Monoculture is a technique, primarily used in agriculture or silviculture as a means of increased efficiency of human actions. Monoculture began with the commencement of agriculture by planting and harvesting cereal crops, when other plant species were first identified as weeds and removed to prevent competition and make cultivation easier. In its modern form, it is represented by large fields of single crops (sometimes grown year after year), by orchards of few varieties of fruit, by forests of single species of trees, or by by large barns or feedlots where animal husbandry is concentrated in large numbers of animals. Such concentrations may occur because of highly favorable natural conditions for a crop, such as the almond growing region of California, or the apple belts on the lee side of Lakes Michigan and Ontario. Naturally occurring monoculture is relatively rare; occasional ecosystems that appear to be natural monoculture generally are only an illusion or are created by an artificial disturbance. A climax forest of longleaf pine in Southeastern United States appears as monoculture in casual observance of the dominant tree species, but closer observations reveals a rich biodiversity of smaller species. In a few settings invasive weeds have so completely outcompeted other species that an unintentional monoculture setting may result. Monoculture is seen as increasingly problematic to biologists because of several inherent problems, first an foremost being that it is the opposite of the desirable condition of biodiversity. Monoculture crops or animal husbandry may increase susceptibility to diseases and pests, Monoculture often requires a large amount of input in the form of chemical pesticides - and may be susceptible to pest population explosions due to loss of biological control agents. Pine monoculture increases susceptibility to wildfire and pine borers. Animal husbandry may depend of prophylactic treatments of antibiotics, resulting in unwanted side effects on human health due to traces of these that remain in meats or milk. Monoculture may deplete soils, or may require artificial concentrations of pollinators during bloom time, while creating a barren or toxic environment for pollinators for the rest of the season.