Ecosystem
functions – the physical, chemical, and biological processes or
attributes that
contribute to the self-maintenance of the ecosystem; in other words, what the ecosystem
does. Some examples of ecosystem functions are wildlife habitat, carbon cycling, or
trapping nutrients.
Ecosystem
services – the beneficial outcomes, for the natural environment, or for
people, that
result from ecosystem functions. Some examples of ecosystem services are support
of the food chain, harvesting of animals or plants, clean water, or scenic views. In order for an ecosystem to provide services to humans,
some interaction with, or at
least some appreciation by, humans is required.
Equivalent
variation - the amount
of money that leaves a person as well off as they would be
after a change. Thus, it measures the amount of money
required to maintain a personÕs satisfaction,
or economic welfare, at the level it would be at after a change.
Existence
value – the value that people place on simply knowing that something
exists, even
if they will never see it or use it.
Externalities - uncompensated side effects of human
actions. For example, if a stream is
polluted by runoff from agricultural land, the people downstream experience a negative
externality.