An impact is considered to be the change in a given state over time, resulting from an external stimulus. It is important to distinguish internal and external stimuli: a change in state from internal drivers, e.g. the maturing of an ecosystem and the successional changes in species (e.g. from grasses to trees) as a result, would not be considered an impact, under that definition. To best understand the impacts of tourism, it is easiest to examine economic, social and environmental impacts as separate categories from each other. The caveat here, is that the boundaries between categories are generally fuzzier in any given tourism context. As we become better at understanding tourism impacts, we will start to see relationships between social, environmental and economic impacts. Becken, S., Garofano, N., McLennan, C.L., Moore, S., Rajan, R. & Watt, M. (2014). From Challenges to Solutions 2nd White Paper on Tourism and Water: Providing the business case. Griffith Institute for Tourism Research Report Series Report No 1 March 2014