Globe-trotting tourists are doing a lot more damage to the planet than previously thought, according to a new study that takes more than just air miles into consideration.

In the report, published in the journal Nature, researchers determined that tourism accounts for around eight percent of global carbon emissions.

This is around three times more than earlier estimates, with the carbon footprint growing four times more quickly than thought between 2009 and 2013, CNN reports.

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The researchers, who describe tourism as "largely a high-income affair," say they looked at emissions produced by the eating, shopping, and local transportation activities of tourists in 160 countries worldwide, as well as the air travel involved.

They also looked at domestic as well as international travel, and say tourists from the U.S. are responsible for the most emissions, followed by those from China, Germany, and India.

Lead researcher Dr. Arunima Malik from the University of Sydney tells the BBC that tourism is responsible for up to 80% of emissions in places like the Maldives and the Seychelles.

"The small island states are in a difficult position because we like traveling to these locations and those small island states very much rely on tourist income but they are also at the same time vulnerable to the effects of rising seas and climate change," says Malik, who warns that at the rate tourism is growing, it is "crucial" to make it sustainable.

This article originally appeared on Newser.