Your favorite Pokémon hunting grounds could get a little cleaner this month, thanks to an upcoming Earth Day event. The Pokémon GO mobile game and Mission Blue are organizing worldwide clean-up events.

Participating trainers also will get a reward for their efforts. If 1,500 attendees show up the game will unlock 2x catch Stardust for Grass-, Water-, and Ground-type Pokémon for 48 hours. The bonus will jump to 3x if 3,000 attendees take part in the efforts.

So far, there are 37 clean-up events scheduled for April 22 in 12 different countries. U.S. events are scheduled in San Francisco, North Carolina, and Hawaii so far with more slated to be added by April 18. Interested players must register to one of the existing events or they can share their interest to get an event added near them.

Japan has two events so far, one in Yoyogi Park, Tokyo and another in Kugenuma Kaigan, Kanagawa.

Pokémon GO has previously turned real world areas into limited Safari Zones with huge turnouts. A total of 87,000 people climbed the dunes in Tottori for just such an event.

The Pokémon GO app launched in select countries including the United States in July 2016, and has since launched in more than 50 countries.