Roger Deakin has something of the status of a secular saint. Writer, broadcaster and campaigning environmentalist, co-founder with Sue Clifford and Angela King of the pressure group Common Ground, he walks the pages of this book like a Franciscan friar.

As he perambulates the boundaries of his Suffolk parish, bound by a vow of holy poverty, making do and mending, collecting firewood, gathering wild fruit and berries, he challenges the human beings he meets to speak to him. But they mostly disappoint, armoured in their four-wheel drives or behind the smart new name-boards of their converted barns and done-up cottages (“nobody ever had house signs because they knew their neighbours anyway”), mourning the passing of the old sociability, the mutual interdependence of rural life. His solitary, almost feral, existence is shared with the creatures who cohabit the same woods and fields. He curls up like a cat in the roots of a tree to sleep, breaks off from writing his diary to allow safe passage to a lost ant.

When he goes to London he finds a country spider still asleep in his haversack, and carefully carries it about all day before restoring it to its own habitat on his (their) return to Suffolk. The prefix “eco” (as in the word ecology) is derived from the Greek word oikos, meaning “home” or “dwelling place”, and Notes from Walnut Tree Farm centres on Deakin's own home, the village of Mellis, with its common and its associated lanes and “long greens”, which he traces like the human equivalent of the badger paths he sees in the low light of a winter sun radiating from the mud hill fort of a badger sett.

His own habitats include the moveable shepherd's hut where he sleeps on summer nights, the railway wagon where he naps and is awoken by the vibrations of a roe deer scratching its rump, and above all the ancient wood-framed house that gives the book its title, restored from ruin 30 years ago and still shared with the insects, birds and other creatures who inhabited it before he did.

Deakin is no saint, however: randy, ranting (against planners, dogs, heritage trail-makers), resolutely secular (when he visits his Suffolk neighbour Ronald Blythe, officiating in church on a Sunday, Deakin waits in the churchyard until the service is over), he remains more angry young man than grumpy old one. “I don't have a problem with anger,” he says, “the main problem I have is that most people - society in general - are not sufficiently angry about those things that upset me”: the careless destruction of the countryside, the relentless erosion of local disinctiveness, the severing of the bond between man and his environment.

“Books are like seeds,” he says. “They come to life when you read them, and grow spines and leaves.” Those looking for a misery memoir of Deakin's fight against the aggresssive brain tumour that killed him in 2006 will be disappointed. The book ends as it began, at new year, in the luminous present, with Deakin walking his beloved common in the darkness and the wind, listening, and watching the shooting stars.

Notes from Walnut Tree Farm by Roger Deakin
Hamish Hamilton, £20; 320pp Buy the book

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