Monocultures are large areas of land on which only one type of plant is grown. There are tree monocultures as well as crop monocultures. There are dangers associated with this approach to agriculture, especially environmental ones.
1. A monoculture is very vulnerable. It can be wiped out completely by one virus, fungus, destructive insect, or other [...]
Source: http://www.gagazine.com/the-dangers-of-monocultures/