Flight Behaviour, By Barbara Kingsolver

Everything fits together in this beautiful study of eco-scepticism, lepidopterology and the subtleties of human behaviour

Following her Orange Prize-winning historical novel The Lacuna, Barbara Kingsolver returns to a contemporary canvas with this hugely ambitious tale about climate change set in the mountain pastures and forests of Appalachia. Dellarobia Turnbow (her ma picked her first name out of a women's magazine) is a restless young farm wife, five-feet-nothing with flame-coloured hair, who gave up her ambitions at 17 to marry in haste after falling pregnant. A miscarriage, 10 quarrelsome years and two children later, tied to a man she can't respect and subsisting on his parents' run-down farm, she's desperate to escape.

One November morning, she marches up the mountain in calfskin fashion boots, determined to throw her "good life away" on a reckless tryst with a younger man, the latest in a line of casual flirtations. But near the top she's met by an astonishing sight: a forest that appears to blaze with flame, "a vision of glory to stop her in the road". This almost biblical revelation with its "unearthly beauty" is enough to dispatch her homewards, all thoughts of adultery abandoned.

What Dellarobia has seen is millions of orange monarch butterflies resting in the trees ("King Billies", her ma-in-law dubs them); refugees from their usual over-wintering quarters: a mountain in Mexico recently devastated by unprecedented rainfall. Though she is not religious herself, the discovery invests Dellarobia with awe in the eyes of her God-fearing community. As news of the butterfly colony spreads, it brings tourists, welcome for their money, television crews, who distort the story, and, most crucially, a team of scientists led by a fascinating black American ecologist by the name of Ovid Byron.

Byron has made monarchs his life's work and he explains to Dellarobia how their flight from Mexico is not the great miracle everyone thinks, but a grim symptom of global warming. The butterflies, he warns, might not survive. But "I'm not here to save monarchs", he tells her. "I'm trying to read what they are writing on our wall."

Much of Kingsolver's remarkable body of work, here as elsewhere, links big scientific themes with fine subtleties of human behaviour. She moves easily between the grandiose and the personal. Flight Behaviour is perhaps closest to her 2000 novel Prodigal Summer, with its small-farm setting and its fears for the natural world, but now her warning about the precariousness of our ecosystems is almost shouted. Ovid spells out the science clearly: how the number of carbon molecules the atmosphere can hold to maintain the ordinary thermal balance has already been exceeded, and still mounts. On occasion this message threatens to overbalance the novel, but the author always pulls back in time.

Her field of inquiry is climate change denial; why so many deny that climate change is happening, or ignore it in the hope that it will go away. Perhaps it's a version of flight behaviour. She lays part of the blame on the scientists. Ovid can explain matters clearly enough to intelligent, observant Dellarobia, whom he employs to help monitor the butterflies, but she upbraids him for failing to connect with ordinary people. "Maybe your medicine's too bitter … Maybe you're writing us off, thinking we won't get it," she accuses. Interviewed by a TV reporter who's after the butterfly miracle angle, Ovid fails to meet her halfway. Instead, his erudite polemic, filmed on a cell phone, goes viral online.

Dellarobia ably carries the narrative. She understands her community, but can stand back from it, too. When Cub, her doormat of a husband, mumbles "Weather is the Lord's business", and, of Ovid, "He's not from here, that's the thing", she appreciates that the educated Ovid "would have no inkling of the great slog of effort that tied up people like her in the day-to-day". She and Cub and his stubborn parents strive to pay the bills. Cub's father wants the butterfly forest to be felled for logging to pay off farm debts made worse by a summer of rain. Still, she has sympathy with Ovid's despairing "unscientific" thought: "What if all human effort amounted basically to saving a place for ourselves to park?"

During the course of the novel, Dellarobia, like the butterflies, struggles to survive in conditions she's not made for. She's tireless in her mothering of six-year-old Preston and toddler Cordelia, battles with her tough, bitter mother-in-law, Hester, and engages finally with the difficulties at the heart of her marriage. Kingsolver demonstrates an insider's knowledge of the farming life. Her descriptions of the everyday – shearing day, immunising the sheep – are surprisingly fascinating. There are many moments of lightness, especially from Dellarobia's wild schoolmate Dovey, and of great beauty, too. It's impossible to watch the dancing butterflies with Dellarobia and her children, to see "wonder and light come into her daughter's eyes", the boy with "his arms outstretched as if he might take flight", and not be moved.

Rachel Hore's latest novel is 'The Memory Garden' (Simon & Schuster, £7.99)

Faber £18.99