The melting of tropical glaciers provides water resources to millions of people, involving social, ecological and economic demands. At present, these water reservoirs are threatened by the accelerating rates of mass loss associated with modern climate changes related to greenhouse gas emissions and ultimately land use/cover change. Until now, the effects of land use/cover change on the tropical Andean glaciers of South America through biomass burning activities have not been investigated. In this study, we quantitatively examine the hypothesis that regional land use/cover change is a contributor to the observed glacier mass loss, taking into account the role of Amazonian biomass burning. We demonstrated here, for the first time, that for tropical Andean glaciers, a massive contribution of black carbon emitted from biomass burning in the Amazon Basin does exist. This is favorable due to its positioning with respect to Amazon Basin fire hot spots and the predominant wind direction during the transition from the dry to wet seasons (Aug-Sep-Oct), when most fire events occur. We investigated changes in Bolivian Zongo Glacier albedo due to impurities on snow, including black carbon surface deposition and its potential for increasing annual glacier melting. We showed that the magnitude of the impact of Amazonian biomass burning depends on the dust content in snow. When high concentration of dust is present (e.g. 100 ppm of dust), the dust absorbs most of the radiation that otherwise would be absorbed by the BC. Our estimations point to a melting factor of 3.3 ± 0.8% for black carbon, and 5.0 ± 1.0% for black carbon in the presence of low dust content (e.g. 10 ppm of dust). For the 2010 hydrological year, we reported an increase in runoff corresponding to 4.5% of the annual discharge during the seasonal peak fire season, which is consistent with our predictions.

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Mass movements and floods triggered by rainstorms are considered some of the most serious environmental problems and are quite often able to cause great disasters in large tropical cities. This has been occurring due to anthropic activities which change natural drainage and stability of slope in urban areas. However, lower monthly rainfalls which occur with high frequency can also cause mass movements and floods. The direct and indirect effects of less intense but continuous rainfall mainly affect less privileged communities, which occupy areas more sensitive to mass movements and flooding, such as locations along river margins, coastal lagoons, mangroves, and steep slopes. This manuscript highlights the important contribution of the lower monthly rainfall totals in triggering mass movements and floods on the east side of Pedra Branca Massif in the city of Rio de Janeiro. Geoprocessing was used to estimate the total monthly rainfall in rain gauges managed by the local authority; create surface interpolation and choropleth maps; and conduct a comparative analysis of histograms of the total monthly rainfall and flooding and mass movement records provided by the City's Civil Defence. The results confirmed the direct relation between higher monthly rainfall totals and mass movements and floods, and also showed that lower monthly rainfall totals can trigger a significant occurrence of such events. Moreover, the monthly rainfall limit that could trigger mass movements and floods was confirmed on the east side of Pedra Branca Massif.