As the environment is a basic component of the tourism industry's assets, tourism revenues are often used to measure the economic value of protected areas.
Money is earned from tourism through informal employment (e.g. street vendors, informal guides, rickshaw drivers)
The positive side of informal employment is that the money is returned to the local economy, and has a great multiplier effect as it is spent over and over again.
The WTO estimates that tourism generates an indirect contribution equal to 100% of direct tourism expenditures