Assessing Environmental Sustainability Based on the Three-Dimensional Emergy Ecological Footprint (3D EEF) Model: A Case Study of Gansu Province, China

Quantifying the supply and demand relationship between human social consumption and natural ecosystem resources is an effective way to assess the sustainability of ecosystem services. This paper introduces the concepts of footprint size (EFsize) and depth (EFdepth) to emergy analysis to establish a three-dimensional emergy ecological footprint (3D EEF) model and evaluates the environmental sustainability development of Gansu Province from 2001 to 2020. The results show that the minimum value of the 3D emergy ecological footprint (EEF3D) of Gansu Province was 5.98 x 10(7) hm(2) and that the maximum value was 1.41 x 10(8) hm(2). The EEFdepth was slightly more than one in 2015 and 2016, and the ecological resources were in deficit. However, the ecological service system from 2001 to 2020 was almost in a sustainable state. The region's emergy carrying capacity (ECC) and emergy ecological footprint (EEF) from 2021 to 2030 are predicted using the ARIMA and GM (1, 1) models. The projections show that the ECC and EEF will increase year by year from 2021 to 2030. In the short term, the flow of natural capital can satisfy the development requirements. Finally, policy recommendations are provided for the ecological sustainability of the region.