Own One Thing Efforts are efforts that assign to groups or individuals the responsibility to take care of one small area of the local ecosystem. In short, the group acts as if they were owners of that one thing in order to foster the emotional investment to act as stewards for that one thing.
For instance, a community organization or group of friends might adopt a section of a meadow to plant native plants upon which area birds or insects rely or a group might partner to push a local grocery store to charge their customers for the plastic grocery bags.
The efforts can be formal or informal and involve large groups or small ones. The point is only to give people a small, specific and actionable task that makes some real improvement in the health of an ecosystem.
The sense of ownership involved in these efforts also give the locality a force to oppose efforts to exploit or destroy that ecosystem by developers, mining and extraction operations or industrial agriculture companies.