Recent progress in studies on land cover change and its regional climatic effects over China during historical times

The recent progresses on the reconstruction of historical land cover and the studies on regional climatic effects to temperature, precipitation, and the East Asian Monsoon across China were reviewed. Findings show that the land cover in China has been significantly modified by human activities over the last several thousands years, mainly through cropland expansion and forest clearance. The cropland over traditional Chinese agricultural areas increased from 5.32x10⁵ km² in the mid-17th century to 8.27x10⁵ km² in the mid-20th century, while the forest area over the Chinese mainland had been reduced by 1.66x10⁶ km² during the last 300 years. These changes of land cover have been detected as an important driving force of climate change by simulations of climatic effects based on various climate models (including RegCM3, RegCM2-NCC, RIEMS version1, MM5 version 2, and AGCM+SSiB) with reconstructed historical land cover data or by contrasting current land cover to potential natural vegetation. The human-induced land cover changes over China have led to the enhancement of the East Asian winter monsoon, as well as cooling in winter and warming in summer approximately since 1700. However, the simulation results on annual mean temperature, precipitation, and the East Asian summer monsoon varied from model to model, which cannot be simply attributed to certain forcing so far, but undoubtedly, using different land cover datasets in various simulations played a key role. Thus, developing more accurate gridded historical land cover datasets on different regional scales with high time resolution is needed in the future.