There is an ongoing discussion in HCI on the need for new theories, methods and techniques to assist researchers and practitioners in both the design of better digital artifacts and effective evaluation of them. As part of this discussion we observe a recent trend where researchers from the IT domain present various definitions of ecologies, approaching the question, “What is a digital ecology? ” from various perspectives. This paper reviews existing definitions, comparing their strengthens and weaknesses and presents a unified definition of digital ecologies, through a theoretical discussion based on systems thinking. It is our ambition that this paper will inspire deeper consideration on what constitutes a digital ecology and how this view of technology affects existing design and evaluation methods and techniques.