Twenty years ago, in the last year of the old millennium, a book about “wild swimming” became a surprise bestseller.

Subtitled A Swimmer’s Journey Through Britain, Waterlog combined the classic quest narrative with a new way of writing about the natural world, the product of author Roger Deakin’s lifelong passions for swimming and nature.

Waterlog helped to turn wild swimming from a niche interest into a nationwide obsession. It also kick-started the movement that would come to be known as “New Nature Writing”.

New (as opposed to Old) Nature Writing is not easy to define; but it usually puts the author at the centre of the experience, by celebrating what the cultural historian Joe Moran calls “our everyday connections with the natural world”.

Twenty years on, and every bookshop has prominent displays of the latest crop of books, which this year include Robert Macfarlane’s Underland, Brigit Strawbridge Howard’s Dancing with Bees, and my own modest offering, The Twelve Birds of Christmas.

Despite the success of this publishing phenomenon, there are undercurrents of discontent bubbling beneath the surface. The world of nature writers may not seem the obvious place for arguments about gender, race and politics to play out but all these issues are being fought over behind the scenes. This matters because for people to engage with nature, as all authors surely want their readers to, those readers need to feel a connnection with the subject matter and how the story is told.

British author Helen Macdonald poses with her Biography Award winning book ‘H is for Hawk’. Photograph: Justin Tallis/AFP/Getty Images

One perennial issue is about whether the genre is being colonised by white middle-aged men at the expense of other voices. In the last decade many books with the greatest impact and highest sales have been written by women. They include H is for Hawk, a moving memoir of grief by Helen Macdonald, and The Outrun, Amy Liptrot’s powerful account of how nature’s redemptive powers helped her overcome her substance addiction. Both titles were not just critically successful, but commercial hits too.

But even if the gender balance is improving, most nature writers still come from a close-knit group who, with a few notable exceptions, are mainly middle-class, middle-aged and white.

Yet browse YouTube, or check out social media, and you’ll soon discover that young writers are writing about nature: but mostly via blogs and videos, as you might expect from this generation. And, in a welcome about-turn, social media is now proving a gateway into book publishing. One 15-year-old from Northern Ireland, Dara McAnulty, has just been commissioned by the independent publisher Little Toller to write his first book: Diary of a Naturalist. Based on his blog, which has attracted praise from TV presenter and activist Chris Packham, the book will chronicle the unique way Dara – who is on the autistic spectrum – experiences the natural world.

You can't write poems about the natural world now unless it's in an environmental context Simon Armitage, poet laureate

At the same time, Mya-Rose Craig, the 17-year-old British Bangladeshi known as Birdgirl is fighting hard to redress the lack of visible minority ethnic (VME) writers .

Mya-Rose points to the barriers these writers face when trying to gain access to the industry: “Mainstream publishers need to allow VME nature writers to write honestly and in their own voice. Too often the expectation is they must conform to the norms of current nature writing, in terms of both content and style.”

One exciting new voice is that of Zakiya Mackenzie, a young woman born in London and raised in Jamaica, who earlier this year became one of Forestry England’s first two writers-in-residence. Meanwhile, The Willowherb Review – named after a particularly tenacious wildflower – now provides an online platform for emerging writers of colour, including Craig, who featured in the first issue.

A greater diversity in nature writing, whether through gender, age, ethnicity or class, is both welcome and essential. But all writers, whatever their background, must now grapple with another issue – the question of how far should they engage in the environmental catastrophe.

Author Robert MacFarlane in 2012. Photograph: Andy Hall/The Observer

In 2015, two of the big beasts of nature writing – Mark Cocker and Macfarlane – clashed in the pages of the New Statesman. The debate was whether writers have a duty to engage with the very troubling environmental reality or whether it was OK to keep the context of nature writing as something personal and private, rather than political.

The poet laureate, Simon Armitage, recently entered the debate, stating that poems about the natural world need to tackle climate change face on. “You can’t write poems about the natural world now unless it’s in an environmental context,” he said.

In my view, writing about the natural world can still be approached in very different, yet equally valid, ways. The Lost Words, Robert Macfarlane and Jackie Morris’s stunning, large-format volume, celebrates the vocabulary of nature through poetry and paintings. At the other end of the scale, my favourite book of the year is Benedict Macdonald’s Rebirding: a clear and detailed vision on how to bring back Britain’s lost wildlife, while at the same time restoring rural economies. Both The Lost Words and Rebirding – one from an established writer and well-known artist, the other by a young newcomer – can and should be able to co-exist, if New Nature Writing is to remain a broad church.

Waterlog appeared at a time when classic travel writing, which had dominated non-fiction for so long, was on its way out, because readers no longer needed privileged authors to take them on journeys to places they could visit and experience for themselves. If New Nature Writing is not going to go the same way, and decline into irrelevance, it must continue to adapt to the new challenges.

But in doing so, we all need to remember one thing. That in an increasingly polarised and intolerant world, the real fight is not among ourselves, but against those who, in pursuit of privilege, wealth and power, seek to destroy everything we hold so dear.

• Stephen Moss is a naturalist and author, whose latest book, The Twelve Birds of Christmas, is published by Square Peg. He is course leader on the travel and nature writing MA at Bath Spa University