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. A feature of this specific physical system that is defined by geographical locale is the interactions of people with the vertically-connected biophysical flows and transformations (energy, material, biodiversity) that contribute to human welfare by delivering, both directly and indirectly, critical zone services to humankind. We have characterized these interactions by considering the full extent of the critical zone through the application of economic valuation methods. We estimated the current economic value of 14 critical zone services for 5 biophysical components of Earth’s critical zone, based on data collected from the Zhangxi catchment of Ningbo city located in the Yangtze River Delta region of China and from several additional published studies. For the full vertical extent of Earth’s critical zone bounded by the Zhangxi catchment, the value, most of which is outside the market, was estimated to be USD 116 million in 2018. Valuation of goods and services was delineated for benefits arising from key components of the critical zone physical system. The estimated value of the atmospheric component of Earth’s critical zone was USD 5 million; the vegetation component value was USD 96 million; the soil component value was USD 8 million; the surface water component value was USD 5 million; and the groundwater component value was USD 2 million. Because of the nature of the uncertainties and lack of data for the full range of identified services, these values are considered a minimum estimate. Gross domestic product in the Zhangxi catchment was around USD 431 million in 2018. These results illustrate, for one location, the range of services that arise when considering the full depth of Earth’s critical zone, the data needs for valuing this range of services, and the conceptual and potential methodological advances, and the challenges, that exist at the disciplinary interface between Earth natural sciences and applied economics.
Economic valuation of Earth's critical zone: Framework, theory and methods
