What you're proposing isn't possible without totalitarianism, if I'm reading the extent of what you mean by radical changes within three years.
We'd be talking about physically relocating millions of people into denser communities (camps?), seizing private land, seizing private property, etc.
No democratic nation's people is going to stand for that! It would require a rather brutal authoritarian consolidation of power, which is a more honest way of saying 'strict enforcement'.
As environmentalists are not the types to crack skulls to advance policy, I just don't see your recommendations ever having a chance of working.
There will be trouble on this planet, and to some degree there's not a damn thing anyone can do about it. We're prolific breeders, we're very clever, and we've almost continually found new ways to overcome our limitations and the hurdles nature throws at us.
That's of course why we're in trouble now on a global scale- we've conquered a lot of the things that used to keep population and environmental degradation in check; diseases, malnutrition, low-level warfare, etc.
One thing that's remained unassailable is the fact that you cannot put a Genie back once you've let it out of the bottle. And Genies are notoriously difficult to control once released. We are like teenagers, us human beings, we possess more power than we have the wisdom to control. And like teenagers, we'll likely put ourselves thru some serious bruises learning how to mature.
Disasters are nothing new. There will be disasters. What must be avoided is the perpetration of a worse disaster in the attempts to prevent another one.
I'm not trying to equate your position with his, but George Bush rushed into war with little planning and made a bad situation worse... a three year emergency plan to restructure the entire western world would likely create more problems than it solved and hasten violence and suffering.
Listen, it's totally OK we have different positions on this, since anything of such a magnitude deserves a thorough airing of all sides before action is agreed upon and taken. We're on the same side, just with different ideas about how to succeed in getting to that common goal.