Cascading risks and robust adaptation in the tropical Andean glacier-fed systems

Climate change and glacier retreat in the tropical Andes are transforming mountain hydrology and challenging water security for both upstream communities and large downstream cities. Most research and policies have focused on declining glacier contributions during the dry season, as the loss of buffering capacity threatens water supply for drinking, irrigation, and hydropower. However, glacier shrinkage is also reshaping water quality: as ice recedes and exposes sulfide-rich bedrock, oxidation generates acid rock drainage, reducing pH and mobilizing metals. In several basins (e.g. the Santa River Basin - SRB), this has already led to regulatory bans on the use of historically important rivers for drinking water unless costly treatment is installed, constraining water access well before projected declines in water volumes. Beyond physical impacts, glacier loss has profound cultural and social consequences. High-mountain glaciers hold strong spiritual significance for Indigenous communities; their disappearance disrupts rituals, alters pilgrimage routes, and erodes place-based identities, ultimately shaping how communities perceive and respond to water insecurity. Recent work further demonstrates that glacier retreat has measurable economic consequences for water-dependent sectors. For instance, in the SRB, results indicate that glacier retreat alone can account for up an additional 15% of economic losses in the agriculture and hydropower production sectors.

To address these complexities and uncertainties in future water security, our recent work has focused on supporting robust adaptation planning. We apply robust decision-making and exploratory modelling approaches to test portfolios of adaptation measures, across wide ranges of climate and socioeconomic conditions. Rather than targeting a single “most likely” future, we identify combinations of measures that provide sustained performance in uncertain and evolving contexts while reducing the risk of maladaptation. A key insight is the need for stakeholders to explicitly negotiate thresholds of acceptable loss and damage for both water quantity and quality to guide water governance choices. Building on this foundation, we now plan to expand our research to systematically examine how glacier-related hazards propagate through interconnected social-ecological systems. Using conceptual frameworks on cascading and compound risks, we will analyze cross-sectoral impacts on domestic supply, agriculture, hydropower, and cultural values, and assess how responses in one sector may amplify vulnerabilities in others. This work aims to identify leverage points for adaptation that strengthen resilience rather than shifting or creating risks, supporting long-term resilience in the Peruvian Andes and other rapidly changing mountain regions.