Gardner and Stern (2002) compile the critical environmental problems that the world is challenging, and reflect that even though it is recognized that those problems are caused by humans, the use of the human
behaviour science is not habitually used to tackle them.
For Stern (2000, p.408) an environmentally significant behaviour (ESB) can be defined by the extent to which it impacts the environment. The ‘Conservation Psychology’ studies the ESBs, having in mind the
physical and social context within which they are made (DMU, 2007a).
The three ESBs that this study presents have been chosen in order to show a range of theories to explain ESBs. In each case, a first sub-section comments the ESB, classifies it and gives factors on which they may be based; and a second part explains different theories’ approaches to explain those ESBs. They all refer personal behaviours. The magnitude of their final environmental impacts will depend on the extent to which the actor’s ESB influences other people’s behaviours.