Recent interest in the concepts of sustainability and s ustainable development has highlighted the current incompatability of environmental and development thinking - especiall y in the area of productive land management. The focus of the thesis has been to see if there are areas where environmental and development ethics can be brought together under some ' overarching principle' . The areas w ithin development that are specifically covered are basic human needs and rights, Sen's capability theory and the DFID sustainable rural livelihood approach. Chapter 4 focuses in more detail on the practical and legal implications of the Universal Declarations indication of 'The Right to Food'. T he areas covered within environmental ethi cs are Naess's deep ecology, Bookchin' s social ecology, Leopold's Land Ethic and its extension into the area of ecosystem health and integrity. The problems of defining sustainability are examined to see if there is an 'international normative understanding' and a manifestation of this in current international law. As productive land use is a real contact area between concerns for the environment and development, a review of the possible use of agroecology as a framework for practical analysis is undertaken. This is fo llowed by a short case study of the issues raised. A proposal is made to extend Shue's focus on subsistence rights to ensure that all the proposed duties become operative for humans. A move is also made to extend the subsistence rights to include non-humans. The implications of this move in terms of the duty requirements, now and in the future, are examined. In particular, the implications of reaching a 'Square 4' problem, a direct clash between human a nd non-human subsistence rights, is discussed. This clash, if real, will mean that both humans and non-humans are unable to meet their basic needs, and the consequences for humans and non-humans alike of this scenario are bleak. Subsistence rights provide a basis for decision making in programmes to ensure that the 'waves of duty' identified by Waldron are put into practice. For natural resource programmes this approach combines the ecosystem health/integrity rationale with that of human capability theory through the use of an expanded agroecological framework. The su bsistence rights framework, it is argued, should be the foundation on which all institutions, policies and operational programmes are based.