Systematic review of natural capital valuation: Emergy accounting and ecosystem service valuation

Natural capital refers to the stock of natural resources that generates flows of goods and services benefiting human well-being. Over the past 30 years, increasing attention has been paid to natural capital valuation and mapping. However, notable differences remain in how natural capital valuation is conceptualized, and systematic summaries of the valuation methods used are still lacking. We propose a concise conceptual framework that aims to clarify natural capital valuation and its relationship with ecosystem service valuation. We subsequently conducted a literature search, screening, and mapping of data related to natural capital valuation, ultimately identifying 54 relevant publications. These publications were classified into three categories according to different methods: M1 emergy accounting; M2 ecosystem service valuation; and M3 other methods. Existing assessments show that the monetary value of natural capital varies across regions. For example, illustrative case studies show that the monetary value of natural capital is increasing in the temperate climatic regions of China but is decreasing in Europe, with relatively limited monetary valuation assessments in tropical climatic regions. Existing publications show that the valuation results derived via emergy accounting methods are higher on average than those obtained from ecosystem service valuation. Our systematic review of natural capital valuation highlights the recent research hotspots and the similarities and differences in the results of different valuation approaches. This study can provide a reference for the selection of study areas and methods for future natural capital valuation research and support regional and global natural capital valuation.