Current development processes in many oases across the world are seen as "unsustainable", with reference to water use, pollution or soil depletion, erosion and salinization. While broadly sharing this diagnostic, this paper argues for a more nuanced understanding of environmental processes and landscapes in oases. Specifically, we show that contemporary understanding of oasian environments is often replete with colonial tropes. By drawing on ancient geographical literature, we exemplify such an "oasian model" of environmental explanation in the case of Kharga (Egypt) and contrast it with the results of recent geoarchaeological research conducted in the oasis, which testify to the constitutive instability of oasian spaces.