a movie from the 1970’s that depicts what’s coming
The movie is set in England in (then) contemporary times. In it something begins to kill grasses. The thing is, since the advent of farming, grasses (wheat, rice, corn, barley, and millet) have been the most important part of the human diet. They underlie civilization: the existence of cities. Large-scale farming of grasses is what makes the existence of cities possible.
So in the movie there is no longer enough food to feed the people living in the cities. They flee into the countryside. Nothing humorous, much less any hilarity ensues. In one scene in particular, any sense of anything remotely titillating about rape is totally disabused.
I can’t remember what exactly started killing grasses in the movie, whether it was mold or a fungus or a germ of some kind. As it happens, a warmer climate makes that premise more apt. With or without anything attacking grasses, though, destabilizing the climate that has existed for as long as farming has existed will destroy the global agricultural network on which the existence of cities depends.
To see what life will be like when cities collapse, try to find a copy of that movie.