For decades, travel has been a major part of life in Oz. After college, young Aussies take a year off to wait tables in London or backpack through South America. Stop at any youth hostel in Europe and you're bound to find at least one person from Down Under. Retirees flush with retirement cash hop a plane to visit the children and grandchildren spread out around the world. Executives and entrepreneurs travel frequently to stay connected in an interconnected global economy. No wonder some of the best guidebooks in the world -- the Lonely Planet series -- are cranked out in Melbourne.

Horin says it all has to stop. Every time an Australian boards one of those big Qantas 747s (she calls them "toxic flying machines"), she argues, they're doing enormous damage to the environment. She estimates that a round trip from Sydney to London emits the equivalent of nine tons of CO2 per passengers, twice as much as each person on the planet generates annually through eating, driving, and heating or cooling their homes. Yikes.

But does she, or anyone else, have the right to lecture Australians about their travel habits? It's not that easy, Adele.

First off, Australia is not only an island, it's an island in the middle of nowhere. London is 10,000 miles away from Sydney. Tokyo and Shanghai are 5,000 miles away. Singapore, an important financial hub for Australia, is 4,000 miles away. And the country is not exactly a Martha's Vineyard-size island -- a coast to coast drive, much of it through the desert, takes days.

All that air travel accounts for just 1 percent of Australia's total greenhouse gas emissions. Compare that to 1.5 percent worldwide and 3.5 percent in the U.S. and you wonder if Aussies are doing that much damage. And flying is still less polluting, overall, than driving - 10 percent of Australia's GHG emissions come from cars; that figure is 14 percent worldwide.

Australians are some of the most environmentally conscious people I've met (not surprising, considering that the Great Barrier Reef is dying and part of the country is suffering through a massive drought), but Horin suggests their propensity for travel make them hypocrites.

In much of the world, cities, forests, beaches and mountains can be reached by train or car. Is it fair to punish Australians because they don't have this luxury? Yes, emissions are a huge concern, and if travel-junkie Australians are contributing disproportionately, then this needs to be taken into account. But is it fair to ask residents of an isolated island nation to suck it up while the rest of us travel freely?

Post updated 11:30 a.m. PDT.

Photo by Qantas.