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

Abstract

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 · 10 5 km 2 ) 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.Plain Language Summary Today, a host of processes influence the terrestrial water balance.These processes drive the observed shrinkage of lakes in water-limited regions of all inhabited continents. Typically, lake shrinkage is attributed either to climate change or unsustainable increases in human water consumption. However, while drivers of lake desiccation have been explored for individual lakes, the causes of this phenomenon have not been explored at the global scale. We therefore propose a simple conceptual model in which lake area and agricultural area are exchangeable in closed basins. We find that this simple model accurately determines the role of agriculture in loss of endorheic lakes. This model demonstrates that irrigated agriculture is the primary driver of desiccation of global lakes.

Overview of past, current, and future ecosystem and biodiversity trends of inland saline lakes of Europe and Central Asia

“…In many arid parts of the region, especially in Central Asia, changes in lake surface area are caused by factors related to land use change. Chief among these factors is the extraction or diversion of water for agriculture, which would otherwise flow into terminal lakes (Bai et al 2011, Wine andLaronne 2020). Reservoir and dam construction is another type of human interference that has affected both the runoff regime and volume of flow into lakes and outlets (Nilsson and Berggren 2000, Pueppke et al 2018, Schmutz and Moog 2018.…”

Post-Soviet changes in cropping practices in the irrigated drylands of the Aral Sea basin

“…Globally, the surface area of many endorheic lakes is shrinking, a process in which irrigated agriculture plays a key role (Wang et al 2018, Wine andLaronne 2020). The Aral Sea is a paradigmatic example of the destiny of a terminal lake that shrank due to a grossly reduced water inflow caused by excessive water extraction for agriculture.…”

Implementation and Evaluation of Irrigation Techniques in the Community Land Model

“…In the High Plains in the USA, the water level of aquifers has declined substantially due to the large irrigation water withdrawal (McGuire, 2014). A study focusing on global lakes revealed that ∼11% of the lake area has been lost until 2015 mainly due to irrigation water withdrawal (Wine & Laronne, 2020).…”