This thesis examines the question of living nature and its bearing on ecological thought in the light or the philosophy of Martin Heidegger. The difficulty of adequately thinking about living nature in the terms developed in Being and Time (1927) is taken as the starting point for the investigation. The thesis concentrates on Heidegger's thought in the period beginning with the 1929/30 lectures The Fundamental Concepts of Metaphysics: World, Finitude, Solitude and ending with the courses on Heraclitus in 1943 and (...) 1944. In this 'middle period' Heidegger' attempts to fonnulate a phenomenology of animal life and then a thinking of the place of living nature in the 'history of being' which does not return to the vitalist principles with which he had previously broken. The thesis considers the extent to which these attempts to find another way to think about living nature are successful. To this end a variety of lecture and seminar courses together with manuscripts from this period are discussed, some of which have only recently become available, including the seminars on Nietzsche's second Untimely Meditation and Herder's Treatise on the Origin ofLanguage and the manuscripts Besinnung and Die Geschichte des Seyns. Contemporary responses to Heidegger's thinking of living nature and its relevance for philosophical ecology, including those of Jacques Derrida, Michel Haar, Giorgio Agamben and Michael Zimmennan are re-evaluated on this basis. -. :'. j,-- The guiding concept of the investigation is the notion of poverty, which plays a variety of roles in the context under discussion. In particular, the thesis presented in The Fundamental Concept of Metaphysics that the animal is 'poor in world', has been seriously misunderstood by many commentators. If the poverty in question is properly understood as a thesiS concerning the fundamental attunement of the encounter between Dasein and living nature, then we can see how this concept of poverty develops in various directions in the following years, informing Heidegger's understanding of the capabilities of living beings, of the 'earth', the silence of language and finally allows for the development of a thinking of freedom that is proper to the earth itself, rather than a development beyond the earthly. It is argued that the notion of poverty is an essential counter to a prevalent Spinozist and Nietzschean strain in ecological thought that thinks living nature on the basis of plenum or overflow and concedes no space for a true freedom of the earth. (shrink)