As well as personal, communitarian, and humanitarian reasons for living simply, there are, of course, also environmental reasons. It has long been recognized that consumption and ecological impact are correlated, and from this correlation it follows that reducing consumption can be an effective means for reducing ecological impact. Indeed, it is becoming increasingly clear that simpler living, in the sense of reduced and more efficient consumption, is needed to save our planet from grave ecological harm. This is especially so in the affluent societies, where lifestyles of reduced consumption will be a necessary part of any transition to a sustainable future.
This has been acknowledged in several of the leading international policy documents on the environment which have emerged in recent decades. Agenda 21, for example – the main policy document to emerge from the Rio Earth Summit in 1992 – argued that ‘the major cause of the continued deterioration of the global environment is the unsustainable pattern of consumption and production, particularly in the industrialized countries.’ This document called for the following actions:
- To promote patterns of consumption and production that reduce environmental stress and will meet the basic needs of humanity.
- To develop a better understanding of the role of consumption and how to bring about more sustainable consumption patterns.
In more recent years, this message has been widely affirmed. When the World Summit convened in Johannesburg in 2002, ‘changing consumption and production patterns’ was identified as one of three ‘overarching objectives’ for sustainable development. What these and other reports imply is that fundamental lifestyle changes with respect to private consumption are one of the main preconditions to ecological sustainability.
 See generally, Paul Ehrlich and Anne Ehrlich, The Population Explosion (1990) (discussing the ‘I = PAT’ identity, which holds that environmental impact (I) is a product of population (P), affluence (A), and technology (T)).
 To clarify, what is needed in terms of consumption is not just ‘less of the same,’ but ‘less, different, and more efficient.’
 But see, Hana Librova, ‘The Environmentally Friendly Lifestyle: Simple or Complicated? ‘ (2008) 44(6) Czech Sociological Review 1111 (arguing that there is nothing very ‘simple,’ in the sense of ‘easy,’ about living sustainably in consumer cultures).
 See United Nations Department of Economic and Social Affairs, ‘Agenda 21,’ Sect. 4.3, <http://www.un.org/esa/dsd/agenda21/> at 10 October 2010.
 Ibid, Sect. 4.7.
 United Nations, ‘World Summit on Sustainable Development’ (2002) <http://www.un-documents.net/jburgdec.htm> at 10 November 2010.
 There is also a growing recognition that ecological and humanitarian issues are closely linked. See Millennium Ecosystem Assessment, Ecosystems and Human Well-Being (2005) 2 (acknowledging that ‘the degradation of ecosystems services is already a significant barrier to achieving the Millennium Development Goals’).