Where Does Nature’s Wisdom Lie?

IMG_2378R. Ford Denison in Berfrois:

Consider wild rice, shown above growing near the headwaters of the Mississippi River. Natural selection has been improving this species, by evolution’s criteria, for millions of years. Better-adapted plants (those best at extracting nutrients from flooded soils, defending themselves against pests and pathogens, and producing seeds in warm and cold years, in deep or shallow water), had more surviving offspring. Their descendants inherited those adaptations. So plant breeders developing new rice varieties (especially for farmers who can’t afford fertilizer or control water depths) might learn something useful from research on how wild rice faces similar challenges.

What about nature’s “lies”? Notice that wild rice grows naturally almost as a monoculture, not mixed with other plant species. Tropical forests, on the other hand, have much greater species diversity. Can we conclude that aquatic plants, like rice or taro, should be grown as monocultures, while tree crops should be grown as diverse mixtures of species? Or maybe cold climate crops should be grown as monocultures (many northern forests aren’t very diverse either), while tropical crops should be grown as mixtures.

These hypotheses implicitly assume that natural selection, or other natural processes, have improved the overall organization of natural plant communities, not just the individual species that live there. Most evolutionary biologists, however, tell us that natural selection is much better at improving trees than forests. This is especially true when the interests of individuals conflict with those of the community as a whole. A more diverse forest might be less susceptible to disease outbreaks, but that won’t stop individual redwood trees from growing taller and shading out competitors of other species. Similarly, the low diversity of wild rice stands doesn’t prove that more diverse plant communities wouldn’t be more productive, more efficient in the use of scarce resources, or more sustainable over decades.

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