Natural and human systems of the Andes under climate change: local detection and attribution assessment of impacts in physical, biological and human systems

Physical, biological, and human systems in mountain regions are highly sensitive to climate change due to strong feedbacks and low resilience. Detection of changes and attribution of them to climate and non-climate drivers provides ongoing monitoring of complex interactions of coupled natural and human systems and improving scientific assessments that inform mitigation and adaptation practices. In the IPCC 5^th Assessment Report published in 2014, Central and South America was the region with the least evidence available for detection and attribution (D&A) of climate change impacts. Since then, much more evidence has accumulated due to an increasing number of studies detecting impacts in the Andean region. In this study, we therefore performed a systematic literature review of climate change impacts and made a local D&A expert impact assessment for a total of 12 natural and human systems in the Andes. We found the following confidence levels of detection and attribution of each impact for each system: medium and high, respectively, for energy; high and high, for snow and ice, tourism, and cultural values; high and medium for terrestrial and aquatic ecosystems, disasters, human health and migration; and medium and medium for agriculture and water systems. A total number of 65 sample impacts (in aggregate or case study form) could be attributed to climate change. Climate change was especially important in glacio-hydrological systems (49%) and terrestrial ecosystems (15%). Among the impacts that could be attributed to climate change with high confidence, snow and ice system dominated. About half of the total impact samples were attributed with medium confidence, of which 35% corresponded to water systems and 16% to agriculture. Finally, 14% of all impacts were assessed with low attribution confidence. Important results include: (1) glacier retreat leads to important cascading effects affecting most of the systems in the Andes; these impacts were primarily attributed to temperature increase caused by anthropogenic climate change; (2) numerous terrestrial and aquatic Andean ecosystems have been affected by climate change (e.g. upward plant colonization, changes in the abundance and distribution of species), and most of these impacts could be attributed to anthropogenic climate change; and (3) community changes and loss of cultural values are among the strongest impacts of human systems that were attributed to climate change; a broad set of studies detected that Andean communities perceived changes in their highly preserved long-standing cultural and spiritual rituals and cosmovision. These findings are key to understand current climate change impacts in the Andean region, and to advance our understanding of complex interactions of coupled natural and human systems in order to put particular attention on integrated scientific assessments and leverage local decision-making and management practices.