Human activities have markedly altered the pattern and trend of net primary production in the Ili River basin of Northwest China under current climate change

Abstract

AbstractThe Ili River basin (IRB), as an epitome of border areas of Northwest China and has experienced intensive human disturbance since the implementation of the Western Development Strategy in 2000. However, the ways that human activity affected the pattern and trend of net primary production (NPP) in this region under current rapid climate change remain unclear. Here, potential NPP time‐series data, driven solely by climate change, were simulated using a process‐based model IBISi, with an initial status that was already disturbed by human activity prior to the measurement period. The human impacts on NPP during the measurement period were derived by comparing potential NPP with remotely‐sensed ones. The results indicate that human activities have markedly altered the pattern and trend of NPP in the IRB during 2000–2017. Cropland reclamation and cultivation, and afforestation, have resulted in significant increases in NPP relative to their typically low values in the basin bottom areas. Associated with those changes grazing has caused negative deviations in most grasslands with potentially high NPP. As a consequence, the spatial heterogeneity of NPP was significantly lowered. A slight decreasing trend in NPP of the IRB was revealed by remote sensing, which contrasted the increasing trend that should have occurred due to climate change. This difference between the real and simulated trends was mainly attributed to a weakening of positive human impacts on NPP in croplands and strengthening of negative impacts in grasslands. These findings provide valuable information for current land‐use management and ecosystem restoration in Northwest China and Central Asia.