i assume this is for a class project. if it is check out the cruse line industry. they are absolutely horrible/super fun. millions of gallons of fuel, tons and tons of trash, and they have a terrible record on cleaning up after themselves, although its gotten better in the past few years. I dont remember what line it was specifically but they have been know to dump extremely hazardous waist illegally while at sea.
i took a summer class on the industry last year, 7 credits for 3 weeks of class followed by a week on the ship. it was dope. if this is something your interested in i might be able to find some notes and maybe a powerpoint, but no promises.
I live in Duluth, MN, and here the biggest negative impact the tourists have on the environment is feeding the goddamn fucking seagulls. Back when Duluth used to be a legit seaport rather than a tourist attraction, the seagulls actually had to work to get food. Because of this, the seagull population was held in check. Now, the tourists feed the rats with wings bread crumbs, popcorn, and pretty much anything the rats with wings will eat (which is, coincidentally, anything). They've even begun to get aggressive. If you turn your back for a second while eating outside, your food is GONE. And they beg, too. So now we have an overpopulation of B-POO bombers circling the sky, just waiting to drop their shit missiles on your car, your head, your bike, or any other surface you recently cleaned.