Surely the problem here is one of policy and political will. In terms of cost I can't imagine that the damage done by unplanned firestorms leveling cities is less than retrofitting or controlled burns.
It is never really that simple. Here is a thought experiment:
How does the idea of defensible space work if your neighbor's walls are 5 feet from your walls? What happens when an entire neighborhood is that closely spaced? How do you retrofit the space between buildings?
There are dozens of challenges like the above, and a lot of them delve into personal freedoms. Should you be able to choose what trees to plant on your property? Should you be allowed a shed? Should the government use air surveillance to enforce the cleanliness of your backyard?
There's lots we can do, lots we should do, but it is far from a simple path with a singular solution.
Townhouses with no intervening space would likely be an improvement. Browse Altadena in streetview and you'll see loads of houses with vegetation -- tinder -- stacked between them. Getting rid of those intervening spaces entirely would reduce the surface area exposed to embers while simultaneously depriving homeowners the temptation to store fuel in unwise places.
It totally depends on the type of vegetation. Some species, at least while alive, retain water and resist burning, acting as natural fire stops. Other species, including many imported to the area for aesthetic purposes, act as dry tinder.
How does the idea of defensible space work if your neighbor's walls are 5 feet from your walls? What happens when an entire neighborhood is that closely spaced? How do you retrofit the space between buildings?
There are dozens of challenges like the above, and a lot of them delve into personal freedoms. Should you be able to choose what trees to plant on your property? Should you be allowed a shed? Should the government use air surveillance to enforce the cleanliness of your backyard?
There's lots we can do, lots we should do, but it is far from a simple path with a singular solution.