Talk about all he possible ways in which impact on the environment by humans can be calculated (measured).

Several statistical measures called environmental Indicators
have been devised by the scientists to assess the state of the environment. This state need not
be necessarily the result of the impact of human activities, but usually human activity has
substantial impact on the state of any environment within which the activity takes place. These
indicators do not actually describe the state of the environment in detail. Rather they provide
information on some specific aspect of the environment which is indicative of the more detailed
state of the environment. For example a measure like average global temperature is used a measure
to describe global environment as it impacts so many different aspects of the environment
including size of polar caps, sea water levels and area submerged by the sea, and impact on life
of flora and fauna.

Some major environmental indicators include the
following:

• Atmospheric
  temperature


• Concentration of ozone in the
  atmosphere


• Amount of greenhouse gas
  emissions


• Ocean acidification
  levels


• Presence of of specific chemicals or toxins in water, land,
  atmosphere.


• Presence of of specific chemicals or toxins in plants
  and animals used as food.


• Population/density of different types of
  flora and fauna


• Desertification or the extent of land covered by
  deserts


• Noise levels


• Smog
  levels