Responsible for 10 percent of the world's gross domestic product, one in 11 jobs globally, and 5 percent of world carbon dioxide emissions, tourism will inevitably have a serious impact on people and the environment.

This year, the United Nations is trying to ensure that impact is a positive one, partnering with companies, nonprofits and countries around the world to sponsor the International Year of Sustainable Tourism for Development.

Vacation "cannot be a pretext either for irresponsibility or for exploitation," Cardinal Peter Turkson, prefect of the Vatican's Dicastery for Promoting for Integral Human Development, said in an Aug. 1 message for World Tourism Day. "In fact, it is a noble time in which everyone can add value to one's own life and that of others."

Turkson added that the Vatican supports the U.N. World Tourism Organization definition of "sustainable tourism": tourism that respects people's heritage, personal dignity and labor rights as well as the natural environment.

While tourism can contribute to problems such as human trafficking and overuse of resources, the Year of Sustainable Tourism attempts to show how these problems can be reversed, making tourism a vehicle for conservation, economic mobility and greater understanding among nations.

U.N. World Tourism Organization materials say tourism can contribute to all 17 of the U.N.'s sustainable development goals, a list of objectives that aim to "end poverty, protect the planet, and ensure prosperity for all" by 2030.

For individual tourists who want to help, the U.N. World Tourism Organization's pamphlet, "Tips for a Responsible Traveler," provides advice such as "choose tourism operators with environmental policies and community projects in place" and "respect human rights and protect children from exploitation."