A summertime jaunt to Croatia or a destination wedding in Greece might stimulate the local economies. But according to a new study published today in Nature Climate Change*, all that jet-setting deals a big blow to the environment.

The trillion-dollar global tourism industry has a significant carbon footprint, which is the amount of carbon dioxide and other greenhouse gases emitted through burning fossil fuels, a major driver of climate change. In total, the Nature study, which measured carbon flows connected to tourism in 160 countries, found that all of those luxurious holidays on the other side of the globe account for nearly 8 percent of the world’s greenhouse gas emissions. That’s three percent higher than previous estimates.

The team of researchers from The University of Sydney in Australia and University of Queensland in Brisbane focused their calculations on both how much carbon a tourist and a host destination accumulates. Long distance air travel was the largest contributor to the footprint, accounting for 12 percent of the total footprint. But that doesn’t tell the full story. The team’s estimate also includes how much greenhouse gas was emitted in order to supply food, power resorts, ship products, travel to hotspots, and build or repair infrastructure.

Global tourism’s biggest carbon culprit was the United States. The US produced almost twice as many greenhouse gas emissions as both a travel destination and as tourists abroad than runner-up China. Travel across the borders of Canada and Mexico into the United States made up 2.7 percent of the total global footprint.

Arunima Malik, a sustainability assessment researcher at the University of Sydney and one of the study’s authors, said the team found that there is a positive relationship between affluence and emissions. Once income levels rose above $40,000, a 10 percent increase in wealth from there on would lead to a nearly 13 percent increase of the carbon footprint.

Global tourism’s biggest carbon culprit was the United States

“We are heading toward higher and higher levels of affluence and that basically means a higher and higher portion of disposable income is spent on traveling,” said Jukka Heinonen, who studies sustainably built environments at the University of Iceland, Reykjavik, and did not participate in the study.

The study further illustrates that from 2009 to 2013, carbon emissions from tourism rose four times more than previously expected.

That’s not entirely surprising, seeing as places like Japan, Hungary and Nepal, set goals to double their tourism game in recent years. “Mitigation efforts haven't worked because the carbon footprint increases strongly with an increase in affluence and decreases weakly with improvements in technology,” Malik noted.

What’s more is that many of these destinations, especially islands, will face climate change’s most devastating effects, which will only be exacerbated by the carbon output of tourist activities that bring in their main source of income. In other words, these places shoulder the burden of a higher carbon footprint even after the tourists are gone because they provide the supply chain of goods and services.

Some places looking to attract the vacation crowd are working to combat their growing carbon footprint. Montenegro, a small nation ashore the Adriatic Sea, started its carbon neutral initiative in 2013 and the project was slated for completion last month. The country aimed to increase public transit around Kotor Bay (in order to decrease traffic jams) and invest in energy efficient infrastructure or use renewable energy to power its tourism facilities.

Tourism in Montenegro, which is home to 622,000 people, accounts for a third of its gross domestic product; the tiny country’s greenhouse gas emissions are predicted to rise 40 percent higher than the 1990 baseline by 2020. But people from popular vacation spots like Croatia, Montenegro’s neighbor to the west, exert smaller footprints on other countries when they travel than visitors do in their home country.

Similarly, Maya Bay in Thailand—made famous in The Beach (2000), starring Leonardo DiCaprio—is only open seasonally starting this June to allow coral reefs and sea life to recuperate while beach cleanups take place, the Associated Press reports. The location, where where tons of partiers come for full moon celebrations, is already feeling the effects of climate change, which will worsen with increasing greenhouse gas emissions from the booming global tourism industry.

Increasing ocean temperatures causes coral bleaching, which happens when coral expels algae from its tissues, causing it to lose color and burden the ecosystem. Add stressors like boat traffic and divers and recovery slows dramatically. Maya Bay typically attracts 200 boats and 4,000 guests a day. Travel to Thailand has nearly tripled in the last two decades. The country attracted 35 million guests last year.

However, because of the steep increase in the global footprint in just four years, previous efforts to remedy the negative environmental impacts of tourism were virtually rendered moot, the team found. As Freya Higgins Desbiolles, a tourism and social justice researcher at the University of South Australia in Adelaide, points out, the study essentially negates industry claims that they’re being “more responsible and sustainable.”

“The fact is the global elite enjoys numerous long-haul trips that are in fact not sustainable,” said Higgins Desbiolles, who was not involved in this study.

So what can we do? Stay home? Perhaps. Even though food and fuel would obviously still be consumed at home, tourists’ tendency to splurge made the scales tip toward a growing footprint once again, according to the study.

But that’s not really a likely option. According to the United Nations World Tourism Organization, global tourism accounts for approximately 10 percent of the world’s GDP and one in 10 jobs. Furthermore, the Paris Climate Accord excludes aviation and bunker shipping—which together make up 12 percent of tourism’s carbon footprint—from its targets.

That’s only relevant if a country is in favor of the deal. The largest contributor to tourism’s carbon footprint, the US, announced plans to back out of the agreement in June 2017 making it the only nation that now disapproves of the plan.

Malik considers the team’s findings “eye-opening.” She hopes this helps in starting a dialogue at multiple levels—from individuals, organizations and policy-makers—to collectively work together to address emissions from tourism.

After all, as Heinonen said, “If the number of trips and distances keep increasing then it might be that technology doesn’t catch up.”