Long-term terrace change and ecosystem service response in an inland mountain province of China

The exploration of terrace change and its associated ecosystem services (ESs) provides invaluable insights into the intricate interplay between engineering initiatives and environmental conditions. This understanding is crucial in designing strategic plans for environmental management. However, how terraced fields area change and influence ESs over an extended period at a regional scale remain relatively unknown. To bridge this knowledge gap, this study focused on terraces in Gansu Province (a typical inland mountain province), North-western China, by dividing the study area into seven regions, the quality and value benefits of unit area, the overall and cumulative of terraces were calculated for each region in Gansu province based on remote-sensing data, meteorological data, terraced area and benefits data. In this regard, the distribution, spatiotemporal changes and ESs associated with terraced fields in Gansu were examined from 1990 to 2020. The results show that: (i) terraces with the area of 2.20 x 104 km2 accounts for 81.34 % of counties(districts) of Gansu province in 2020, mainly located in the loess hilly and gully region (82.72 %). (ii) From 1990 to 2020, the terrace area in Gansu expanded from 8.13 x 103 to 2.20 x 104 km2, peaking at 636.73 km2/yr during 1990-2000, with notable spatial heterogeneity. (iii) In terms of ESs' quality benefits, soil conservation benefits of terraces were the most significant, reaching 91.30-98.32 % per unit area, the cumulative benefits (1990-2020) were 1.82 x 109 t, followed by water conservation benefits (42.12-89.20 % and 2.36 x 1010 m3). (iv) Terraces expansion have increased the ecosystem service value by 815.10 million Dollar ($), with regulating services and habitat services accounting for 34.92 % and 31.92 %, respectively. These results indicate that the enormous potential value of terraces in ecological environment governance and ecological economic benefits, and provide a scientific support for understanding terraces and leveraging their ecosystem functions, while also offering valuable insights for the conservation of global mountain ecosystems and the improvement of human well-being.