Impacts, carbon effects, and forecasts for cropland expansion in the Northern Tianshan Mountain Economic Zone

Increasing population growth and cropland occupation means that new cropland is needed to achieve the goal of food security. In order to achieve the goal of "carbon neutrality," the carbon effect and ecological effect brought about by the cropland area increase urgently need to be studied. Methods such as land use transfer matrix, land use information map, InVEST model, and the ecological risk index were used to analyze the impact of cropland change in the Northern Tianshan Mountain Economic Zone and calculated the carbon effect caused by its increasing cropland area. The Ca-Markov model was used to predict and analyze the impacts of future cropland distribution and area. The results showed that, between 2000 and 2020, the area of cropland in the study area increased 3926 km2, and the area of cropland occupation by built-up was 857 km2. The new increased cropland was predominantly derived from low-cover grassland and unused land. The quality and the carbon stock of the cropland increased. The ecological risk index of cropland was 0.2613, 0.2624, and 0.1187 in 2000, 2010, and 2020, respectively. The proportion of low-risk index area was 54.43%, 55.49%, and 87.22% in 2000, 2010, and 2020, respectively. According to the current development pattern of cropland, from 2000 to 2030, the area of occupation cropland and the area of cropland may increase, the carbon stock may increase by 941,650 Mg due to the change in land use types associated with cropland, the ecological risk index may be 0.1113, and the proportion of low-risk index cropland may be 80.08%. As a carbon sink, cropland is important for local carbon neutralization alongside the sustainable adjustment of planting structure and farming methods. The results could be helpful for land resource management policy, under the conditions of following natural laws; it is feasible to appropriately expand the cropland area in order to support the gradually increasing population.