In agriculture, monoculture consists of the planting and harvest of a single crop over a wide area of land. The idea was manufactured as a way to essentially flood the market with a certain type of crop to help lower the cost to the general public. While the idea certainly came from good intentions, clearing a wide land mass to plant a single crop changes the natural biodiversity of the land, and comes with negative impacts. As a result, things that are naturally kept in check by biodiversity such as pest control, healthy pollination, nutritious soil, and disease resistances are put into turmoil.
Miguel A. Altieri’s project, Agroecology in Action, does a good job explaining the problems associated with monoculture, as well as offers alternatives to conventional agriculture.