EconPort - Values of the Natural World

Inputs of raw materials and energy
Operation as a Waste Assimilation Sink
Amenity values like the aesthetic of scenery plus recreation and other sources of utility.
Life-sustaining services such as the water cycle, the nutrient cycle, climate regulation, and maintenance of the atmosphere.
In addition, some economists add use and existence values to the equation. Use value requires some utilization of the environmental good (fishing or sightseeing in a park). Existence values are more intangible as non-use and are needed to measure benefits that people who never use the good get from just knowing the resource exists (a protected wildlife refuge in a far-off land).
Even more intangible, controversial, and hard to quantify is option value: the value placed upon a resource when its future supply or demand is uncertain.