The causes of monocultures are the economics of global product of agriculture, standard of industrial society, and the apparent “simplicity” of managing only one crop.
The major cause of the loss of top soil is soil erosion (which is caused by the factors like water, wind and tillage of farm fields). Loss of top soil become a global problem for agriculture.
A species that are occurring outside of its normal distribution are known as Alien species. The cause of alien species is that these species are not native to ecosystem and they can cause harm to the environment.