Accounting for monogastric livestock as a driver in global land use and cover change assessments

Land systems are described based on various characteristics, including land cover composition and agricultural production. However, it is uncertain to what extent livestock, particularly monogastric livestock, determines land systems. We included monogastrics in a land system classification, and statistically analyzed the land cover composition and agricultural production of otherwise similar land systems with and without monogastric livestock. The results indicate that land systems with monogastrics are statistically different from their counterparts in the classification without monogastrics in terms of grassland area and crop yields, but are less different in terms of tree area, crop area, and ruminant livestock production. We then used a land systems map that includes monogastrics in the classification and a similar map that does not include monogastrics to project future changes in a novel manner that integrates livestock as a determinant of land systems. The results show that including monogastrics in otherwise similar projections yields less cropland intensification and more cropland expansion in several world regions, including Northern Africa and the Middle East. Other regions, such as Europe and Australia, were characterized by less decrease or more increase in tree area in the application with monogastrics, mainly due to the occurrence of open forests with monogastrics. This study prompts a call for improved characterization of land systems for land use and cover change (LUCC) assessments in order to better represent LUCC driven by monogastric livestock.

土地系统可基于多项特征进行界定，涵盖土地覆被构成与农业生产状况。然而，目前尚未明确家畜——尤其是单胃家畜（monogastric livestock）——在多大程度上塑造了土地系统的格局。本研究将单胃家畜纳入土地系统分类体系，并对包含与不包含单胃家畜的同类土地系统的土地覆被构成及农业生产状况开展了统计分析。研究结果显示，在统计层面，包含单胃家畜的土地系统与分类体系中不含单胃家畜的对应土地系统在草原面积与作物单产方面存在显著差异，但在林木面积、作物种植面积及反刍家畜（ruminant livestock）生产方面的差异则相对较小。随后，本研究分别采用纳入单胃家畜分类的土地系统图谱，以及未纳入单胃家畜的同类图谱，以将家畜作为土地系统决定因子的创新范式，对未来土地系统变化进行情景预测。结果表明，在同类情景预测中纳入单胃家畜变量后，北非、中东等全球多个区域的耕地集约化程度有所降低，而耕地扩张规模则有所提升。欧洲、澳大利亚等其他区域在纳入单胃家畜的分析场景中，林木面积的降幅更小甚至增幅更高，这主要源于包含单胃家畜的疏林景观的存在。本研究呼吁学界进一步优化土地系统的特征界定方法，以服务于土地利用与覆被变化（LUCC）评估工作，从而更精准地刻画由单胃家畜驱动的土地利用与覆被变化过程。