As more and more people travel, and as they travel to increasingly remote places, a lot of people are asking that question. And many are asking whether tourism itself, which generally involves people from rich countries using the world for their entertainment, is truly sustainable, ethical or just. The answer, in a nutshell, is “Not always – but it can be.”

Travel has enormous impacts on the environment. More than one billion people now cross international borders for tourism every year, according to the United Nations World Tourism Organization, with at least that many traveling domestically. This means billions of people using fossil fuel to travel hundreds or thousands of miles, and once they get to their destination, using water, energy and other resources in volumes much higher than local residents – at times more than they would use at home. Visitors often place severe pressure on natural resources and ecosystems, damage habitats and cultural sites, crowd out residents from popular cities and towns, and change the nature of rural and urban areas alike.

If we look at climate impacts, which are one measure of sustainability, tourism would appear highly suspect. Up to 10 percent of global warming may be caused by air transportation alone. In a 2013 article, The New York Times called air travel our “biggest carbon sin,” while organizations like Plane Stupid are calling for radical reductions in air travel to combat its impact on global warming.

With flights increasing by about 5 percent per year, however, the impact of aviation on our environment is poised to increase. Carbon offset measures have made only a small impact on carbon emissions, and are seen by many critics as mere window dressing. And the worst offenders in terms of climate change, so-called long-haul flights, are on the rise, including to places as distant as Antarctica and the Maldives – places that are going to be most affected by climate change. The next vanguard of recreational travel, space tourism, promises to do even more environmental damage, according to many scientists.

That said, there are marked improvements in many aspects of the aviation industry, as our own Portland International Jetport illustrates. With its LEED Gold-certified terminal expansion that uses locally sourced construction materials, its geothermal heating and cooling system, and its innovative method for capturing and recycling de-icing fluid, the Jetport is among national leaders in managing airport operations more sustainably. And that is the key. Travel itself may have unavoidable impacts on the environment, but it can be done more thoughtfully and sustainably.

Once on the ground, what tourists actually do matters – a lot. An international traveler who arrives in Boston, then rents an RV and travels cross-country with his small family, is going to have much more impact than someone who rents a small car, uses public transit, or stays in one city and gets around through walking or biking. There are now websites where travelers can calculate the carbon footprint of their trip and choose the itinerary, mode of travel and even flights that will have the least impact.

In terms of lodging and meals, staying in a large resort that uses tons of water and other resources to meet the needs of its guests, or to keep golf courses and gardens looking lush in the middle of the desert, is obviously more impactful than staying in a small ecolodge built of local, renewable materials and supported by solar or wind power. Eating local foods is more sustainable than eating foods shipped halfway around the world, which oddly happens even when people stay in tropical resorts, where bananas could grow in their courtyard.

Of course, there are many in-betweens, including hotels and resorts that use sustainable management practices like the Inn by the Sea in Cape Elizabeth. The inn has received considerable recognition for its innovative approach, incorporating reused materials in construction, using solar heating for its saltwater pool, serving sustainable fish species in its restaurant, and making the property more attractive to wildlife, including the endangered New England cottontail rabbit.

One of the benefits to projects like the Inn by the Sea’s habitat restoration is how much they educate and inspire people to protect and care for the natural world. In a class at the University of Southern Maine this past year, Dr. Bruce Rinker of Gorham’s Biodiversity Research Institute taught students about the intimate connection between tourism, wildlife and biodiversity. They learned of tropical forest canopy walks in Central America that teach tourists about this fragile and diverse habitat; about the economic and conservation benefits of birdwatching; and about projects in places from the Arctic to Sri Lanka that use tourist interest and dollars to protect species ranging from polar bears to sea turtles.

If we can promote a sense of stewardship among travelers, encouraging them to protect places and species they fall in love with during their travels, this could be one of the greatest benefits of tourism – call it the “caring offset,” if you will.

One final aspect of sustainable tourism is its connection to local economic development. Many communities see the value in tourist dollars, but don’t want to give up their identity, character and sense of place just to attract visitors. And they don’t have to. In fact, many tourists want to visit places that have managed to preserve essential parts of their history, language, and cultural heritage. They are turning away from manufactured entertainment centers like Orlando, Florida, and Las Vegas to find small, relatively unchanged places where they can experience more authentic local pleasures.

The real question here is not whether tourism is sustainable, but whether it is more sustainable than the alternatives. In many parts of the world, tourism is more appealing than cutting down forests, killing wildlife for sale on the world market, or working in factories. Tourism can create incentives to protect natural places and wildlife. It can also help protect the character of local communities that otherwise might be forced to change in the face of “development.”

Sustainable tourism is complex and sometimes contentious. It is not a panacea by any means, nor is it always readily achievable. But it offers a way to use a powerful part of human nature – our innate desire to travel in order to learn about other places and people – to actually protect and preserve those places. At its best, tourism can even be restorative and transformative, leading to more sustainable and livable communities and to diverse and healthy landscapes. I see this potential as a large part of our state’s future.