MATTERDALE, England — Britain's rock-star shepherd and best-selling author, James Rebanks, is out at the family farm, giving the tour, waxing rhapsodic about his manure. The glory of it — of the crumbly, muffin-top consistency of a well-made plop from a grass-fed cow.

“Has anyone in your life ever truly explained grasses to you?” he asks. And we think, not really.

It’s not just ruminant digestion. Don’t get the man started on soil health. Rebanks is a soil geek, with the zeal of the convert. We’re soon on our knees, grubbing in the dirt. Sniffing. He’s distracted by a red-tailed bumblebee, then by the surround-sound of birdsong. “I don’t trust a quiet farm,” he says. “It should be noisy with life.”

Rebanks represents one possible future for farming, which is set to be transformed in the promise of a post-Brexit, zero-carbon world. The British government plans to strip away all traditional farm subsidies and replace those payments with an alien system of “public money for public goods.”

What are these public goods? Not food. Bees! In 21st-century Britain, the goods will be clean water, biodiversity, habitat restoration, hedgerows, pretty landscapes, wildflowers, flood mitigation and adaptation to climate change. All the stuff the public wants, according to the pollsters.

This transformation could be huge: Farmland is 70 percent of England’s landscape and produces 10 percent of its greenhouse gases. There is no net-zero-carbon future without farmers.

As the best-known farmer in the whole of the United Kingdom, Rebanks finds himself at the center of this transition. In agriculture circles, he’s a super influencer, famous for his Twitter feed. He has nearly 150,000 followers, who check for his posts and postcard-perfect videos and photos of his idyllic home in England’s poetic Lake District and the doings of his beloved Herdwick sheep.

The shepherd riffs on the circle of life, the frenzy of lambing season, the deliciousness of grilled mutton and the wisdom of sheepdogs — speckled with rants against the alleged ruinous stupidity of industrial farming “where the field has become the factory floor.”

In his tweets as well as in person, the 47-year-old Rebanks is by turns rapturous, frustrated, hopeful and angry. He cannot fathom that the planet, and his little corner of it, has been so messed up. He also cannot make up his mind whether we are doomed or just might pull through, a feeling that resonates with many.

He wrote two books about all this, both international bestsellers. The latest, published to stellar reviews this month in the United States, is “Pastoral Song: A Farmer’s Journey.”

On one level, the book is about how cheap food culture, globalization and super-efficient, ­hyper-mechanized, highly productive modern farms (giant monocultures of beets, wheat, corn) are terrible for nature (insects, rivers, climate) and our health (obesity, diabetes) and our farmers (indebted, pesticide-dependent, stressed).

On a deeper level, though, the pages are about healing, about how one farmer in Cumbria is trying very hard to turn his landscape into a sustainable, profitable little Eden by deploying both ancient and cutting-edge techniques.

Through his books, his online ubiquity, his lectures, interviews and tours, Rebanks has become the man of the moment in British farm policy.

When he started on Twitter a decade ago, he was an anonymous bloke with a chip on his shoulder, a history degree from Oxford, an inherited farm, a small herd of sheep. Now, he’s a guru, whether he likes it or not.

British politicians make the pilgrimage to see what he has done. So do British journalists. He has made the cover of the Financial Times magazine and is the subject of a 30-minute documentary on the BBC. He pens guest columns for the right-wing Daily Mail and the left-wing Guardian.

A fellow farmer observed without rancor last year: “When turning on the TV, listening to the radio or opening a newspaper, it was impossible to avoid upland farmer James Rebanks espousing his views on the future of sustainable farming as he publicised his new book.”

With Brexit a done deal and Britain free from the European Union’s Common Agricultural Policy, the government is embarking on the biggest change in the management of its countryside since the end of World War II.

No longer will farmers live on the Basic Payment Scheme. They will be paid for those new public goods; the old subsidies for “food security” will end. It is a radical experiment, to be carried out on a national scale.

Yesterday’s farms grew food and outgassed methane.

The farms of tomorrow will grow food and sequester carbon.

Or at least that is the idea. Rebanks is supportive, but wary.

British farmers, like their counterparts elsewhere in Europe, have subsisted for three generations on subsidies. Without the dole, government figures show, 42 percent of all farms here would operate at a loss. Most small operators wouldn’t survive without the checks. The payments — $3 billion annually — are to be phased out over the next seven years.

Rebanks worries that many traditional farmers on less productive land won’t make the transition and will be forced to retire or sell. The government concedes this is a likely outcome for some.

If taxpayers and consumers don’t want to pay the high costs of regenerative, sustainable, zero-carbon farming, he fears, “then all the little guys will just go bankrupt,” and big farms “will just turn up the intensity dial and fiddle with nature around at the edges.”

As presented, Rebanks doesn’t think the plan is nearly smart enough or big enough, or that the public understands how much it will cost to have a real impact for farmers, nature and climate. He thinks $3 billion year is “a drop in the bucket.”

A few thousand pounds here and there to plant some wildflowers at the edge of fertilizer-dosed fields? “It’s not going to cut it, and we’re deluded if we think it will,” he stressed on a recent morning.

If anyone can make the switch to this new system of “public money for public goods,” surely it should be Rebanks. He seems more than halfway there already.

His Racy Ghyll farm is green and gorgeous, yet at only 185 acres, it’s smaller than it looks on the Internet. The majority of British farmers work land of similar size.

Rebanks and his border collies tend four flocks totaling about 450 Herdwick sheep this summer. That’s his main income. He also has 15 Belted Galloway cows, a stocky, fat-bellied breed that can overwinter outdoors. He bought the cows not just to sell their beef, but also for the animals to trample the fields with their hoofs, to break up and improve the soil.

Three dozen chickens live in a hen house on wheels, which allows him to easily spread their manure around, and he puts the eggs out on the lane for customers who leave a few coins. He grows hay, too, harvesting it later in the season to give the curlews a chance to raise their chicks.

His critics in Britain, along with some farmers in the United States and Australia, have suggested that Rebanks is a nostalgic romantic. A hobbyist. A dilettante.

He disagrees. His family has been shepherding in Cumbria for 600 years. His methods — moving sheep between the communal hilltop fells and the valley below — would be recognizable to the Vikings, who did the same when they settled here more than a millennium ago with a similar breed of hearty sheep.

Over the past 10 years, with help from conservationists and supporters, he and his family — his wife and four kids — have “re-wiggled” a drainage ditch and created a natural stream plus wetland.

They’re planting 25,000 saplings. There were no ponds on the property before. There are 25 now, with otters. Three miles of hedgerows have been restored and 30 acres revived as a wildflower meadow.

A botanist told Rebanks that the farm now supports 200 species of flowers and grass.

Based on study and advice, Rebanks has radically altered his grazing patterns, moving his animals much more frequently from pasture to pasture. “There’s no vegan grassland,” he said. The cows and sheep have to turn over the soil.

He’s chopping up the farm to smaller and smaller fields — “it’s all hedges and edges, which is good for nature.” He estimates he has taken 15 percent of his farm out of active production.

“Listen, the truth is there must be some letting go,” he said. “You can’t drain it all and use it all for farming or grazing. You have to set some aside.”

That setting aside should be compensated, he believes. Despite many laws, protections and preserves, England’s farmland birds have declined by 57 percent since 1970. The summer swarms and buzz of insects are disappearing. The story is the same in Europe and the United States.

“So it’s lovely here, okay? But we don’t need a little bit of lovely somewhere, we need a lot of it everywhere,” he said.

In the post-Brexit world of free-trade deals, British farmers will not be able to compete, because the British landscape doesn’t allow for large-scale or intensive agriculture without grave damage to its remaining biodiversity.

Asked whether this calls for protectionist policies, Rebanks said it certainly does — and that the public will have to decide how seriously the twin crises of climate change and biodiversity loss should be addressed.

“Pay me to do my regenerative farming,” he said. “Or go into a shop and pay me twice as much for my steak.”