Thank you to Glyn Moody for highlighting another example of the tragedy of the commons in his post: Greed vs. Survival: Which Prevails?. At national and EU level, we have a mechanism for avoiding tragedies of the commons. We can pass laws and regulate the commons. For example, in the UK one can't tip mercury into a river without being subject to severe penalties, so pollution of rivers isn't an intractable problem.

The problem comes with tragedies of the global commons (eg. climate change) where there is no democratic government. That's why I'm in favour of a world government. If a world government were to be established we could impose a global carbon tax and so reduce our carbon emissions to an acceptable level.

In Moody's 'Greed vs. Survival: Which Prevails?', the problem is that the benefits of selling the land are at national level, but the costs are at global level. Whenever that's the case, things should be decided at global level, but there's no mechanism for that. Bring on the world government!