THE CHILDREN’S SONG URGES HER TO FLY AWAY HOME, but the ladybug—or ladybeetle, as she’s properly called—is anything but a homebody. After feasting all summer on soybean aphids and other crop pests, the beetles take off from farm fields in search of snug overwintering spots, often winding up in people’s houses. Around Madison, this usually means a journey of five miles or more, says CALS entomology professor Claudio Gratton. But the insects can also fly much farther. In the Southwest, for example, they congregate on mountaintops. “You’ll come upon a bush just dripping with ladybeetles, and you know they probably had to travel 30 miles to get there,” says Tim Meehan, a research scientist working with Gratton who earned his doctorate in
Those wandering ways got Gratton and Meehan wondering a few years back if the beetles’ lives were touched not just by the soybean fields where they fed, but by the wider world as well. They soon discovered that, indeed, “What the landscape looks like actually makes a big difference,” says Gratton. In experiments across the Midwest, ladybeetles devoured more aphids in fields nestled within a patchwork of woods and grassy pastures than in those surrounded by soybeans and corn as far as a bug’s eye could see.
Although the two still aren’t sure why this is, it led them to ponder another possibility that has big implications for the sustainability of our farmlands. If the chance variation that exists in some farming areas already gives ladybeetles a boost, what if farmlands were purposely designed for diversity? Would the insects dispatch even more aphids? Might they even become tiny tools of sustainability, allowing farmers to spray fewer chemicals?
It takes a lot of imagination to picture such a landscape today, with two-thirds of the Midwest’s cropland blanketed in corn and soybeans. But there is a force that could re-stitch the Corn Belt into a crazy quilt—the push toward ethanol and other types of bioenergy. True, the ethanol blended into gasoline today still comes exclusively from corn kernels. And few “dedicated” bioenergy crops, such as grasses, have been sown so far for making cellulosic ethanol from stalks and stems, or burning in power plants instead of coal.
But bioenergy crops will almost certainly grow widely one day. The goal of the U.S. Department of Energy (DOE) is to replace 30 percent of gasoline and other U.S. transportation fuels with biofuels by 2030. And that, CALS scientists say, offers a chance to reshape our farmlands in an unprecedented way, so they yield not only food and fuel, but also things like ladybeetles and the benefits they provide.
In scientific parlance those benefits are called “ecosystem services”—natural processes we rely on but don’t usually pay for, Meehan says. Pest control by ladybeetles is one service; pollination by native bees, water cleansing, soil formation and even aesthetic beauty are others. Today’s simplified agricultural landscapes excel at producing corn, cotton and other vital commodities in massive amounts, but these may come at the price of water quality, erosion, loss of bird and insect habitat and increased pesticide use, as another study by Meehan and Gratton recently found. The question now is whether switchgrass, willow and other biofuel crops could cut those costs by sowing some plant diversity back into the system.
“The focus now is land use, not just food or fuel or a new crop. How do we use land sustainably?” says Chris Kucharik, a CALS professor of agronomy and environmental studies. “It just so happens that fuel has ignited the debate over sustainable land use right now.”
At the same time, strong forces are working to maintain the status quo. Skyrocketing commodity prices and rising demand for ethanol have led many farmers to put as much land in corn as possible. This year, 92.3 million acres were planted, according to the U.S. Department of Agriculture, four million above last year’s total and the second highest amount since World War II.
Meanwhile, the lack of markets for dedicated biofuel feedstocks, such as switchgrass, has created demand for cornstalks, slash from timber harvests, and other agricultural and forest “waste” as fuel sources for power plants, even though decades of research show these materials are critical to ecosystems—and that their removal could be damaging.
Even the promise Gratton and Meehan see in bioenergy crops could easily be wiped away. Much will depend on which crops are planted and where, as well as how much water, pesticides and fertilizers they need. Growing them might also release more of the greenhouse gas, carbon dioxide (CO2), than the plants pull in, negating what’s considered their premier advantage over fossil fuels.
The uncertainty has generated a flurry of new research in CALS.
“Biofuels are a force that we think is going to change things for the next 100 years,” says Kucharik. “So we want to make sure we get this right.”
Few people likely believed 10 years ago that biofuels could be gotten wrong, so naturally “green” did they seem. Then ethanol made from corn grain came along. Widely hailed at first as plentiful, non-polluting, and a cure-all for peak oil and climate change, it descended almost immediately into a storm of criticism for being, opponents contended, none of these things.
With every two of five rows of U.S.-grown corn destined for ethanol plants today, the cloud still hasn’t lifted, and now cellulosic biofuels are being similarly accused. The difference now is that federal agencies are paying more attention to the potential problems—and paying for research to help prevent them. The DOE, for example, funds the Great Lakes Bioenergy Research Center (GLBRC) based in CALS, whose team of engineers, microbiologists and other technology-focused types also includes scientists like Gratton, Meehan and Kucharik who study sustainability and ecosystem protection.
If this suggests that the health of farmlands is a newfound concern, however, biological systems engineering professor Doug Reinemann assures it is not. Disasters like the Dust Bowl, in which eroded topsoil blew up in vast, black blizzards for nearly a decade, taught the country long ago that soil and water needed protecting even as they were being used to produce food. The environmental regulations and programs that have since been enacted aren’t perfect, but they have taken us a long way from the days when livestock grazed in streambeds and sensitive lands were plowed up at will. Reinemann sees the emphasis now on ecosystem conservation as a natural outgrowth of these earlier efforts.
“It’s really a continuation of traditional soil conservation,” says Reinemann, who leads the GLBRC effort to model the impacts of biofuels crops on landscapes. “But I think we’re also looking at it in a broader sense, particularly with the issue of landscape diversity and the importance of insects, birds and soil microbes—that they’re essential in providing ecosystem services.”
One CALS scientist who was examining these questions long before biofuels became popular is agronomy professor Randy Jackson. A grasslands ecologist, Jackson has spent much of his career studying the environmental and agronomic value of seeding native prairie grasses, such as switchgrass and big bluestem, into pasturelands planted in more traditional forages. When the “biofuels juggernaut” came along, he says, the sustainability questions the GLBRC wanted to ask were right up his alley. He now co-leads its sustainability research group with Michigan State University professor Phil Robertson.
The group’s mantra is the “three Ps.” First, biofuels crops must be productive, Jackson says, because farmers need to make a living. Also favored are perennial plants, whose deep, lasting root systems cut erosion, build soil organic matter and scavenge nutrients, in contrast to corn and soybeans that leave ground bare in winter and must be replanted every spring.
Then there is polyculture, which simply means planting a mixture of species as one crop versus the monocultures we mostly cultivate today. Assortments of plants, the thinking goes, use nutrients more efficiently because individual species take them up at different times and they perform more functions, such as fixing nitrogen or resisting drought, than do single species.
GLBRC scientists are still debating a fourth “P”: placement on the landscape. “We aren’t so starry-eyed as to think that there won’t be monocultures planted in the future,” Jackson says. “So what we’re pushing for is that we maintain diversity between patches, so we have patches of switchgrass and corn and woody crops.”
Due to all this hypothesizing, a section of Arlington, the CALS agricultural research station 20 miles north of Madison, now resembles Jackson’s vision in miniature. Alongside traditional row crops like corn has sprouted a mosaic of switchgrass, shrubs like willow, an Asian grass called miscanthus and mixtures of prairie species. They are all auditioning for roles as tomorrow’s bioenergy crops, and the researchers are scrutinizing them from every angle.
Jackson’s students, for example, are examining nutrient use. “The neat thing about prairie grasses is they resorb nutrients at the end of the season,” Jackson says. After hitting their peak of growth in August, he explains, the plants shut down over two to three months, pulling nutrients and carbohydrates back into their roots for use again in the spring. Measurements by his group show that up to 70 percent of plant nitrogen gets recycled this way, suggesting that prairie species might need less fertilizer as bioenergy crops than does corn. By pulling nutrients from deep soil layers, their roots might also reduce nitrate leaching into groundwater and runoff into lakes and streams.
Bioenergy crops could also be a boon to birds and insects. Wisconsin alone hosts some 500 native bee species, most of which don’t form hives like the social European honeybees do. Instead, they’re solitary creatures, Gratton explains, that crawl inside cavities in trees, holes in the ground or dried stalks of flowers and grasses to lay their eggs. “They have nesting requirements that are very diverse,” he says, “and if all you have is corn and you’re looking for stem-nesters, you’re not going to find a lot of them.” But a lack of bees isn’t what is most troubling, he adds. It’s loss of the service they provide: pollination.
For his part, Kucharik studies one of the most critical services of all in this era of climate change: Locking away carbon in plant tissues and soils to cut CO2 levels in the atmosphere. Many people assume this will happen automatically so long as some kind of bioenergy crop is sucking up the gas, but the situation is actually more complex, Kucharik says. Take corn, for example. “Corn is actually great at converting energy from the sun, water and CO2 into plant biomass,” he says. “But it’s really the net soil storage in the long term that’s important.” Most corn biomass gets removed from the ground every year, he notes. And the rest is often tilled under, releasing additional CO2 as microbes are stimulated to break down organic matter in the soil.
Here again is where prairie species could shine: After all, their massive root systems built the Midwest’s fertile, carbon-rich soils in the first place. Even if they are widely planted as bioenergy crops, however, accumulating carbon will take a very long time—if it happens at all. “That’s really what we’re going toward in my research,” Kucharik says. “Will we store carbon? And if so, how much?”
Despite the caveats, many are still betting that biofuels will ultimately drive farmlands toward greater diversity and ecosystem health. The impact on forests, though, could be very different. In fact, CALS forest ecologist David Mladenoff fears bioenergy is taking them in the opposite direction.
For decades, Mladenoff has studied what keeps managed forests healthy and productive over time. And often, it’s variety, he says: sunlit gaps in the canopy, trees of different ages, and—critically—an abundance of stumps, logs, branches and twigs on the forest floor. Just as in farmlands, debris like this reduces erosion, stores carbon, recycles nutrients and creates habitat for animals and understory plants. But in the quest for new fuel sources, it has been dubbed “waste” and ripe for the taking—much to Mladenoff’s alarm.
“From my standpoint, we’ve spent much of the last 20 years learning that we need to be leaving more wood behind in the forest after harvesting, and now all of a sudden the movement is: We want to take the rest,” he says. “It’s in total conflict with what we know ecologically.”
Not that the intentions here are bad. In an effort to replace coal with cleaner, renewable energy sources, many states have built power plants that can burn plant-derived materials instead, such as scrap lumber, debris from timber harvests and cornstalks. Environmental groups have praised the move, but the power plants’ ravenous appetite for fuel is creating other problems. A few years ago, for example, Wisconsin set a guideline stating that loggers need leave only one ton per acre of woody debris behind after cutting trees—some three to eight times less than after a normal harvest, or what amounts to “a bunch of pen-sized twigs scattered around in an acre,” Mladenoff says.
“What does it mean, then, if we can basically remove as much debris as possible?” he asks. In a series of studies in different parts of northern Wisconsin, he and a group of collaborators are now trying to find out. Similar to Kucharik’s work at Arlington, they’re examining the effects of intense debris harvesting on forest carbon: How much is released and how much is stored? They’re also measuring the amount of nitrogen forests lose when different amounts of biomass are taken—data that Mladenoff will then use to model impacts on forest productivity long-term.
And that’s the easy part, he adds. Just as worrying, but much harder to assess, is how simplified forest landscapes scoured clean of woody debris will affect the birds, insects, amphibians and mammals that rely on it for habitat. “People are just starting to think about that,” he says.
So does this mean the practice is wrong? Mladenoff definitely has his views on the subject, but he also thinks “right” or “wrong” is somewhat beside the point. “Biofuels may not end up making sense ecologically or economically, but society may still decide to pursue them. Maybe it’s better than going to war with Iran over oil, for example,” he says. “But the way I put it is, we need to know what the trade-offs are. Then society can make a policy decision.”
Jackson agrees, noting that mixtures of plants chock-full of ecological benefits may be something of a mixed bag as well. “It’s pretty clear from our two years of data that the extra services we may get from a diverse system are likely going to be offset by lower productivity overall,” he says. Few, if any, bioenergy crops will probably ever rival King Corn’s sheer biomass-growing power, for one, especially on rich soils like those at Arlington. But even monocultures of switchgrass often are more productive, easier to manage—and thus more attractive to farmers—than mixtures of species.
So what’s needed now is a full accounting, Jackson says. “Okay, the diverse system is less productive. But what does it do to greenhouse gas emissions, carbon accumulation, nitrogen retention?” he says. “Are we seeing extra benefits there, or is maybe the switchgrass monoculture just as good on all those accounts as diverse prairie?”
He believes the sustainability group’s biggest contribution will be to quantify all those trade-offs and present them to farmers, policy makers, land managers and citizens in a way they can easily grasp. And then it will be up to us to decide: Is fuel the utmost goal? Or are ecosystem services also worth pursuing—and paying for? Because like the ladybeetle, what the agricultural landscape looks like, how it functions, matters to us. But unlike her, we have a say in shaping it.