Representing qualitative ecological knowledge is of great interest for ecological modelling. QR provides means to build conceptual models and to make qualitative knowledge explicit, organized and manageable by means of symbolic computing. This chapter discusses the main characteristics of QR using well-known examples. It also shows how this technology can be used to represent ecological knowledge and an overview is given of ecological applications that have already been developed using QR. Ongoing QR research focuses on improving QR tools and technology. An additional goal is to integrate quantitative knowledge with qualitative knowledge. In a collaborative work with ecologists, particularly in the construction of reusable knowledge libraries, it is possible to foresee a wider range of applications to ecological modelling and better ways of dealing with the complexity of ecological and environmental systems. But most of all, the deployment of QR technology for ecological purposes should become an important goal in itself because, as pointed out by (Rykiel 1989), “many questions of interest in ecology can be answered in terms of ‘better or worse’, ‘more or less’, ‘sooner or later’, etc.” and when quantitative methods are inadequate or lacking, it is still possible to make estimates, predictions, and decisions with scientific support.