Sustainable Tourism World has a specific opinion about what can be considered sustainable. Most of the time, it is related to the role of  REDUCE, REUSE, RECYCLE. Sustainable tourism is an approach to tourism, a way to organise and design it, not a kind of tourism such as active, slow or golf tourism.

These are just a few examples of what STouW consider the best!

– Accommodation, not new buildings but restoration of previous ones, the rule less impact, better is always working well;
– Itineraries deeply related to local culture and the economy of the local population;
– Itineraries made without impact on the earth, so preferred transport would be walking or bicycles, after those public transport: trains, coaches and ferries (eco ran would be much appreciated);
– Services run by local people but with particular attention on the environmental impacts, for instance, restaurants owned and managed by the local community that serves local and organic food (not imported from other countries), second-hand bookshops, recycled clothes and furniture shops.
– Volunteer programs and projects related to not-for-profit associations, groups, or organisations focused on a particular objective.

Sustainable tourism, defined by UNWTO, is described as the kind that fully considers its current and future economic, social and environmental impacts, addressing the needs of visitors, the industry, the environment and host communities.

Sustainable tourism defined by UNWTO should:
1) Make optimal use of environmental resources that constitute a crucial element in tourism development, maintaining essential ecological processes and helping to conserve natural heritage and biodiversity.

2) Respect the socio-cultural authenticity of host communities, conserve their built and living cultural heritage and traditional values, and contribute to intercultural understanding and tolerance.

3) Ensure viable, long-term economic operations, providing socio-economic benefits to all fairly distributed stakeholders, including stable employment and income-earning opportunities and social services to host communities and contributing to poverty alleviation.

Sustainable tourism development requires the informed participation of all relevant stakeholders and strong political leadership to ensure broad participation and consensus building. Furthermore, achieving sustainable tourism is a continuous process, and it requires constant monitoring of impacts and introducing the necessary preventive and corrective measures whenever necessary.

Sustainable tourism should also maintain a high level of tourist satisfaction and ensure a meaningful experience for the tourists, raising their awareness about sustainability issues and promoting sustainable tourism practices among them.

Reference:
Making Tourism More Sustainable – A Guide for Policy Makers, UNEP and UNWTO, 2005, p.11-12