A critical natural service is nutrient cycling, the
circulation of chemicals necessary for life from the environment
(mostly soil and water) through organisms
and back to the environment (Figure 1-4, p. 9).
一個關鍵的自然服務是維持生命的化學必需品的養分循環，從環境(主要是土壤和水)通過生物體再回到環境。
