"And what haunts me, is that in all the faces of all the bears that Treadwell ever filmed, I discover no kinship, no understanding, no mercy. I see only the overwhelming indifference of nature. To me, there is no such thing as a secret world of the bears. And this blank stare speaks only of a half-bored interest in food."
You've found yourself alone in the woods. No big deal, nature is a perfectly fine place to spend some time, wandering around. But now you can't see the edge of the forest anymore. And you realize that you can't see the sun, either, so you can't tell which direction to go in to get out. Let's add some scary strange noises. Watch yourself randomly running in some direction, looking for a way out, screaming for help, as the sun goes down and afternoon turns into dusk, which turns into a moonless night. You are so screwed.
The truth is, nature isn't cruel; it just doesn't care about you. The forest is a big scary place in which you can get lost, or killed by disease or wild and ferocious animals. The desert has only about a hundred ways for you to be injured or die. The jungle is even worse. Even a lake or a river is a dangerous place for a person who isn't prepared.
This trope comes into play when a work's creator chooses to use that fact, that nature is a dog-eat-dog environment full of disease, natural disasters, parasites, predatory animals, killing and other ghastly things, rather than romanticizing it or portraying nature as harmonious or maternal. The focus is on the horror, danger, amorality, and ruthlessness of untamed nature.
Compare Death World. Contrast Ghibli Hills; inversely related to All-Natural Snake Oil.
In the New DC Universe, Alec Holland gave up trying to replicate the formula that gave him his powers because of this. The plant world is dangerous, and submersing Earth in it would be a disaster.
In Sin City, Marv has an Internal Monologue commenting on perceptions of nature. He note that most people consider nature something beautiful and friendly, and remarks that they have probably never spent a night tied to a tree in the woods. Marv is one of the most violent, dangerous men in a series entirely filled with violence and danger, and he is terrified of the woods.
Werner Herzog appears to be of this opinion, as can be seen in several of his films. His ending narration to Grizzly Man perhaps puts it best.
While it's not abundantly clearin the film itself, this trope was one of the main inspirations behind Lars von Trier's Antichrist. Von Trier has stated in interviews that he was moved by a nature documentary he once watched which treated the animal world as a kind of barbaric, earthly hell, in stark contrast to the more idyllic portrayal common to fiction. Which brought us gems like a stillborn fawn, demonic forest animals, and ominous lines like, "The forest is the devil's church."
Blackfish seems to make a point to contrast the sugary family-friendly SeaWorld TV commercials with orcas performing tricks and being petted by trainers to the terrifying footage of orcas attacking the trainers and sometimes each other. Although the film also presents the whale's natural environment as being a relatively harmonious one.
The book and film Into The Wild, which chronicles the experiences of Christopher McCandless, a young and idealistic college graduate who abandons everything for attempting to live off the Alaskan wilderness. Christopher slowly realizes this trope's truth as his supplies dwindle and it becomes evident that he was very poorly prepared for his adventure, ending up starving to death.
The Grey follows a group of plane crash survivors lost in the Alaskan wilderness. The freezing weather, lack of food, and presence of wolves are all treated as completely impersonal rather than actively malicious, and the main character's Rage Against the Heavens moment makes his helpless fury in the face of such indifference very clear.
After she is nearly killed by the indigenous life in the rainforest, Rachel goes on a tirade screaming that the rainforest that so many environmentalists want to save is nothing but a den of horrors. As far she's concerned, everyone would be better off if the entire rainforest was paved over with shopping malls. However, after morphing into a jaguar and seeing how much life there is on it, she admits that it is beautiful and she doesn't want the rainforest to be paved anymore... if only because now as an apex predator she has nothing to fear from the jungle.
Rainbow Six the Horizon Executive plans to wipe out humanity with a virus, so he and a selected few would be left to inherit the Earth. When Rainbow Six tracks them down in South America and destroys their compound, they are left in the jungle without clothes or tools. According to the epilogue they didn't last long, which goes to show that nature doesn't care if you have it's "best interest" in mind when choosing who survives or dies.
A common theme in Carl Hiaasen's novels are antagonists so used to modern convenience and so woefully ignorant of nature that they can't set one foot in the Everglades without getting instantly lost, injured, or eaten.
Exploited in Daughter of the Lioness when Nawat Crow and his band get rid of some people by stripping them naked and putting them in the middle of the jungle.
Live Action TV
The Life And Times Of Grizzly Adams uses this trope as a primary source for action as Adams and his friends often have to rescue visitors who learn the hard way that the wilderness is a dangerous place to be in if you don't know what you're doing.
This is the reason Green magic in Magic: The Gathering isn't a "good" color. There are many cards that reflect the lifegiving and nurturing facet of Mother Nature. There are also many cards that reflect Mother Nature's brutality.
In some ways, this is the heart of early gameplay in Minecraft. There is no real enemy or driving plot; it's just your struggle to survive in a hostile wilderness where the wild animals happen to be monsters.
The Spriggans from The Elder Scrolls are aggressive nature spirits that attack anyone who disturbs their groves. Another example from the same series is the Daedric Prince Namira, who represents the darker aspects of nature.
The Everfree Forest from My Little Pony: Friendship Is Magic, filled with dangerous animals such as the wooden Timberwolves, fits the role of "real" nature in a setting where the ponies themselves have a direct and semi-magical role in running most of their world's ecosystems and do so in the stereotypical harmonious way.
In the Futurama episode "Naturama", the characters appear as different animals in three segments of a nature documentary show. They either die, or their efforts prove to be pointless, or both. The narrator draws the lesson: "For in the end, nature is horrific, and teaches us nothing."
The episode "Rainforest Shmainforest" of South Park in which the kids get lost in the rainforests of Costa Rica, and they are attacked by big bugs, wild animals and hostile tribesmen, until they are saved by the "good" loggers who are clearing the forest.
In Family Guy, The quote at the top of the page comes from a nature documentary as narrated by a stereotypical black guy. It shows a cheetah hunting down some prey.
Damn, lookat dat sumbitch go! He haulin' ass! Dat thing come by my house, I killit! That little rat-lookin' thing just got ate! DAMN NATURE, YOU SCARY!