Abstract <p>The effect of climate changes on productivity of the aboveground phytomass of steppe plants on Vodnyi Island of Manych-Gudilo Lake in the Rostovskii Reserve was analyzed. In the period 1991–2022, the mean annual temperature in the study area increased, on average, by 0.07°C/year, and the annual precipitation decreased by 1.93 mm/year. The de Martonne aridity index decreased significantly (by 1.16 per year, on average), which indicated arid warming. Temperatures increased in all seasons, while precipitation shifted from summer and autumn to winter and spring against the background of a general decrease. The structure of the vegetation cover was dominated by grasses, the share of which averaged 62%. The effect of precipitation on the total productivity of the phytomass was the leading one and amounted to 51.3%. The overall decrease in precipitation favored a decrease in the phytomass of the studied plant groups, except for cereals, the productivity of which became greater with an increase in precipitation in winter and spring. These changes resulted in a further increase in the proportion of grasses in the plant cover of steppes on Vodnyi Island and to a decrease in the participation of other families. The revealed climatic trends will contribute to a drop in the productivity of the aboveground phytomass of steppes on Vodnyi Island, of grasses, in particular.</p>