The productivity of that biologically barren monoculture of GM corn is an illusion, dependent on manufactured inputs of fertilizer, chemicals, and unnatural seeds for survival. A break in the supply chain or a season on the rain-stingy side cripples the crop, which must mature all at once or be a loss for the year. Even then, the proprietary seeds are illegal to replant and are of diminished eating value, victims of the genetic push for high volume rather than food quality.
By contrast, a milpa's crops provide different kinds of nutrients that complement one another for great benefit, just as they help each other grow in the field. Corn, the trellis, elevates bean, the nitrogen-maker, and expands its exposure to the sun. Both crops benefit from the dense and weed-suppressing foliage of squash, the green wanderer. Besides three kinds of human food borne over a period of months, the synergetic trio provides habitat for amphibians, birds, and insects. The broad leaves form a canopy to protect soil microbial life from being cooked and to cushion the impact of rain that could compact soil structure. Healthy soil is the foundation and the result of this sustaining system, which, each season, yields seeds one year better adapted to the place where they grow.
Much like the balanced ecosystem of virgin prairie, well-balanced plant combinations help protect against typical stressors:
Dry times. The water-holding capacity of soil that is rich in organic matter—with high biological activity and balanced fertility—sustains crop yields even when rainfall is short. Long-term soil building deepens its aerobically active layer and improves the soil's physical structure, which then favors the development of roots. More roots, pushing deeper, with more fine root hairs overall, vastly increase each plant's ability to absorb moisture and nutrients.
Pests. The Rodale Institute's experience in the drylands of Senegal illustrates how a wisely developed crop mixture works as a powerful polyculture. Mixing plots of corn, peanuts, and millet (a grain) with tall hibiscus-family crops builds in safeguards: It reduces plant stress through shading and wind-buffering, provides more flowering periods to feed beneficial insects, and introduces new plants to serve as nonhost species to thwart the spread of insects. Each crop contributes something to stabilize the whole system against environmental shocks and flux.
High heat. Eliminating crop "holes"—spaces between crops where the leaf canopy is incomplete—shelters soil from the sun (and keeps weed seeds from germinating). Buckwheat quickly covers soil between early and late crops, while cucumbers grown between rows of sunflowers keep their shallow roots shaded. By creating a moist microclimate at the soil level, the leafy cover benefits all roots and allows them to better sustain their plants. Remember the milpa.
Climatic extremes. Hotter than ever one year, wetter the next, drier and colder the next: From Bangladesh to Kenya to Texas, extreme years are becoming more routine. Native and naturalized species are opportunistic in being able to exploit available resources in hard times. They may yield less than imported crops when conditions are ideal, but they prove their worth in years of weather extremes—the ones that are becoming more common.
Be on the alert for new plant combinations that are able to thrive through the extremes. Look for pairings that result in "overyielding," where two or more crops grown together each produce at a higher level than if they were planted alone. Add a flour corn to your squash patch, geometrically interplant head lettuce and onions, or create wide beds of okra or popcorn with edamame soybeans.
Resilience is also the human ability to recover quickly from disruptive change or misfortune without being overwhelmed or acting in dysfunctional or harmful ways. Learn from your garden: Diversify, put down roots, stay centered in crazy times, and associate with those who fill in your places of need. Be resilient.
Greg Bowman is the former Communications Manager at the Rodale Institute