> Property ownership is a form of democracy that is necessary in human societies.

I smell applause lights. Property ownership and democracy are entirely different concepts.

Also, the things you mention, while being true on Earth, aren't necessarily true in Space (at the moment). Pollution isn't an issue except possibly in Earth's orbit. "Protecting the environment" is another way of saying "keeping the environment friendly to humans". There is no human friendly environment in Space to protect (within our reach). I'm all for land ownership on Moon or Mars but we should probably have this discussion in a few decades when some people actually live there permanently (at which point they will most likely form their own independent government anyways).