were transported elsewhere.
The dependence upon other tree species is more complicated, though poorly understood. It is more than shade. It may be that they depend upon mycorrhizae connecting them to the other trees:
Click to access Herre2007.pdf
Oy. I did a bit of work on arbuscular mycorrhizae. While I won’t dispute that a) they’re incredibly cool, and b) they can have the direct and indirect effects as listed in that nice article (and thanks for posting it). Still, I’m not aware of any good evidence that they act to transfer nutrients among plants. It’s possible, but the one distinct test I know of was negative. There’s somewhat more evidence for ectomycorrhizae transferring nutrients among plants.
There’s also the possibility of a subsidy effect. Say you have plants Phil and Phyllis, and AM Fungus Art, and fungus Art grows on both Phil and Phyllis’ roots. Let’s also say that Phil is tiny, while Phyllis is huge. Art’s getting all his carbs from Phil and Phyllis, but he’s getting a greater share of carbs from Phyllis, simply due to the size of Phyllis’ root system. This means that Art’s able to get phosphorus out of a relatively large volume of soil, and pass that phosphorus onto both Phil and Phyllis. Phil may be getting a phosphorus subsidy due to Phyllis being the primary carb giver. Demonstrating this is, as they say, non-trivial.
The thing to realize about AMF is that their hyphae have fairly small diameters (unlike some ectomycorrhizae), and they only grow up to 10 cm away from a host root. Most of them only grow a few centimeters away, and make the roots look kind of cottony. They work not because they grow far away from roots, but because they are so much smaller than roots that they can readily penetrate into soil spaces that root hairs cannot forage in.
While it’s certainly possible to string two plants together with one AM fungus, the roots have to be close to touching. That’s ultimately the problem with saying that the cacao benefit from nutrient transfers from the trees around them. Mechanistically, it’s hard to prove.
I don’t buy African chocolate unless it is fair trade because of the child slavery.