Harshly lit by the bluing hard sun that February hoards for itself, college gardens in winter both promise delights to come and hold beauty at hand. Emmanuel College’s garden holds for me a russet-branched birch tree, a paddling of ducks, and nature writer and English fellow Robert Macfarlane, who wants to introduce me to trees.

The crown of Emmanuel is its Japanese Plane Tree which roots again and again wherever it throws its branches down. The tree has been there for hundreds of years, watching the station and the college, wintering its leaves down on heads and buses and bikes. We walk in and around it for a while, feeling our smallness.

Retiring inside, Macfarlane describes his love of wild places as going back as long as he can remember, to his childhood “in deep England at the end of a country lane in Nottinghamshire” and holidays spent on Scottish mountainsides.

Wildness is a difficult term, uncertain of its place in a "post-natural world”. Macfarlane says he began his book The Wild Places with a “blithe ignorant definition” of the wild as “a place absolutely beyond human influence, which is untenable in the British context and almost disposed of in a global context". However, he says, "if you dismiss with the deeply troublesome idea that the wild is some pure zone or realm then it becomes much more interesting.”

While attracted initially to “very remote and high places”, Macfarlane has increasingly been interested in the idea of the wild as a complicated and difficult place: “I recently spent three or four days under Paris in the catacombs there working out what a city is like from the inside and underside out and up”.

Recourse to nature has long been held as a tonic for trauma. Might it be – whisper it– that most “culturally contraband” of words 'spiritual'? Macfarlane says he finds himself reaching for a “semi-sacred language” to describe the gift and good of landscape: “I am interested in the very private processes of consolation and grace and happiness and beauty and encounters with wonder that go on throughout the country on a personal moment by moment basis.”

David Cameron is a man well aware of the consolatory abilities of landscape. Macfarlane charges him with “encouraging a cosy, cupcakeified, Hunter-wellied vision of the rural landscape, with which the brutalities of austerity politics can usefully be softened and foliaged". He suggests that "it serves as a kind of green ketamine in the water, a means of encouraging us all to Keep Calm and Carry On".

Macfarlane is gently but firmly indignant at this posturing, noting that former environment secretary Caroline Spelman "tried to sell off the forests" while "Owen 'Badgers Moved My Goalposts' Paterson" has proposed an "offsetting scheme for ancient woodland which is earmarked for destruction, as if a 400-year-old oak forest is a fungible asset.”

Macfarlane’s books, which are made up of the lightest of lyrics, the most heady of myths and warmest of histories all at once, do not come to him easily: “I re-write obsessively. Each sentence will be re-written fifty or sixty times and my books take me five years.”

“Light is a non-verbal medium and scent and air and atmosphere and all the things that make up what we call landscape," he explains. "Cliché is always prowling at the perimeter because so many people write about landscape and landscape has attracted this layer of cliché which clings to it and is hard to get through”.

Macfarlane takes great pleasure in the layered density of place names and a sense of knowing your own landscape: “Language is a way of bringing us into careful intimacy with places”. He is an appreciator of the small beauty of colloquial words and names. In Sussex, a “smeuse” is the small hole left in a hedge where an animal has moved through it repeatedly and thawing is given the “compressed poetry” of “ungive”– “that still stops me short”.

The acknowledgements at the back of his latest book The Old Ways include a healthy list of musicians – “I’m a total Johnny Flynn fangirl”. The fruitful conversation with other artists into which Macfarlane’s work can be brought is emblemised by the writer’s real life walk along Holloway Road with folk musician Frank Turner, talking about “the strange way that a city street can possess the same layered density as a deep Dorset lane”.

These close artistic ties include a friendship with the sculptor Steve Dilworth, who made Macfarlane a sculpture of “a dead starling encased in dolerite with bronze legs and a vial of ink gagging its beak open”. He pauses: “I haven’t subjected it to intense interpretation”.

Macfarlane was the chair of the 2013 Man Booker Prize jury, a job which allowed him to “read a year’s dreams and visions of writers from around the Anglophone world”. But how to even begin to judge a book? He laughs and with upturned palms says: “You read it”.