Enjoyed the chance to talk to the interesting folks at MobiUK on mobile computing and sustainability. I attempted to reconsider the role of ‘resource efficiency’ not as a driver of growth of ICT’s impacts on the planet, but rather to work within planetary limits. Digital technology unquestionably transforms our understanding of the world and helps society reconfigure itself to do new things from better healthcare, climate science, self-driving cars and smart cities, and more. Yet, I argued, ICT has significant direct impacts on energy material systems, and an exponentially growing footprint. As researchers, innovators and practitioners, what should the MobiUK community be doing to help bring about a more environmentally sustainable future? The slides are available.