Philip José Farmer wrote three stories about the future of mankind, where overpopulation or pollution threatens our existence.

The three stories offer different solutions.
In the Hugo Award winning "Riders of the Purple Wage" (1967) everyone receives the purple wage, you do not have to work. People live in an economy of abundance.
In "The Sliced-Crosswise Only-on-Tuesday World" (1971) the overpopulation is solved by 'stoning' the people. You only live one day a week, the other six days you're 'stoned' (suspended in a cylinder).

The third story, "Seventy Years of Decpop" (1972), offers the most dark and gloomy solution for overpopulation and pollution. Mankind is decimated by forced sterilization. This is not the best one of Farmer's three stories. The last third part reads more like an essay, with statistics, than as a story. It still, like the other two, offers some thoughts about our future to think about.

A dog named Ralph von Wau Wau. A speaking dog, a German Shepherd, with an IQ of 200. And this Ralph is a private detective. Philip José Farmer had some crazy ideas for his stories, but this is one of the most bizarre.
The story "A Scarletin Study", Ralph's first case, is a Sherlock Holmes pastiche, a very hilarious one.
A painter is missing and his beautiful wife asks Ralph to find him. The solution is hidden in the painting it seems...

Farmer planned to write several stories in the Ralph von Wau Wau series, but only two were published. "The Scarletin Study" (1975) – the story we are talking about above – and "The Doge Whose Barque Was Worse Than His Bight" (1976). It's a pity he never came to write more.