This study argues that environmental scarcity is more likely to result in civil conflict in countries that experience ‘ethnic’ population pressures (i.e. where the size of the largest minority group is close to parity with the majority group). I refer to this argument as the ‘parity-threat’ approach to the study of scarcity-induced domestic conflict. I empirically test my argument by analysing time-series cross-section data for the period 1979–2000 using four alternative environmental indicators: (1) ecological footprint, (2) biocapacity, (3) scarcity of ecological reserves and (4) water scarcity. The results demonstrate that environmental scarcity increases the probability of civil conflict when conditioned by ‘ethnic’ population pressures.