Examples of monocultures include lawns and most field crops, such as wheat or corn. The term is nonspecific, so things such as large-scale confined animal feeding operations (CAFOs) might be included.
The drawbacks and risks of excessive use of a single species are acknowledged and well understood in agriculture and agricultural science. Cropping systems such as crop rotation and especially pastures address some of these drawbacks.
Extensive monoculture of fruits, cucurbits, alfalfa seed and other crops tends to produce pollination problems, because pollinators cannot use all the resources available during bloom, and they may starve during the rest of the season. Such pollination problems are solved by pollination management.
Some native areas, such as climax forests, show remarkably little species biodiversity. These areas are the exception rather than the rule, however.
Monocultures are derided by the environmental movement both because of their susceptibility to disease and insects, and because of the large amount of chemical inputs often required to sustain them. The movement seeks to change popular culture by redefining the "perfect lawn" to be something other than a turf monoculture, and seeks agricultural policy that provides greater encouragement for more diverse cropping systems. Local food systems may also encourage growing multiple species and a wide variety of crops at the same time and same place.
A monoculture can also be any sort of system wherein everyone is wearing/doing/seeing/reading/watching/thinking the same thing.