Family vs World Tribe

Taking care of your family and taking care of ‘the world’ are two enormous extremes, but are 100% related. Every choice we make is the result of a chain reaction and the start of a new chain reaction. We are the turningpoint, though choosing different is not as easy as it might sound.
What is the community/tribe needed to ‘survive sustainably’? How do we and can we take care of eachother when we need to do ‘the same with less’? How many people need to be connected together to take care of eachother effectively? A tree has an ecosystem surrounding it, a human also. What is our tree structure? Can we be a ‘real farmville’ taking care of eachothers prosperity? What is needed for that?