An Aridamerican model for agriculture in a hotter, water scarce world
The article is the work of some researchers who examined ethnobotanical and historical sources, interviewed native people, and did ecological surveys in “Aridamerica”
Primarily they drew from the current and historical practices of the Comcaac (Seri people), O'odham, and Pima Bajo peoples. Here are a few excerpts from the article I really liked!
Agricultural visionaries from Argentina, Australia, North America, and elsewhere have been calling for “new roots for agriculture” for more than 40 years (Felger, 1975; Jackson, 1980). Their visions favor high biodiversity-low input agroecosystems, with greater emphasis on perennial polycultures. To quote pioneering desert botanist Richard Felger, to whom this article is dedicated, we must “fit the crops to the environment rather than remaking the environment to fit the crops.” Yet, to date few agronomists have given sufficient attention to effective means to reduce heat or moisture stress in crops and livestock, or in the humans who struggle to manage them (Nabhan, 2013).
The majority of widespread crops (e.g., rice, wheat, soybean) are C3 plants with low water-use efficiency and reduced photosynthetic efficiency under high temperatures. C4 crops (e.g., corn, sorghum, sugarcane) have higher heat tolerance but usually require reliable irrigation in arid and semi-arid land settings. As temperatures increase, so do evapotranspiration and water input required to maintain crop yields. Thus, even drought- and heat-tolerant varieties of conventional C3 and C4 crops may be unable to weather—let alone mitigate—the stressful agronomic conditions predicted for arid zones over the coming century. In contrast, wild desert plants have evolved multiple strategies to cope with heat and drought (Gibson, 1996). Desert plants with the crassulacean acid metabolism (CAM) pathway uptake CO2 nocturnally when temperatures are cooler, thereby optimizing water-use efficiency (Nobel, 2010).
I really like the points they make here about C4 plants! Corn and sorghum are often listed as being more suitable for arid climates because of their improved temperature tolerance and water use efficiency compared to (for example) wheat or soybean. That said...both were originally tropical plants iirc, and while there are certainly drought-tolerant cultivars of both, they still use a *lot* of water in very hot and dry regions, and those well adapted cultivars aren’t the most commonly grown.
After gathering a list of plants commonly used as crops by the native people of these areas "For each species, we determined the photosynthetic pathway (C3, C4, CAM) and categorized water-acquisition strategy as extensive exploiter (e.g., Prosopis/mesquite), intensive exploiter (e.g., Salvia columbariae/chia, Phaseolus acutifolius/wild tepary bean), or water storer (e.g., Agave/agave, Opuntia/prickly pear)”
It’s really interesting to think abt those different drought strategies! For reference, extensive exploiters tend to have very wide+deep root systems that collect water from an extensive area. Intensive exploiters tend to be found near temporary water courses that only hold water temporarily/for part of the year. This could mean washes/dry streambeds that flood in a storm, or rivers that dry up outside of the monsoon season. I know tepary beans typically grow quickly (often quoted as taking only 60 days from growth to seed set!) when water is available, then die and weather the hottest and driest season as dormant seeds. Water storer is pretty self-explanatory--agave and prickly pear are succulents that can store a tremendous amount of water in their tissues, saving it to tide them over until the next precipitation event.
Ultimately, the article graded a variety of plant genera on their agroecological suitability (how well they grow in an arid environment), any potential medicinal uses, their community/social value (cultural importance, providing shade in communal areas, etc.), and their agronomical suitability (can it be grown at scale, is there a market for it, etc.) I won’t bother to list them here--you can go see the whole chart in the linked article--but it’s a very interesting list!
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