There is growing recognition that "human development" frameworks, such as the Capabilities Approach (CA) with its emphasis on the promotion of justice, offer promise for guiding efforts aimed at enhancing mental wellbeing. This article explores challenges that might arise when there is a need to arbitrate among the competing demands of different parties in their efforts to enhance capabilities. Particular tensions can arise when the efforts of particular individuals to enhance their capabilities exert pressure on scarce resources, or threaten the safety and security of people living in precarious environmental contexts. Consideration is given to the need for "an ethos of restraint" to balance the consumption of resources aimed at facilitating human development on the one hand, with the need to promote environmental justice on the other. The paper highlights research that has investigated how environmental factors can impact on mental wellbeing, including rapid urbanization, climate change related issues (such as weather systems, drought, food insecurity and rising sea-levels), and access to "green/blue spaces". As such, the paper explores the important links that can exist between people and the ecosystems in which they live (including the way in which particular cultural beliefs and practices of indigenous groups can be tethered to the land). Elinor Ostrom's "design principles", derived from her work investigating the sustainable use of pooled resources, are presented as a helpful means of assisting members of communities to negotiate and apply "functioning constraints", which can promote environmental justice whilst not compromising efforts aimed at promoting mental wellbeing.