In the field of ecology, a natural system is one that exists in nature, independent of any human involvement. The natural system consists of all the physical and biological materials and their intertwined processes
Human systems or social systems exist alongside and interact with natural systems in many ways. Natural systems may be studied and used and even duplicated, however in that case they become artificial systems. Fundamental natural systems remain unchanged by human attempts at duplication or imitation.
The study of natural systems is important to several fields, agriculture being one of them. Agriculture is an example of an artificial (man-made) system that is introduced into an existing natural system. While the agricultural system operates according to its man-made schedule and processes, it is nonetheless affected by fundamental natural processes such as weather, the ability of soil to produce crops, the feeding patterns of livestock and others.
The study of the complex interactions of human societies and natural systems has become increasingly important in the 21st century. Formerly, the two disciplines of sociology (the study of human society) and ecology were formally separated but the relationships between human activity and the natural environment are crucial to solving environmental issues.