sustainability Article Economic Valuation of Earth’s Critical Zone: A Pilot Study of the Zhangxi Catchment, China Wan Nie 1,2 , Hongyan Guo 3, Lei Yang 4, Yaoyang Xu 5, Gang Li 5, Xiaohong Ruan 6, Yongguan Zhu 4, Liding Chen 4 and Steven A. Banwart 1,7,* 1 School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK;
[email protected] 2 Health Economics Group, University of Exeter Medical School, University of Exeter, Exeter EX1 2LU, UK 3 State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210046, China;
[email protected] 4 State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China;
[email protected] (L.Y.);
[email protected] (Y.Z.);
[email protected] (L.C.) 5 Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Ningbo 315830, China;
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[email protected] (G.L.) 6 Key Laboratory of Surficial Geochemistry, Ministry Education, Nanjing University, Nanjing 210023, China;
[email protected] 7 Global Food and Environment Institute, University of Leeds, Leeds LS2 9JT, UK * Correspondence:
[email protected] Received: 17 January 2020; Accepted: 19 February 2020; Published: 24 February 2020 Abstract: Earth’s critical zone is the physical layer contained between the top of the vegetation canopy and the depth of the circulating groundwater below the land surface. The critical zone is defined within the study of Earth natural sciences as the unique terrestrial biophysical system that supplies most life-sustaining resources for humans.