Land as a planetary boundary: a socioecological perspective

Land is indispensable for crucial socioeconomic functions, including food and energy supply or infrastructure, as well as for biodiversity, carbon sequestration and many other vital ecosystem services. Even though the global land area is well known, the role of land as a planetary boundary is difficult to grasp. This chapter discusses how a focus on net primary production – for example, the production of biomass by green plants through photosynthesis – can help to better understand possible limitations resulting from the finiteness of productive land. Based on data and modelling related to the human appropriation of net primary production we demonstrate how human societies have managed to raise supply of land-based products by (1) taking more from ecosystems and (2) raising efficiency in converting plant growth into products and services. The chapter concludes that planetary boundaries related to the net primary production may be expanded by investing more work, energy, or human ingenuity, but doing so is not without limitations and usually involves trade-offs and costs such as higher environmental impacts that may increase the risk of transgressing other boundaries such as those of nitrogen, phosphorous, water or biodiversity.