Hmmmm.
That map is only semi-useful.
The big strategic level nukes would be targeted on the upwind sides of vast tracts of arable land. You would die in those just as easily as the smaller bombs that would hit cities.
In no scenario gamed at the height of the Cold War that I ever heard of does the opposition force nuke “upwind of arable land”. Add to that the fact that bomb fallout isotopes are pretty short lived in the half life department and you have a pretty low risk for dirt being a strategic target or it being impacted to an extent that it is unable to grow foodstuffs.
Now, a case could be made that there is a strategic potential to carpet a decent sized downwind area with radioactive sodium by detonating a large enhanced radiation weapon (”neutron bomb”) offshore in seawater just to kill people but that bomb would have to be unwieldly large and the sodium isotope would decay fairly quickly.