One model that can be used to define environmental sustainability is the Planetary Boundaries Model, introduced by Johan Rockström and colleagues in 2009 to describe the limits of the impact of human activities on the Earth. The graphic in the comic panel shows the iconic Planetary Boundaries diagram. Here, red areas indicate "overshoot" of safe operating limits (e.g., biodiversity), and yellow indicates a zone of increasing risk (e.g., climate change and deforestation).

An extended version relates these limits to a social foundation that should be reached as a minimum, resulting in the sustainable doughnut that describes a safe and just space for us humans.