I love apps and I love social justice and environmentalism and I've found a couple apps that put the two together in actually successful ways.
First is my favorite, I use it several times a week. Missing Maps
(iOS and browser, I think Android too but I'm not sure)
Each year, disasters around the world kill nearly 100,000 and affect or displace 200 million people. Many of the places where these disasters occur are literally 'missing' from any map and first responders lack the information to make valuable decisions regarding relief efforts. Missing Maps is an open, collaborative project in which you can help to map areas where humanitarian organisations are trying to meet the needs of vulnerable people.
Doctors Without Boarders is involved so you know it's good. You swipe through a series of satellite images looking for buildings and sometimes roads. This is harder than it seems because some of the buildings are huts that look a lot like trees or bushes on satellite, but with a little practice you learn how to spot them. The Ebola outbreak showed the world's disaster reflief community that there are still areas of the world that are not adequately mapped. You can't deliver medical or disaster relief care to people if you don't know where they live. Missing Maps aims to solve that problem. Freeland's WildScan
(iOS and Android)
WildScan is a comprehensive species identification and response mobile application designed to combat wildlife trafficking. The application is designed to help frontline wildlife law enforcement agencies correctly identify, report and handle marine, freshwater and terrestrial animals caught in the illegal wildlife trade.
This one is less useful in the US given that it's designed to help people identify species in Asian wildlife markets, but if you're involved with the exotic animal pet trade (as I was for many years) you might find it handy. If you live in a country with lax wildlife protection laws or enforcement you might like this as well. It provides an easy way to identify and report protected species. Wildlife trafficking is the fourth largest black market after guns, drugs, and human trafficking, and all those markets are related with traffickers often switching from one to another. Despite this enforcement is often underfunded and a lot of plants and animals slip through the cracks, even in the US. This app makes it easier for non-experts aid law enforcement.
If you have a favorite app for a good cause please post it!