Because of its dependency on air transport, mitigating tourism greenhouse gas (GHG) emissions might become the most important challenge for the sustainability of the sector. Moreover climate change mitigation will be more and more in conflict with other sustainability objectives such as poverty alleviation and biodiversity conservation through tourism. Indeed, tourism increasingly contributes to global GHG emissions. Transport, and in particular air transport, have the largest share in those emissions, with respectively 75 per cent and 40 per cent of the tourism 5 per cent share of global carbon dioxide (CO2) emissions estimated for 2005 (UNWTO et al. 2008). In terms of the actual contribution to climate change, measured in radiative forcing, the share of air transport is between 54 per cent and 83 per cent of tourism, depending on assumptions made on non-CO2 effects of aviation (Scott et al. 2010). Projections show a strong growth, with more than a doubling by 2035 (UNWTO et al. 2008). In a context where climate policies try to maintain global warming within the limit of +2 °C, this current tourism growth is apparently at odds with global emission reduction targets (Bows, Anderson and Peeters, 2007; Gössling et al. 2010).