摘要：The Earth's ecosystems provide myriad goods and services that are essential to human wellbeing. This paper offers a typology of ecosystem services that emphasizes the means by which humans experience the service rendered. The typology distinguishes between services that are directly experienced, and those that are indirect. The paper offers an illustration of how indirect services can be valued when they contributed to production of a marketed product. The intermediate product method described is amenable to indirect services that are one stage removed (Tier 2), two stages removed (Tier 3), or even farther removed from the direct services that humans experience. The intermediate product approach to ecosystem service valuation is illustrated by an example of biological pest management to support soybean food production.
