For decades, travel has been framed as an unequivocal good: broadening perspectives, supporting local economies, and connecting cultures. And much of that is still true.

But in recent years, another reality has become harder to ignore. In some of the world’s most beloved destinations, the sheer volume of visitors is beginning to strain the very places people come to experience.

If you’re planning a trip to Spain or elsewhere in Europe this summer, you may come across more than just beautiful architecture and charming cafes—you might also see signs of growing frustration among locals. In cities across Spain, Portugal, Italy, and beyond, residents have taken to the streets to protest what’s being called “overtourism.” The signs say things like “Tourists go home” and “This isn’t Disneyland.” But what’s behind these protests, and what can you do as a traveler to be part of the solution, not the problem?