Formation and Evolution of Black Soils: A Global Review

Recognized for their exceptional fertility and agricultural productivity, Chernozems, Phaeozems, Kastanozems, and Mollisols have attracted sustained scientific attention over the past century. However, much of this work has focused on degradation, conservation, carbon sequestration, and agricultural impacts, whereas scientific classification and global pedogenic factors have received comparatively less attention. Referred to collectively as ‘black soils’ for their characteristic dark color, these soils are often grouped together in public and academic discourse, even though they may differ considerably in origin, environment, and detailed classification. Drawing on more than 150 studies worldwide, this review synthesizes current knowledge of how black soils form and evolve across different regions of the globe. Specifically, we examine: (1) research trends in publication records; (2) formation ages and chronological development based on literature data; (3) pedogenic conditions shaped by key environmental factors and representative soil profiles; (4) principal proxies and methodologies used to investigate black-soil genesis; and (5) disturbance regimes such as wildfire, volcanic activity, and permafrost thaw. The accumulated evidence highlights both the remarkable difficulty and the slow pace of black-soil accumulation, where the formation of even 1 mm may require centuries. These insights emphasize the urgent need for greater scientific attention and for immediate measures to preserve and restore these critical resources. Advances in understanding pedogenic mechanisms, including humus accumulation, carbonate dynamics, and horizon differentiation, provide an essential scientific basis for conservation strategies to mitigate erosion, nutrient depletion, and organic matter loss in black-soil regions.