Andean lakes: endangered by natural and anthropogenic threats

The Andes mountains extend north–south in a latitudinal gradient of 8500 km. Because of the great climatic variety and the peculiar north–south orographic distribution, lakes are highly diverse, including different lake origins and contrasting morphometries. We reviewed >700 ecological studies on Andean lakes to identify the main threats to these freshwater systems. The most important threats are UV radiation, changes in water balance, and eutrophication, all 3 interacting with climate change, alien species introductions, and mining. UV radiation is an important factor in Andean lakes not only because of the altitude but also because many lakes are included in the Antarctic ozone hole. The introduction of alien species, particularly exotic salmonids, also had detrimental effects, affecting native fish populations and behaviour and endemic species by disrupting the indigenous food web. Eutrophication and browning caused by human activities, including land use interacting with climate change, are increasing in Andean lakes, causing a decrease in water quality. Finally, mining can cause water contamination (both groundwater and surface water) by chemicals emitted from mining processes, thus producing a loss of biodiversity. Although an important number of Andean lakes have been declared as Ramsar sites because of their uniqueness and their extreme conditions, they are subject to significant human impacts. Here, for the first time, we identify these impacts all along the Andes; however, further studies at different scales are mandatory if we hope to understand, conserve, and manage Andean lakes.