Value from knowing environmental goods exist independent of use or option value. If we lose a species in the wild, such as the Bengal tiger, very few of us will have our welfare directly affected by not being able to see it, photograph it or hear it. That "use value" is very small. But many people will lose the option to do that in the future, should they care to. Economists call that "option value." Further, many people around the world derive some benefit just from knowing that Bengal tigers exist in the wild. That is "existence value."
EXISTENCE VALUE
Meaning of EXISTENCE VALUE in English
Environmental economics English glossary. Английский глоссарий экономики окружающей среды. 2012