Natural environment means all living and non-living things occurring naturally, meaning not because of humans. The universe is natural, but often the term "natural environment" only means nature on Earth.
Two aspects are usually included::
Ecological units which are natural systems without much human interference. These include all vegetation, microorganisms, soil, rocks, atmosphere, and natural events.
Universal natural resources and physical phenomena which lack clear-cut boundaries. These include climate, air, water, energy, radiation, electric charge, and magnetism.
There is also the built environment. There, man has changed landscapes and natural environment to make cities and agricultural land.
