Long-term comprehensive field investigations of landscapes on the territory of Donskoi Natural Park and Elton Natural Park in Volgograd oblast suggested the conclusions about the pyrogenic dynamics of geosystems. A monitoring has revealed that fires have a negative influence on steppe and desert steppe landscapes. It was determined that fires lead to a reduction in biodiversity of geosystems, an attenuation of the self-regulation processes and a decrease in resistance to external effects. It is found that the structure is simplified in steppe geosystems, the homogeneity of vegetation cover increases, the height of the grass stand overall projective cover decrease by a factor of 2–3 and 1.5–2, respectively, and woody-shrubby vegetation dies. The color aspects of steppe are only poorly pronounced. Frequent fires in virgin steppes cause changes in the phytocenosis structure, namely, mesophilic grasses and forbs disappear, Festuca valesiaca replaces Stipa, and sagebrush and other weeds invade territories. Biological productivity of geosystems decreases considerably within a long period (3–5 years). Consequences of the pyrogenic influence have been recorded. Aneolation and ablation come into action. Landscapes of calciphilous steppes and desert steppes suffer the most from the harm done by fire. It has been recorded that the most serious damage is inflicted by late summer and autumn fires when there is a considerable amount of leaf litter accumulated on the soil surface. It has been concluded that the pyrogenic transformation of geosystems presents the most serious threat to biological and landscape diversity of steppes.Keywords: fire, geosystem, landscape and biological diversity of steppes, pyrogenic transformation, specially protected natural territories, natural park.