In order for this to happen, conditions must be wet, acidic and cool. These conditions favour the growth of mosses, grasses and small shrubs but inhibit the microbial activity that usually breaks down the plant material.
As they die they are laid down and accumulate year on year rather than rotting away. Such conditions are found more frequently in the northern hemisphere where the vast majority of the worlds 400 million hectares of peat lands are to be found.
