A network of Enlightenment-era intellectuals debated processes still with us, such as industrialization. The endurance of their ideas reflects their status as mostly privileged white European men. They debated the big questions. Some saw socio-environmental relationships as subject to natural laws. Malthus and Liangji argued that human populations will outstrip food supplies, Ricardo that population growth will increase land rents, and Jevons that efficiency will increase natural resource use. Marx favored historical explanations, considering food poverty and soil degradation to be alterable and functions of linked social and environmental systems. Romanticism vied with materialism. Von Humboldt glorified nature as being in harmony which humans could disrupt. His voyages inspired Darwin, who viewed nature as instead emerging from Malthusian logic, with organisms evolving in conflict over resources. Though inspired by Humboldt, Marsh rejected a view of nature as all-powerful given the environmental destruction he documented. Ultimately, these authors debated whether a better world is possible, a topic still timely as climate change, extinction, and disease threaten us.

A distinct branch of socio-environmental research, grounded in the physical principles of conservation of mass and energy, applies a systems modeling approach to society–environment interactions, emphasizing material and energy flows. Technology and technological advancement, alongside population and resources, feature prominently in determining the metabolisms linking society and nature. This approach mostly focuses on analyzing industrial systems (e.g. Ayers and Kneese, Meadows et al., Beck, Graedel et al.) but also offers insight on agrarian societies (Boserup) and hunter-gatherer communities (Fischer–Kowalski). Across these levels of social organization, technology is variously viewed as overcoming the limits nature places on society, as facilitating the resource exploitation and production of waste that lead to social collapse, or as the basis for internalizing externalities and building a circular economy. Key readings constituting this branch of socio-environmental research draw on tools from economics and engineering, such as input–output models, system models, feedback loops, environmental impact analysis, and material and energy flow accounting.

Ethical quandaries – such as justice and equity for under-represented communities, treatment of animals in laboratory and field research, and editing the genomes of plants, animals, and humans – are becoming ever more insistent in socio-environmental research. Accordingly, socio-environmental research requires that natural and social scientists become conversant with the humanities and that humanists actively engage, in accessible terms, the conceptual and ethical concerns arising in the sciences. Research methods in the humanities differ – where scholars begin with a thesis instead of a hypothesis – from those in the natural and social sciences. While the methodological differences between research in the humanities and the sciences render interdisciplinary cooperation and even communication between these two broad types of inquiry difficult, this section draws attention to the important contributions that ethical, religous, and historical approaches have made to understanding the reciprocal relationships between society and environment. These contributions range from scholars such as Aldo Leopold, Lynn White, and William Cronon to Vandana Shiva, Leonardo Boff, and Gregory Cajete.