In Philip K Dick’s 1968 novel, Do Androids Dream of Electric Sheep, that forms the basis of the 1982 movie, a nuclear “World War Terminus” was responsible for post-apocalyptic San Francisco.
This is the reason why most animals are dead and humans use bioengineering and cloning to create artificial animals like snakes and robot cats. Radiation and nuclear war is also a motivation for people to move off-world (that and the fact each person who does gets their own replicant butler).
The 1982 movie doesn’t mention nuclear war as far as I can tell, but these plot devices of off-world colonies and artificial animals remain as holder overs. When I watch Blade Runner 2049 tomorrow at theNational Air and Space Museum, Smithsonian Institution IMAX theater, I will keep an eye out for nuclear plot points.