Apple's 'Apps for Earth' promo directs select app revenues to World Wildlife Fund

The promotion specifically covers 27 apps through April 24. The apps aren't necessarily environmentally-themed — some examples include the games Angry Birds 2 and Hearthstone, the photo-editing tool Enlight, and the popular messaging app Line.

Although visiting an app's product page will show information about the promotion, an Apps for Earth banner is only visible on the iPhone version of the App Store, not the iPad or iTunes.

The promotion is in recognition of Earth Day on April 22, and Apple's increasing work to portray itself as an environmentally-friendly company, despite the resources consumed to make and sell its products, and pollution problems in its supply chain.

"We have been putting quite an emphasis these past few years on environmental initiatives at Apple, really trying to walk the walk with respect to our own operations and how we make and recycle our products," Apple's VP of environment, policy and social initiatives, Lisa Jackson, told Reuters. "This is about engaging our customers in our work."

The company is for instance trying to make its global operations entirely supported by clean, renewable energy, and offset the impact of its supply chain through projects like solar farms and protecting forests. In March, Apple revealed a robot dubbed "Liam," designed to recycle as much as possible from old devices.