We examine the relationship between socioeconomic equity in opportunity and sustainability, as reflected in patterns of food production and fertility. Our analysis spans various levels of social organization, from within the household (gender- and age-related equity) to relations among households (of different material wealth), among regions (particularly rural vs. urban), and among nations (rich and poor). Our preliminary results in this complex area suggest that increasing equality of opportunity at each of these levels can help to increase food production and to lower fertility rates, through varied mechanisms. Working toward such equity constitutes a ''no regrets'' strategy for transitioning to a sustainable society and increasing Earth's carrying capacity for human beings, as measures to reduce the growing disparity between rich and poor have merit on ethical grounds alone. An important caveat, however, is that equity in consumer lifestyles within and between nations cannot be achieved globally by leveling up to consumption from the bottom, Runaway consumption in rich countries must be curbed as part of an effort to reduce the scale of human enterprise to below carrying capacity while still permitting needed development among the poor.
