I recall a story about a self-replicating organic compound that inhibited the evaporation of water.. accidentally released into the world's oceans, and causing catastrophic drought conditions, turning the entire planet into a desert..
There have been many stories of Post-Armageddon Earth, destroying civilization in varying degrees, with nuclear war, pollution, galactic clouds, meteor strikes, plate tectonic shifts, magnetic poles shifting, overpopulation and.. Alien Invasion..
I'd rather not meet (meat?) anyone from "out there" for another 1,000 years or so.. maybe longer..
Humanity needs a couple of dozen inhabitable planets under our control before we meet (meat?) anyone else..
Did I mention R.U.R.? ( Rossum's Universal Robots.. "To Serve Man and Keep Him From Harm" )