In Water-Limited Landscapes, an Anthropocene Exchange: Trading Lakes for Irrigated Agriculture

Lakes—quintessential features of Earth's surface prized from perspectives of water security, aquatic ecosystems, and recreation alike—are shrinking in water-limited regions of all of Earth's inhabited continents. Here we assessed Landsat-derived long-term decrease in global lake area relative to historical lake extent aiming to determine the role of recent Anthropocene levels of irrigated agriculture in the global phenomenon of lake desiccation. As of 2015, 11% (1.8 · 10⁵km²) of global lake area has already been lost, primarily due to increased water consumption in support of irrigated agriculture in endorheic basins within water-limited regions. However, current levels of irrigated agriculture portend substantial additional shrinkage of global lakes before reaching new equilibria with present-day inflows, with an additional 60–130% increase in endorheic lake loss anticipated. The time required for shrinking lakes to attain new equilibria ranges from decades to centuries depending on lake hyposometry. Even a small decrease in lake area can portend lake transition from exorheic to endorheic and dramatic reductions in water quality. Thus, lake area changes severely understate the perilous condition of global lakes. The watershed area contributing to shrinking (endorheic and exorheic) lakes accounts for 18% of Earth's land area, far too large for the irrigated agriculture therein to be transferred elsewhere in order to save these lakes, though continued developments in the efficiency of water consumption in agriculture and urban areas can save significant quantities of water. This suggests that global lake shrinkage may be a harbinger signaling mankind having exceeded Earth's sustainable carrying capacity.