This paper is concerned with how the objective of agricultural sustainability can be incorporated into convention analyses of agricultural development projects. The most straightforward approach is to assume that agricultural sustainability, including the ecological concept of ‘resilience’ is dependent on the constancy of the natural capital stock. Special sustainability criteria need only be invoked in the presence of degradation or depletion; otherwise, economic efficiency can be optimally pursued. The resulting ‘rules’ for project appraisal are demonstrated both theoretically and with the example of a gum arabic rehabilitation project in Sudan.