Since the 1950s, as economics has responded to new environmental challenges, views on natural resource scarcity have also evolved. Three distinct phases are discernible in this evolution. From the 1950s through the 1970s, the “Resource Depletion Era”, the concern was mainly with the environment as a source of key natural resources and a sink for waste, and thus the focus was on whether there were physical “limits” on the availability of resources as economies expand and populations grow. From the 1970s to the end of the 20th century, the “Environmental Public Goods Era”, attention shifted to the state of environment and processes of environmental degradation, such as climate change, deforestation, watershed degradation, desertification and acid rain, that resulted in loss of global and local environmental public goods and their important non-market values. Since 2000, the “Ecological Scarcity Era” has seen a growing concern with the state of the world’s ecosystems and Earth system processes, and shifted focus back to possible “limits” to economic and population expansion, but now with the emphasis on potential “planetary boundary” constraints on human activity.