“I had a long way to go with wasps and hornets,” Tawnya Kiernan told me, as her husband, Mike Kiernan, drove us north along Vermont’s iconic Route 100, past the ski town of Stowe; it was late August, and a few trees were showing just the faintest tinge of color. “They seemed so aggressive and mean,” she added. “They were not good ambassadors for pollination. But, the more you learn, the cooler they are.” What followed was a discourse on hyperparasitism, by which some wasps lay eggs in insects that themselves are parasitic on other insects, a process that sounds disheartening until you recollect that, for all that parasitism, these wasps—and flies, and bees, and butterflies—are also pollinating, which is to say finding ways to coöperate across species, indeed kingdoms, in a spectacular display of mutualism. “The pollinators move seeds around, in turn they get the energy to raise their young,” Mike said. They do two things at once.
We pulled off the two-lane highway and onto a short farm road, and then got out at an access gate along a wire fence that enclosed an eleven-acre field of solar panels. The reason we were there is that three years ago, when Encore Renewable Energy—a Burlington-based developer of solar arrays—set up the panels, it contracted with a nonprofit that the Kiernans started, called Bee the Change, to seed pollinator-attracting plants that are native to the area in the rows between them. The organization’s small crew tends more than twenty fields like this across the state, weeding and, at least once a year, mowing what they have planted so that it doesn’t grow so high it shades the panels. Most of the attention to “agrivoltaics”—use of one piece of land for both farming and for producing solar energy—has gone to more common agricultural practices, such as letting sheep graze between the panels. But at least fifteen states, including big players like Illinois, maintain solar-pollinator scorecards, which are used as accountability measures in the solar-development community. The theory is that we face two crises—climate change and the rapid loss of biodiversity—and that the same patch of land might be used to address them both.
The approach seems to be working. When the Kiernans are hired by a solar developer, it’s usually to plant on what was until recently a farm field; “the farmer has decided to take a dozen acres” and lease them to solar companies “to get a guaranteed income,” Mike said. Because the fields are typically monoculture and have been treated with pesticides for years, “the pollinator density is really low.” Mike uses a pollinator-counting method that involves walking on the margin of a field and counting unique pollinators for seven and a half minutes. Then a random-number generator tells him which row of solar panels to walk along, and as he walks he counts the pollinators he sees in seven and a half minutes, then adds the two numbers together. “On those abandoned farm fields, we might get a count of forty or fifty in fifteen minutes,” Mike said. “But now, once we’ve done our thing, you can see ten at a glance. You can see three hundred in fifteen minutes. You see a lot of them even this late in summer, during what we call a ‘dearth period.’ Wait till next month, when the asters come in!”
We saw, indeed, an extraordinary number of small insects flying in and out of whatever blossoms were available: goldenrod, mountain mint, evening primrose, black-eyed Susan. “That echinacea is pretty tired,” Mike noted, then pointed out a lacy thing resting on a fleabane blossom. “Here’s an ichneumon wasp,” he said. “It lays its egg inside the larvae of other insects—there are forty thousand identified species in this family of wasps. Here’s a fly in the family globetail—enormously important as a pollinator. That’s from the housefly family, a muscid. On a cold day like this, it’s mostly flies.” After bees, flies are considered to be the most important pollinators. While we spoke, Tawnya never stopped pulling weeds that the Kiernans don’t want in these fields, such as the aggressive yellow foxtail, an invasive plant that reëstablishes itself when equipment is brought to mow or service the fields, carrying the seed with it. “Or look at this ragweed—it could have thirty thousand babies,” she said, ripping it from the ground. “You just have to keep after it,” Mike said. “There are maybe thirty species that are problematic.” Then he saw a small stand of reed canary grass, which he refers to in a voice that makes you not like it at all. “Leave it alone and it might cover everything in six years.”
Under their scheme, plants like asters and echinacea are sown near the solar panels, because they don’t grow high enough to shade them. Taller plants, such as joe-pye weed, are sown in the middle. The soil under the panels is left in “dry shade,” Mike said, “which is always the gardener’s challenge.” But, usually, he added, enough moisture gets through to plant jewelweed. “It has a special relationship with hummingbirds—their wings can vibrate at ninety beats per second, and I’ve heard that the entire blossom can resonate, and it’s just dumping pollen on their heads.”
The Kiernans founded Bee the Change about a decade ago, when their kids left for college. (Mike is also an E.R. doctor in Middlebury, and Tawnya is a pediatrician, but their empty nest, they insist, left them with “no idea what to do with ourselves.”) They were interested in pollination, in part, because of time that Mike spent as a volunteer doctor in Haiti, a country where widespread deforestation (and ongoing damage from strong hurricanes) has dramatically depleted the number of pollinators. He observed that roughly a third of the patients he saw were nutrient deficient. “People are missing the B vitamins from fruit and vegetables. If you want to see a world without pollinators, that’s it.” As the nonprofit’s name implies, their first tools were honeybees; they installed hives in solar fields. But, the more they learned about biodiversity, the more they wondered whether this strategy was actually the best for the environment. Honeybees are domesticated and are so persistent and numerous—more than thirty thousand can live in one hive—that, in Mike’s words, they “can put too much harvesting pressure” on the plants. There may not be enough nectar left behind for all the wild pollinators, a complication that spells peril not just for them but for the plants they’re particularly adapted to. “There are more than three hundred and fifty native bee species in Vermont,” Tawnya said. So they stopped placing hives and started installing native plants that attract wild bees.
Mary Powell, the former C.E.O. of Green Mountain Power, who has been described in these pages before, was an early supporter of the program. “And maybe the most important cheeseburger I had in my life,” Mike said, was a decade ago when he met with Chad Farrell, the founder and co-C.E.O. of Encore Renewable Energy, which deploys medium-scale solar arrays—not rooftop solar, but not the sprawling fields in the Western states, either. Farrell has fifteen years of experience in solar development; most of his projects are in Vermont and Maine.
“In New England, you’re often looking at five-megawatt projects, which means maybe twenty-five acres,” Farrell told me when we spoke by phone earlier this month. “We’re at four or five per cent of our electricity coming from solar now in this country. In order to hit the President’s target of forty-five per cent of our electricity by 2050, we have to grow. And that means we have to deliver the most visually appealing, environmentally responsible projects possible.” In 2020, his company pledged to build all their projects with some form of agrivoltaics. In many cases, that’s sheep grazing. “Not goats,” he said. “Goats will try to eat the wires between the panels, and also to jump up on the panels, which is not good for either one.” Sheep, though, appreciate the shade that the panels provide and are “some of the best asset managers we have in the business, mowing the grass for us. They do their job exceptionally well, and all they want is forage and water, which we can give them.”
Pollinators are even easier animals, though—once the plants have established themselves, they don’t need more than an occasional mow. “We think solar is a good neighbor,” Farrell said. “It’s clean, it’s quiet, and if it increases pollinators it’s helping the whole community.” And so—at a moment when new fossil-fuel-funded schemes are reportedly spreading disinformation about renewable-energy programs—“it can help reduce the friction. It can lower the hurdles to get over, which of course translates into dollars and cents.”