A subgenre of this is ecotopian fiction, where the author posits either a utopian or dystopian world revolving around environmental conservation or destruction. Danny Bloom coined the term "cli fi" in 2006, with a Twitter boost from Margaret Atwood in 2011, to cover climate change-related fiction, but the theme has existed for decades. Novels dealing with overpopulation, such as Harry Harrison's Make Room! Make Room! (made into movie Soylent Green), were popular in the 1970s, reflecting the popular concern with the effects of overpopulation on the environment. The novel Nature's End by Whitley Strieber and James Kunetka (1986) posits a future in which overpopulation, pollution, climate change, and resulting superstorms, have led to a popular mass-suicide political movement.
While eco-dystopias are more common, a small number of works depicting what might be called eco-utopia, or eco-utopian trends, have also been influential. These include Ernest Callenbach's Ecotopia, an important 20th century example of this genre. Kim Stanley Robinson has written a number of books dealing with environmental themes, including the Mars trilogy. Most notably, however, his Three Californias Trilogy contrasted an eco-dystopia with an eco-utopia, and a sort of middling-future. Robinson has also edited an anthology of short ecotopian fiction, called Future Primitive: The New Ecotopias.