Climatic and human impacts on Patagonian terminal lakes.

We study the causes of the reduction in the surface area of five terminal lakes since 2007, within Laguna Blanca National Park, a Ramsar site in Patagonia (Southern South America). The terminal lakes in this park are critical habitats for several species of animals, some of which are endemic and endangered. We analyzed the lakes' area time series (1998-2024), a climatic index determining dry and wet periods, and human land use changes in the basin of the lakes. The area of the five terminal lakes decreased between 20 and 52 % since 2007, with a higher reduction in the smaller lakes. From 2007 to 2024, the months with dry conditions increased by 29 %, and the months with wet conditions decreased by 13 %, compared to 1998-2006. Moreover, since October 2020, fifty-three (53) irrigation channels have been constructed on the basin of Laguna Blanca Lake. Before the construction of the channels, Laguna Blanca Lake had already decreased by 19 % compared to 2007. The other four terminal lakes are outside the sub-basin affected by the channels. Therefore, the reduction in the surface area of all the terminal lakes was primarily due to an increase in dry conditions. However, the irrigation channels may accelerate the desiccation of Laguna Blanca Lake. As in our study, several terminal lakes are globally drying quickly due to climate change and human impact. This study shows international and local discussions are needed to prevent the disappearance of terminal lakes, as they are impacted even when located on protected land.