Andean Lakes: endangered by natural and anthropogenic threats

The Andes mountains extend North-South in a latitudinal gradient of 8,500 km. Due to the great climatic variety and the peculiar north-south orographic distribution, lakes are very diverse, including different lake origins and very contrasting morphometries. Here, we reviewed more than 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, eutrophication, all three interacting with climate change, alien species introduction, and mining. Ultraviolet 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 pretend to understand, conserve, and manage Andean lakes.