First step, in the US at least, stop spending the money required to drive the sprawl. For example, rolling over the dollar value of developments should be on a hectare by hectare basis above a certain value of development (say, $5m). Then instead of looking to roll over gains into every larger plots of low value land, developers that want to get the tax break have to find ways to persistently increase the underlying value per hectare of the property they are developing ... and doing that requires finding was to concentrate and cluster development.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.