As is tradition with Activity Challenges, once you complete this feat on Earth Day then Apple will grant you a new achievement badge within the Activity app on iPhone, as well as various iMessage stickers that you can use to decorate your messages to friends and family members. 2018 marks the second year Apple has launched an Earth Day-specific Activity Challenge, and its goal is the same as it was in 2017.
Apple will be celebrating Earth Day a variety of ways this upcoming week, with employees in retail stores again wearing green shirts instead of traditional navy blue as a way to mark the annual environmental-focused event. In the past, Apple has marked Earth Day by adding a green leaf accent to the Apple logos of its retail stores, and shared Earth Day videos, Apple Music playlists, and featured apps in the App Store.
For Activity Challenges, this is the fourth one in 2018, following a Ring In The New Year Challenge in January, Heart Month Challenge in February, and International Women's Day Challenge in March. If Apple keeps following its annual Activity Challenge schedule, the next physical trial for Apple Watch owners will take place around Mother's Day in May.