As online challenges go, #trashtag, which went viral on social media over the weekend, is a pretty wholesome one. Hundreds of people shared photos of themselves litter-picking in trash-strewn parks and streets on Saturday and Sunday, while calling on others to start cleaning up their communities.

The idea for #trashtag has been around for several years, with one company promoting the idea back in 2015 as a way to protect threatened wilderness areas.

But it gathered steam over the weekend, as users on Instagram, Reddit and Twitter shared dramatically different before and after photos of one wooded area where a man bagged up hundreds of plastic objects — accompanied with an invitation to find a place “that needs some cleaning or maintenance” and “take a photo when you have done something about it.”

The idea soon spread, with some social media users incorporating “trashtag” into their weekend trips.

Others cleaned up in their local communities.

Many added a message explaining why movements like #trashtag are needed to protect natural landscapes.

Write to Ciara Nugent at ciara.nugent@time.com.