So how does that figure into all the individual pieces of land that people own? Is my land not part of the larger eco-system of the planet? I'd argue it is, and I take pretty darn good care of it. Are we somehow saying that we can't extrapolate this to a larger scale?

For further reading, you might find this interesting:

http://en.wikipedia.org/wiki/Continuum_fallacy

and

http://en.wikipedia.org/wiki/Sorites_paradox

But if you have land near the ocean, you may sail a few miles and throw it there. Your land is clean - the eco-system is not. Or, say, you have a river, and take most of it's water: your land is better off, then next lands were the river would have flow to not so much, and so on.

Sure could, and I'm guessing the current law framework would semi-allow it. Do you think it would be different if people were allowed to own pieces of ocean/sea?