Pretty much all the challenges we're facing with regard to the environment and natural resources, are collective action problems...
...Whether it's global warming, water shortages, decrease in biodiversity, phosphorus depletion, etc.: Collective Action Problems (or more specifically, Tragedy of the Commons problems - see the video below).
Traditionally, regulation and privatization are the two main ways to mitigate these problems. But they don't seem to be all that successful, for a variety of reasons. Time for another solution: Crowdacting. Here are some examples of what can be done by us regular folks. Please feel free to add ideas to the list in the comment box!
Project ideas (feel free to add!)