If the whole world starts looking like Syria then in my opinion the best places to colonise would be factory farms. They have tons of food (in the very literal sense), water supplies, power supplies, huge buildings to live in, everything you could possibly need to accommodate large numbers of humans. And of course they wouldn't be there if they weren't hideously subsidized by the tax payer, so basically you would just be taking back something you already own anyway.
We have massive homeless problems, massive unemployment problems, international starvation is on the rise, I cannot think of any other way these problems can be all solved at once other than by directing our attentions on the very thing causing them all. Which is a blindingly obvious thing to say but you know the problems of talking to the general public about this.
But if people want to prevent civil wars and wars generally then this clearly has to be done.
PICKING OUT A SINGLE TARGET
A hopefully bloodless way of doing this would be pick out a single target and expose how much the farm consumes in terms of resources and expose the animal cruelty and environmental destruction they indulge in. Tell the general public where the farm is so they can visit it. I feel in the U.K. a place in the southwest would be best as it tends to be more vegan friendly than than most of the rest of the U.K. Bristol (the southwest's biggest metropolis) is home to Viva! (Vegetarians International Voice For Animals) who recorded under cover footage at a pig farm in the U.K. where piglets were being illegally mutilated. Surprisingly this received favourable coverage in the right wing British tabloid The Daily Mail which is usually condemning animal rights activists. You can read it here. As you might expect there are many comments beneath the article condemning the behaviour of the farmers. They can't all be from vegans. Yet we know it seems just too difficult/inconvenient for them to openly acknowledge that their buying habits are the cause of this cruelty. I think only by getting people physically close to the cruelty is it ever going to end. But at the same time with this approach people can realise that it's this cruelty that is responsible for virtually all the economic turmoil in the world.