Biomimicry

by Janine M Benyus

  As the first step toward an agriculture that organizes itself into arrangements of strength, Piper’s job was to ascertain just what it was about the prairie’s structure that made it so tough. Is there a rule of thumb about which categories of plants consistently show up on a prairie roster, and what ratios they are in? Does it matter where they grow in relation to one another? In search of answers, Piper read everything he could about prairie ecology, and then spent seven glorious summers up to his eyebrows in wild pastures. He and his interns actually took scissors and clipped and bagged all the vegetation in certain plots. They identified each and every plant, separated them out into piles, and then dried and weighed them to find out what grew there. Through wet years and dry years, in rich soil and poor, Piper found that prairies do have a pattern that repeats itself, an order in the seeming chaos.

  “The first thing that strikes us,” says Piper, “is that ninety-nine point nine percent of the plants are perennials. They cover the ground throughout the year, holding the soil against wind and breaking the force of raindrops. Hard rain hits this canopy of plants and it either runs gently down the stems or it turns into a mist. By contrast, when rain hits row crops, it strikes exposed soil, packs it, then runs off, taking precious topsoil with it.” Researchers have actually measured the difference; in identical downpours, they found that you get eight times as much runoff from a wheat field as from a prairie.

  “Prairies just soak up a big rain,” says Piper. “I can come out here hours later, and The Wauhob still squishes when I walk on it.”

  Besides being great sponges, perennials are also self-fertilizing and self-weeding. Thirty percent of their roots die and decay each year, adding organic matter to the soil. The remaining two thirds of the roots overwinter, allowing perennials to pop open their umbrella of vegetation first thing in the spring, long before weeds can struggle up from seed. As we walk through a particularly dense patch of prairie, Piper crows, “See? You wouldn’t have a chance in there if you were a weed.

  “The second thing that strikes us about the prairie is its diversity,” Piper says. “We have two hundred and thirty-odd species right here on this knob—not just one species of warm-season grass, but forty species. Not just one nitrogen-fixing legume, but twenty or thirty. That means that there will always be some species or some variety of a species that can do well in our highly variable Great Plains climate. I’ve been out here in dry years when the grasses barely reach your knee and there’s yucca everywhere. Other years, after plenty of rain, you and I could stand three feet apart and not be able to see each other through the big bluestem. The species composition remains the same, but different species excel in different years.”

  Diversity is also the cheapest and best form of pest control. “Many pests tend to specialize on one host plant species, so when there’s a diverse mix, pests have a harder time finding their target plant. Even if they manage to touch down somewhere in the field, the attack troops don’t get very far. Disease spores may blow onto the wrong plant, or insect young may crawl into the wrong bud. With a diverse offering, attacks die down before they become epidemics.”

  The third signature of the prairie is its four classic plant types: warm-season grasses, cool-season grasses, legumes, and composites. Cool-season grasses come up early, set seed, and then bow out of the way, allowing warm-season grasses such as big bluestem to rule the rest of the season. Legumes such as cat’s-claw, sensitive brier, and leadplant fix their own nitrogen, fertilizing the prairie with their bodies. Composites, such as goldenrod, asters, and compass plants, can flower anytime throughout the season. Although these four “suits” may vary in proportion from place to place, Piper found them in every prairie he waded through.

  “Learning the secrets of the prairie gave us a goal to shoot for as we sifted through the countless combinations of plants that would qualify as prairie mimics in our agriculture. We knew we needed perennial grains grown in a polyculture, with the four suits of the prairie represented. The only question was how many different species in each group will we have to plant? Since it’s impractical to have an agriculture with two hundred species, how much diversity will we need to get functional stability? Our intuition told us that we would probably have to plant many more species than we need and let the assemblage shake down over a few years to the handful that would provide human food. Just about then, ‘community assembly’ studies started to show up in the literature, and they suggested that you could get persistent communities containing as few as eight species. That was encouraging to us.”

  Breeding eight perennial crop species from scratch looks more feasible than breeding two hundred, but it’s still a daunting challenge. Today, most of the food eaten around the world comes from only about twenty species, and none of them are perennials! Some began as perennials, but over the ten-thousand-year odyssey of plant breeding, we systematically removed their hardy perennial traits, marching right by the sweet spot between wild and tame, and domesticating them until they were annual by nature.

  A story is told about the moment Wes Jackson realized the full extent of this unhappy extreme in agriculture. Shortly after starting his school, Jackson took his students on a field trip to the eight-thousand-acre Konsa Prairie near Manhattan, Kansas. One of them asked the innocent question, “Are there any perennial grains?,” and it made Jackson think. When he got back, he drew up a list of all the crops he could think of, separating them into either annual or perennial, herbaceous or woody, vegetative or seed/fruit yielding. To his surprise, there were crops that fit into almost all the categories, but there was a glaring blank in the space for HERBACEOUS, SEED-YIELDING PERENNIAL. It was a revelation in black-and-white.

  PERENNIAL OPTIMISTS

  Jackson and his staff started tearing apart the literature—surely someone must have done some plant breeding on perennial grains. They were disturbed to find that no one, save some folks looking at animal forage, had studied seed-yielding perennial grasses or legumes or composites. The reason?

  “It was a nonstarter for career-oriented scientists,” says Jackson. “The common wisdom was that perennials, which spend most of their energy belowground, could never be made to produce copious seeds [the part that humans eat]. If they were to yield more seeds, the thinking went, there would be a trade-off belowground, and they’d lose their ability to overwinter.”

  Jackson, who’d made a career of bucking conventional thought, said not so fast. The first question The Land Institute assigned itself was the one everyone else had skipped:

  Can a perennial produce as much seed as an annual crop?

  After two more years of library safaris and actual planting experience, The Land Institute staff was convinced that perennials could be bred to yield plentiful seeds without losing their perennial traits. Illinois bundleflower and wild senna, for example, were two wild perennials that, with absolutely no breeding, already approached the benchmark yield (the floor range) for wheat in Kansas: eight hundred pounds per acre. Considering that the wild relatives of some of our crops have undergone four-, five-, even twentyfold seed-yield increases at the hands of talented breeders, the chances of upping yields for these new crops were good.

  The trick this time around would be to increase seed yield without stripping the plant of its wild hardiness. Curious to see what artificially increased seed yield would do to plant vigor, Jackson’s daughter, Laura Jackson, a researcher at the University of Northern Iowa, conducted an experiment that showed that a plant need not sacrifice photosynthate—the ability to feed itself—when it puts out lots of seeds. In short, the trade-offs were not as strict as everyone imagined, and it seemed that the chimera The Land Institute wanted to create was well within the realm of the possible.

  In 1978, the staff embarked on the painstaking process of breeding crops for the domestic prairie. They would have to possess not only hardiness but also “crop character”—qualities like good taste and ease of threshing. Since the breeding of most of the crops we eat today was fa
irly well wrapped up by Abraham’s time, crop domestication of this sort was a brave new venture. The precedent for this work completely disappears when you consider that Jackson and crew were shooting for crops that were dependable, but not dependent on us.

  There were two ways they could wind up with a perennial grain—one, they could start with a wild perennial and boost its seed yield and crop character, or two, they could start with an annual that already had good crop character and cross it with a perennial wild relative to refresh its memory about how to survive the winter. Now all they needed were candidates.

  Going on catalog descriptions of native perennials in each of the groups, they ordered nearly five thousand different types of seed from governmental seed collections and planted them in the undulating fields by the Smoky Hill River. Those that survived well in Kansas weather and had a whiff of a hope for high seed yield became candidates in their breeding program. They planted the seeds and waited anxiously, as farmers do, to see how the plants matured. Besides seed yield, they were also looking for agronomic characteristics important to a farmer: reduced seed shattering (so seed heads don’t break open and spill their grain before harvest), uniform time of maturity, ease of threshing, and large seed size.

  The four most promising candidates for perennial domestication turned out to be eastern gamagrass (Tripsacum dactyloides), a sprawling warm-season grass that is a relative of corn; Illinois bundleflower (Desmanthus ittinoensis), a legume that grows tall and produces a baby rattle of seed pods; mammoth wildrye (Leymus racemosus), a stout cool-season relative of wheat that the Mongols used to feast on when drought claimed their annuals; and Maximilian sunflower (Helianthus maximilianii), a composite that yields oil-rich seeds, which could be pressed to create vegetable oil diesel fuel for tractors. The second approach—starting with an annual and hybridizing it with a perennial—led to the mix of milo grain sorghum, which is already used as a crop, and perennial Johnsongrass.

  Now that The Land has its lineup, the breeding has begun in earnest. The very best individuals from each species are grown together in one plot so that they can cross-pollinate. When two promising strains “mate,” the hope is that even more bodacious offspring will follow. The seeds from each trial are planted out (in various kinds of soil to make sure the differences are truly genetic, or inheritable, and not just environmental), and the best individuals are selected to cross-pollinate once again. This process is repeated until the improvements due to crossing show signs of diminishing returns. Only then will the breeders call them good and begin the fine-tuning process to bring out each strain’s best features.

  So far, optimism at The Land is high, which means a slightly deeper nod from the incredibly modest Jon Piper when I ask whether he’s pleased with their progress. He walks me among the monoculture and polyculture plots where the best of the best are showing their stuff. Some collections of eastern gamagrass are bravely resisting various leaf diseases, and certain collections of bundleflower and gamagrass are yielding well despite some drought. The most vigorous crosses between Johnsongrass and grain sorghum are showing both high seed yield and good rhizome production. (Rhizomes are the underground runners that allow plants to store starch for winter, and thereby survive.)

  In terms of seed yield, there are already some superstars. Even though its food value has yet to be explored, says Piper, Illinois bundleflower is yielding seed quantities that approximate the typical yield of nonirrigated soybeans in Kansas. For eastern gamagrass, which can be ground into a cornmeal and baked into a palatable bread, the potential to improve seed yields is great, thanks to a variety that was discovered along a Kansas roadside. The collector noticed that instead of the normal flower stalk, which is composed of about one inch of female flowers topped by four inches of male flowers, this sport had all female parts (which turn into seeds) except at the very tip. If all yielded, the sport could produce up to four times the normal amount of seeds. As Piper shows me one of the stalks, I notice that the female organs are green. “Exactly,” he says. “That means they can photosynthesize and pay their own bills, meaning the plant won’t necessarily have to trade off fewer roots in order to support more seeds. That’s what we’ll be trying to show.”

  By taking on this perennial-grain breeding challenge, folks at The Land Institute were already mucking in that part of the map that warned “serpents lie here.” While they were at it, they thought they’d try for another first by choosing most of their candidates from native stock. (The only plant in their lineup that isn’t native is mammoth wildrye.) Though native stock seems an obvious choice, it hasn’t been to other breeders. Most of our crops are exotics, brought over in our traveling bundles from Mexico and Europe. The only native plants that we have ever domesticated in this country are sunflowers, cranberries, blueberries, pecans, Concord grapes, and Jerusalem artichokes. The Land Institute is trying to lengthen this short list, knowing that natives are tuned through evolution to sing in harmony with the melody of local conditions.

  While coaxing agronomic manners from these plants will be a Pygmalion task, growing them in monocultures at least gives breeders a chance to compare apples with apples. Unfortunately, says Jackson, we can’t stay with monocultures. The real Holy Grail is to grow them in polyculture—mixed species plots—since, as nature has shown us, only poly cultures are able to pay their own bills.

  POLYCULTURE SHOCK

  Polyculture is not music to a breeder’s ears. When you are working in a polyculture, you take all the difficulties that you encounter in monoculture breeding and multiply them. You are not only selecting for high yields, large seed size, uniform maturation time, easily threshed seeds, low shattering, winter hardiness, disease and pest resistance, and climate tolerance, but also for compatibility—a plant’s ability to perform well or even exceed performance when grown next to other plants.

  The Land Institute staff was essentially faced with designing an agricultural dinner party, deciding who should be seated next to whom to maximize the beneficial interactions and minimize the detrimental ones. Nature arranges these kinds of matchups all the time through the slow culling of natural selection. Could The Land somehow mimic and speed up this process?

  “The traditional scientific method offered one way to go about it,” says Piper, “and we worked this way for a while—planting out seedlings in mixed plots, purposefully putting certain species next to others so we could investigate their interactions.” The problem was that the number of possible combinations is astronomical, and not even a Mendelian monk’s life would be long enough to try them all. Just as Piper and his colleagues started questioning this reductionist approach, they began to read about recent developments in the field of community assembly.

  James Drake and Stuart Pimm of the University of Tennessee study what it takes to arrive at an assembly of species that remain in equilibrium, a condition farmers would obvously want for their domestic prairie. Unlike The Land staff, they do their experiments with ecosystems in a computer (artificial life) and with aquatic organisms in glass tanks (real life). They begin by adding species in various combinations and then letting them work out who will survive and in what ratio. Eventually, without intervention, the community shakes down into something that is both complex and persistent—order for free. “But we don’t get order immediately,” says Pimm. “We get it after a long period of adding species to communities and watching them come in, displace other species, and go extinct in their turn.” In other words, having a history is what makes a community last.

  In his famous “Humpty Dumpty” hypothesis, Pimm maintains that once you destroy a finished product of community assembly, such as a prairie, you can’t just plant those same species and expect to put it back together again. There’s no such thing as an instant prairie. A prairie restorationist must give the prairie a successional history, that is, actually grow the prairie over a trajectory of years. Some plants will blow in and others will drop out, but as those facilitating species change the soil and the fauna
and flora around them, they make it possible for the final assembly to be there. They warm up the crowd for the real act.

  “The question for us mortal scientists,” says the understated Piper, “and for farmers who will someday grow diverse perennial grains, is how to get that order quickly. We’re not in the business of creating prairies over a thousand years. What we want to do is build complex, persistent systems that shake down within a very few years.”

  Nor do they have a thousand years to do the research. What Piper and company have decided to try, in addition to their more reductionist experiments, is a “shakedown” like those that occur in Pimm’s and Drake’s experiments. First, they laid out sixteen plots (sixteen meters by sixteen meters), then randomly broadcast seeds that represented the prairie’s four “suits”: warm-season grasses, cool-season grasses, legumes, and composites. In some plots they sowed only four species, in others eight, twelve, and sixteen. There are four replicates of each treatment. Half of the plots are being left alone to develop as they will, and the other half are called “replacement” plots. After two years, any species in the replacement plots that have dropped out or failed to germinate will be replaced. “We want to give our target species every opportunity to join the community,” says Piper. “It may be that mammoth wildrye can’t establish itself in the first year or the second year, but it can in the third.”

  They’ll keep track of which species comes on line when, and which of the plots leads to their desired community first. All the while they will be tracking changes in the communities and looking for rules and patterns about how stable communities assemble. Within a few growing seasons, they want their target perennial grains to be well represented, and to yield abundantly year after year without weeding or seeding. If a few other noncrop species are present in the mix, so be it. “If a plant is consistently present, it probably plays a role in maintaining stability,” says Piper. Eventually, the “recipe” or trajectory the researchers discover will be something they can offer to farmers.