This thesis examines selected speculative novels by Margaret Atwood, Ursula K. Le Guin, Doris Lessing and Marge Piercy. It argues that a specifiable ecological ethic can be traced in their work – an ethic which is explored by them through the tensions between utopian and dystopian discourses. The first part of the thesis begins by theorising the concept of an ecological ethic of respect for the Other through current ecological philosophies, such as those developed by Val Plumwood. Thereafter, it contextualises the novels within the broader field of science fiction, and speculative fiction in particular, arguing that the shift from a critical utopian to a critical dystopian style evinces their changing treatment of this ecological ethic within their work. The remainder of the thesis is divided into two parts, each providing close readings of chosen novels in the light of this argument. Part Two provides a reading of Le Guin’s early Hainish novels, The Left Hand of Darkness, The Word for World is Forest and The Dispossessed, followed by an examination of Piercy’s Woman on the Edge of Time, Lessing’s The Marriages Between Zones Three, Four and Five, and Atwood’s The Handmaid’s Tale. The third, and final, part of the thesis consists of individual chapters analysing the later speculative novels of each author. Piercy’s He, She and It, Le Guin’s The Telling, and Atwood’s Oryx and Crake are all scrutinised, as are Lessing’s two recent ‘Ifrik’ novels. This thesis shows, then, that speculative fiction is able to realise through fiction many of the ideals of ecological thinkers. Furthermore, the increasing dystopianism of these novels reflects the greater urgency with which the problem of Othering needs to be addressed in the light of the present global ecological crisis.