Ruth Padel has described herself as a writer "formed by the 19th century". "There's something about the mindset of that time: a curiosity, a desire to make links. It appeals to me deeply." The Mara Crossing  a broad-ranging meditation on all things migratory  is certainly concerned with the making of links. But it's also about drawing distinctions, or, more precisely, walking a nervous line between these impulses. Bifurcation  between poetry and prose, human and animal, privilege and under-privilege, and, crucially, art and science  is at the heart of the collection and powers its explorations of journeying. This is a book of raw interfaces and unnerving encounters, not comfortable oppositions of black and white.

Padel introduces her mixed-media approach in terms that understate its complexity: "The prose interludes" which preface each series of poems were, we are told, written after the poems and are designed to "set them in context". But there's more going on here than a simple duet of artifact and exposition. One of the stated objectives of the book is "to hold migration up to the light from a lot of different angles"; one of the unstated objectives is to hold poetics to the same scrutiny, and to weigh the implications of how art acts on the "real".

The book opens with biology in a series of poems that engage with the splitting, replication and migration of cells  the "soap opera of relationships, breaking bonds and creating new ones" on which "the spread of life depends". As poems, these are problematic: the relationship with the prose is repetitive rather than transformative, the use of specialist language hobbles the rhythmical impetus of the writing, and the poems don't really lift off or add anything to the factual material preceding them. While one of the most impressive features of the book is a reach which means every reader will come up against areas of knowledge, and associated language, with which they are unfamiliar, Padel herself doesn't seem comfortable enough with the world of "cyanobacteria" and "helicase" to rise to the challenge of imaginative response.

When it comes to animals, though, there's a significant change with magnificent poems such as "Nocturne" and "Barnacle's Lovesong to Humpback Whale"  the former a triumph of imagistic ingenuity, the latter a bizarre inhabitation of the barnacle's mind. Padel has spoken of both science and poetry as "modest" disciplines. This idea plays out in "Nocturne", where the act of comparing jellyfish to the contents of the unconscious  "the unnamed / that is always there under the surface"  co-exists with a torrent of imagistic description which is at once self-defeating and self-delighting. The jellyfish are "translucent udders", "pulp-and-tinsel dribbles", "the book of the sea shredding as it unfolds": the list goes on and on, as though either the poet couldn't stop, or else each single image seemed somehow deficient. Similarly, later in the collection, art is enshrined in the products of "itinerant stained-glass makers" and "Sun scatters, uneven as heartbreak, / through imperfections in everything they make".

But art is also arrogant: to bring "other worlds  to life in glass", the glass-makers have to put "wood and sand" through a complicated process of "heating, cooling, melting". Likewise, the poet of "Nocturne" arrives at "true" representations only by converting what is seen into pictures that the human mind can work with  "pulp-and-tinsel-dribbles" and so on. This is what imagery does and how poetry works: it makes things "True, perhaps. Or just truer" by a process of making them other, an imaginative "occupation" that plays fast and loose with the facts. Padel tussles with this knowledge throughout  with the awareness that there are uncomfortable links between art and colonisation, and art and violence, and with the paradoxical truth that we can gain access to other perspectives only by filtering them through the networks of our own.

Some poems, accordingly, opt for a plain register, with minimal "arrangement" or interference. It's not possible to conjure the experience of animals without sinning through usurpation, but poems in the voices of human migrants, such as "The Desert and the Sea", tell their stories straight. Others, such as "Maltese Fishing Boat and Broken Net" and "The Prayer Labyrinth", present the reader with direct challenges  "What would you do?"  or else use the second person to force empathy with the predicaments of others.

Padel sums up migration as an undertaking that "moves you into a disorientated world  You have to start putting things together in a new way." This is true of the stories she tells and the responses she provokes in The Mara Crossing, but also of her own formal and ethical imperative in writing the book the way she has. "No poet", she says, "is a stranger to estrangement"; few, however, are willing to put the medium they love so stringently to test to see this through.

 Miriam Gamble's The Squirrels Are Dead is published by Bloodaxe.

Ruth Padel has described herself as a writer "formed by the 19th century". "There's something about the mindset of that time: a curiosity, a desire to make links. It appeals to me deeply." The Mara Crossing  a broad-ranging meditation on all things migratory  is certainly concerned with the making of links. But it's also about drawing distinctions, or, more precisely, walking a nervous line between these impulses. Bifurcation  between poetry and prose, human and animal, privilege and under-privilege, and, crucially, art and science  is at the heart of the collection and powers its explorations of journeying. This is a book of raw interfaces and unnerving encounters, not comfortable oppositions of black and white.

Padel introduces her mixed-media approach in terms that understate its complexity: "The prose interludes" which preface each series of poems were, we are told, written after the poems and are designed to "set them in context". But there's more going on here than a simple duet of artifact and exposition. One of the stated objectives of the book is "to hold migration up to the light from a lot of different angles"; one of the unstated objectives is to hold poetics to the same scrutiny, and to weigh the implications of how art acts on the "real".

The book opens with biology in a series of poems that engage with the splitting, replication and migration of cells  the "soap opera of relationships, breaking bonds and creating new ones" on which "the spread of life depends". As poems, these are problematic: the relationship with the prose is repetitive rather than transformative, the use of specialist language hobbles the rhythmical impetus of the writing, and the poems don't really lift off or add anything to the factual material preceding them. While one of the most impressive features of the book is a reach which means every reader will come up against areas of knowledge, and associated language, with which they are unfamiliar, Padel herself doesn't seem comfortable enough with the world of "cyanobacteria" and "helicase" to rise to the challenge of imaginative response.

When it comes to animals, though, there's a significant change with magnificent poems such as "Nocturne" and "Barnacle's Lovesong to Humpback Whale"  the former a triumph of imagistic ingenuity, the latter a bizarre inhabitation of the barnacle's mind. Padel has spoken of both science and poetry as "modest" disciplines. This idea plays out in "Nocturne", where the act of comparing jellyfish to the contents of the unconscious  "the unnamed / that is always there under the surface"  co-exists with a torrent of imagistic description which is at once self-defeating and self-delighting. The jellyfish are "translucent udders", "pulp-and-tinsel dribbles", "the book of the sea shredding as it unfolds": the list goes on and on, as though either the poet couldn't stop, or else each single image seemed somehow deficient. Similarly, later in the collection, art is enshrined in the products of "itinerant stained-glass makers" and "Sun scatters, uneven as heartbreak, / through imperfections in everything they make".

But art is also arrogant: to bring "other worlds  to life in glass", the glass-makers have to put "wood and sand" through a complicated process of "heating, cooling, melting". Likewise, the poet of "Nocturne" arrives at "true" representations only by converting what is seen into pictures that the human mind can work with  "pulp-and-tinsel-dribbles" and so on. This is what imagery does and how poetry works: it makes things "True, perhaps. Or just truer" by a process of making them other, an imaginative "occupation" that plays fast and loose with the facts. Padel tussles with this knowledge throughout  with the awareness that there are uncomfortable links between art and colonisation, and art and violence, and with the paradoxical truth that we can gain access to other perspectives only by filtering them through the networks of our own.

Some poems, accordingly, opt for a plain register, with minimal "arrangement" or interference. It's not possible to conjure the experience of animals without sinning through usurpation, but poems in the voices of human migrants, such as "The Desert and the Sea", tell their stories straight. Others, such as "Maltese Fishing Boat and Broken Net" and "The Prayer Labyrinth", present the reader with direct challenges  "What would you do?"  or else use the second person to force empathy with the predicaments of others.

Padel sums up migration as an undertaking that "moves you into a disorientated world  You have to start putting things together in a new way." This is true of the stories she tells and the responses she provokes in The Mara Crossing, but also of her own formal and ethical imperative in writing the book the way she has. "No poet", she says, "is a stranger to estrangement"; few, however, are willing to put the medium they love so stringently to test to see this through.

 Miriam Gamble's The Squirrels Are Dead is published by Bloodaxe.