James Rebanks’s story of his family’s farm in the Cumbrian Fells, English Pastoral, has won the Wainwright nature writing prize, praised as a “seminal work which will still be celebrated in 50 years”.

The follow-up to Rebanks’s memoir The Shepherd’s Life, English Pastoral tells of the home in the Lake District, where his family have lived and worked for more than 600 years, and how he began to farm in a more sustainable way. It was up against titles including Raynor Winn’s follow-up to The Salt Path, The Wild Silence, for the award, which is named after writer and fellwalker Alfred Wainwright and which goes to the book that “most successfully inspires readers to explore the outdoors and to nurture a respect for the natural world”.

Rebanks’s win comes as sales of books about the natural world soar: according to Nielsen BookScan, natural history sales totalled £2.8m in July and August this year, up 21% on the same period last year, and 31% on 2019.

“James Rebanks adores his home and job and that’s reflected in his writing. His message of respect for the old ways and understanding of the complexities of farming for the future make this a really important book. And it’s all couched in beautiful prose,” said judging chair and presenter Julia Bradbury. “The writing is accessible, heartfelt and poignant, and it conveys a message of achievable change. Rebanks’s passion will carry any townie through the joy and hardship of fell farming.”

Rebanks, speaking from the top of Glenridding on his way to see some lambs, said he was grateful to win the award. “It probably took me 20 years to write my first book, because I started thinking about it when I was 17 and I was about 40 by the time I did it. This one took three or four years of work,” he said. “The first book was very much about who we are and why I’m proud of the people I’m from and the landscape I’m from, and what our lives are like. It meant a lot to me to try and get that in front of other people.”

English Pastoral, he said, was “probably a more grown-up effort … It’s me reckoning with all the big stuff that’s going on at the moment, and some of our flaws and limitations – the complexities of what it actually is to live on the land. They’re competing needs – we need food, and we need nature, and we need trees and fields. It’s all quite complicated,” said Rebanks. “So it’s all about a quite small farm, and quite a small life and a small community, but I think it touches on a lot of the bigger issues.”

The Wainwright awards ceremony on Tuesday evening also saw Merlin Sheldrake win the Wainwright global conservation and climate change prize for Entangled Life, his exploration of the hidden world of fungi.

BBC Countryfile presenter Charlotte Smith, who chaired the judging panel for the global conservation award, said Sheldrake’s book “blew us away”. “It contains extraordinary descriptions of how extraordinary nature is, and the implications around soil carbon and fungi as a plastic replacement are huge. Beautifully polished, it is a very important piece of work,” said Smith. “Astonishing to find a book which after reading, forced us to think about our world view of conservation every day.”

Sheldrake said he was “delighted and surprised” to win. He hadn’t considered writing a book, he said, until he was approached by literary agents, and then the idea “grew on me”.

“It struck me that fungi are not only a neglected kingdom of life and there’s lots of opportunity to talk about them to a more general audience, but I realised that the book could be quite wide-ranging because fungi live their lives enmeshed with their environments and with other organisms, and you can’t think about them for long without also thinking about where they’re living and who they’re living with,” he said. “It’s just wonderful to see so many people interested in learning about fungi. I’m wonderfully, happily surprised at how interested people seem to be in the subject. Its time has come.”

A prize fund of £5,000 will be shared by Sheldrake and Rebanks, who join former winners including Dara McAnulty, who took the award last year for Diary of a Young Naturalist, and Amy Liptrot who won for The Outrun.