“Tropical glaciers” may sound to some like a contradiction in terms. Yet these glaciers are very real, existing in mountainous tropical and subtropical regions of Africa, Indonesia, and South America and providing much-needed water to more than one sixth of the world’s population. More specifically, they play crucial roles in moderating seasonal variations in the flows of mountain rivers and ensuring steady supplies of freshwater to communities downstream for drinking, agriculture, and other uses.
However, climate change is shrinking glaciers worldwide and increasingly putting water security at risk in tropical and subtropical regions that depend on glaciers. The substantial socioeconomic vulnerabilities of many of the people affected only exacerbate problems of water security.
Rapidly receding tropical glaciers are also contributing to landscape changes at historically unprecedented rates—and not all of these changes are benign. For instance, newly exposed slopes and natural dams are often unstable and susceptible to failure, potentially leading to avalanches, landslides, or glacier lake outburst floods. Shrinking glaciers may also reveal new glacial lakes and release sediment into valleys, changes that could benefit downstream communities by providing natural reservoirs but that could also compromise water quality [López-Moreno et al., 2017].
Understanding the ongoing evolution of these distinctive environments as well as current and potential future threats posed to people is vital for maintaining the security and ways of life of vulnerable populations. Socioeconomic conditions, demography, environmental history, government policies, and cultural beliefs all influence vulnerability in tropical mountain environments. Given this complexity, measures to adapt to and mitigate effects of dwindling tropical glaciers should be based on multidimensional and interdisciplinary strategies for research and resource management.
Below we describe research efforts making use of traditional and innovative survey methods to study glacier retreat and dynamics in the Andes—home to roughly 95% of the world’s tropical glaciers—and discuss why continuing these efforts is so important, with a specific focus on Peru.
A Rich Source of Services Under Threat
Communities the world over, including in the tropical Andes, value dynamic mountain ecosystems, which host a diversity of endemic species and often embody the ancestral knowledges of Indigenous Peoples. These ecosystems also offer important ecosystem services, such as regulating hydrological processes, sequestering carbon, and improving water quality. For people downstream, they also provide food, power, and water for drinking and irrigation, as well as aesthetic and recreational value.
Mountain ecosystems, no matter where they are located, are vulnerable to natural and anthropogenic threats, including soil erosion and degradation, changes in land use, and overexploitation of resources. Each of these threats, in turn, affects hydrological performance (e.g., increased water turbidity caused by soil erosion), water quality, streamflow availability, and hillslope stability in these systems [Patiño et al., 2021; Karpouzoglou et al., 2020]. However, the effects of climate change on mountain environments prone to degradation disproportionately fall on populations relying on tropical glaciers in the Global South, where many people have limited economic resources, especially those who get most of their income from agriculture and raising livestock.
Currently, Andean communities face a multitude of intertwined challenges related to climate change [Bradley et al., 2006; Chevallier et al., 2011]. These challenges include increasing water and energy demands and diminishing and degraded wetlands at a time when warming temperatures are shrinking glaciers and affecting the long-term availability of water runoff. Regional volcanism and even wildfires in the Amazon, which deposit small rock fragments and dark, sunlight-absorbing particulates onto glacial surfaces, amplify glacier responses to warming and enhance retreat rates [Brock et al., 2007]. The effects of this retreat are especially severe in areas that are highly dependent on summer meltwater runoff [Moreiras, 2005].
Not only is the availability of water supply being affected, but also the chemistry—and quality—of the water supply is changing. For example, in the Cordillera Blanca mountains, a part of the Andes located in Peru, soil erosion and glacier meltwater contribute to total runoff, increasing the delivery downstream of sediments containing heavy metals [López-Moreno et al., 2017]. Moreover, other natural ecosystem services are being disrupted by factors including the displacement of ice divides (the highest part of a glacier, which separates and guides water flows in different directions), lake expansion, species migration, and biogeochemical changes brought about by changes in water quality. Compromised ecosystem services include biodiversity, erosion and inundation control, and flood attenuation.
Rapid melting of glacier ice and snow is also increasing the frequency and range of hazards—from glacial lake outburst floods to landslides, debris flows, and rock or glacier ice avalanches—facing human settlements [Cook et al., 2016; Dyurgerov and Meier, 2005]. For example, once they are free of ice, the rocky moraine dams that hold back glacial lakes can erode and eventually fail, either gradually as water pressure and weathering take their toll or suddenly, with little to no warning. In 1941, a chunk of an adjacent glacier fell into glacial Lake Palcacocha in the Andes near the city of Huaraz, Peru. The moraine wall containing the lake failed, releasing a mudslide downhill. Within 15 minutes, the mudslide, carrying ice and rock boulders, buried parts of Huaraz. More than 1,800 people died as a result [Wegner, 2014].
With so many changes occurring and challenges emerging, in the Andes and elsewhere, it is becoming increasingly critical to understand mechanisms and rates of glacier recession in tropical mountain environments and, even more important, how these recessions are affecting human communities that rely upon glaciers and mountain ecosystems [Ceballos et al., 2006; Rabatel et al., 2018].
A Multitude of Efforts
At a 2019 workshop, an international group of researchers gathered to discuss challenges and opportunities in mountain socioenvironmental systems and share experiences from a variety of research efforts that highlight the importance of understanding how not only long-term climate change but also seasonal climate variability relate to glacier changes and human impacts in Peru. This understanding can help improve predictions of vegetation changes and weather patterns relevant to humans, addressing, for example, the potential effects of El Niño or extreme cold events in high Andean ecosystems.
In 2011, institutions including the Instituto Nacional de Investigación en Glaciares y Ecosistemas de Montaña and the Servicio Nacional de Meteorología e Hidrología del Perú began to monitor precipitation and humidity in glacierized regions of Peru by installing weather stations, for example, at Quisoquipina and Suyuparina glaciers in Cusco and at Coropuna Glacier in Arequipa. The data they have gathered reveal the seasons in which the contributions of ice melting are most important in the management of water resources considering the responses of these glaciers to different climatic conditions.
In the Peruvian Andes, water availability is very sensitive to climate variability as well as to geographic variability. For instance, some areas at higher elevations store glacial lakes that serve as reservoirs, in contrast to some lower-elevation environments where water sources are less abundant. The Instituto Nacional de Innovación Agraria has begun modeling the principal maize varieties grown under different climatic conditions in Peru’s coastal regions and in the Andean highlands—where both temperature and precipitation affect the crop cycle and vary grain yields—helping inform how crop failures may be avoided under future conditions of water scarcity driven by reduced glacial runoff.
In addition, the Smithsonian Conservation Biology Institute, in collaboration with Agricola Arzu, a Peru-based agriculture company, has assessed how spatiotemporal variation in grassland plant community composition correlates with climate variables at high elevations (3,800–4,500 meters above sea level). Among other results, this work helps improve the predictability of vegetation changes due to glacier changes or extreme events in high Andean environments.
Recent interventions in the management of Andean watersheds have been initiated to conserve and restore the bofedales, highland wetlands characterized by their organic-rich soils and water storage capacity. These wetlands cover only 0.42% of the total land area in Peru, but they are distributed in almost all regions of the country and work as important sponges to store water and sequester carbon, improve water quality, and deliver flows during the dry season. The bofedales have been heavily degraded by anthropogenic activities like cattle ranching, agriculture, and water extractions, which reduce water storage, carbon sequestration, and vegetation cover. Furthermore, as water in the bofedales largely derives from glacial sources, they are sensitive to glacier retreat.
One such initiative is the Natural Infrastructure for Water Security project, which aims to restore highland environments and their ecosystem services through the implementation of natural infrastructure. Another is the creation of conservation areas by the National Service of Natural Areas Protected by the State, such as the Regional Conservation Area of Ausangate, which involves the development of environmental monitoring plans. Unfortunately, the possibility of a delay between intervention efforts and visible improvements in bofedal water levels, predicted by theoretical studies and considering time lags in the effects of climate change, complicates efforts to understand the natural and anthropogenic drivers that influence these ecosystems. Therefore, both short- and long-term monitoring plans are needed to assess landscape configurations and the effectiveness of these interventions.
Researchers have also identified a need to characterize the socioecosystems of Andean environments more comprehensively—that is, to better understand the coupling between local communities and their natural surroundings with regard to climate change adaptation and resilience [Mathez-Stiefel et al., 2017; Sylvester et al., 2017]. This improved understanding will help researchers evaluate local management tools for climate change adaptation and community-based adaptation initiatives, so that these efforts can be complemented or revised to promote long-term preservation of critical tropical mountain glaciers and ecosystems.
Bridging Science and Policy
How can researchers work together at the science-policy interface to achieve sustainable water management in mountain environments? And what science-based evidence is required for risk assessment and management in these environments? The international Water Security and Climate Change Adaptation in Peruvian Glacier-fed River Basins project, which also goes by the name RAHU (the Quechua word for “snowy mountain”), is tackling these difficult questions.
RAHU is developing an approach that integrates glacier and water security assessments to transform understanding of how shrinking glaciers and current water usage affect human vulnerability among Andean communities. Their approach combines two elements. A physical glacier surface energy balance model enables realistic representations of glacier dynamics in glacier melt projections. Meanwhile, mapping human water use at high spatiotemporal resolution enables assessments of current levels of water security (or insecurity) and predictions of future levels. This project also evaluates the scientific, policy, and operational considerations of local climate change adaptation strategies and supports the implementation of such strategies.
Another project, Producing Energy and Preventing Hazards from Surface Water Storage in Peru, or PEGASUS, aims to characterize changing sediment dynamics in mountain environments resulting from deglaciation. In particular, the project is examining the role of glacial lakes in removing and storing sediment from erosion-prone glacierized slopes upstream of the lakes, as well as the impacts of mobilized sediment on downstream water quality and critical hydropower infrastructure.
Cultural and Historical Considerations
The Andes and their glaciers not only provide freshwater resources and serve as climate change indicators, but also they underpin the cultural identities and practices of Indigenous communities. Today, however, some of these communities are threatened by anthropogenically induced changes.
Researchers from the Bosques Andinos program advocate that historical boundaries and infrastructures of Indigenous territories should be preserved as a means both to maintain the cultural integrity of these communities and to mitigate effects of climate change on the landscape (e.g., soil erosion) that are exacerbated by development.
In the Ausangate area of the Vilcanota Range in Cusco, Peru, Quechua communities have managed and transformed the landscape for centuries through their agricultural and livestock grazing practices. However, in recent years, those communities have struggled with rapid changes in their lands, including the loss of bofedales, reduction in soil fertility, and water and soil contamination. These changes have been caused by overgrazing, construction of roads and dams, peat digging, urban development, energy generation, mining operations, and other pressures—in addition to climate change. Even though methodologies to assess the impacts of these practices are already known, much less is known about how these communities perceive these changes to their territory.
Therefore, research is needed to better understand the perceptions and vulnerabilities of Andean communities regarding water security and adaptation to climate change. Their perspectives can then be incorporated to inform water resources management and risk mitigation strategies.
An Integrated Approach to Adaptation
An overarching message that emerged from the 2019 workshop was that holistically understanding ongoing changes to tropical mountain glaciers and their surrounding environments, and current and future impacts on the people that depend on those environments, requires interdisciplinary approaches to developing feasible, effective, and acceptable adaptation and mitigation measures (Figure 1). Thus, future research and resource and risk management efforts for glacierized regions should integrate input from scientists and policy specialists as well as socioeconomic and cultural considerations of affected communities.
The authors thank the Mountain Research Initiative (MRI) for sponsoring the workshop under the MRI Synthesis Workshop 2019 program, and acknowledge the partial support from Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT) and the Newton-Paulet Fund through grants 009-2019 and 005-2019 – FONDECYT/CONCYTEC and the Gordon and Betty Moore Foundation through grant 7711. Thanks are also owed to the assistants from the Centro de Investigación y Tecnología del Agua for helping with the event coordination and logistics and sharing photographs of Lake Sibinacocha and its bofedales. The authors also acknowledge Adrián Ccahuana for sharing the Ausangate Glacier photography.
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Tania V. Rojas (email@example.com), Department of Engineering, Pontificia Universidad Católica del Perú, Lima; also at Red Yaku, Lima; formerly at Centro de Investigación y Tecnología del Agua (CITA), Universidad de Ingenieria y Tecnologia (UTEC), Lima; Duncan Quincey, School of Geography, University of Leeds, Leeds, U.K.; Pedro Rau and Daniel Horna-Muñoz, CITA, UTEC, Lima; and Jorge D. Abad, Red Yaku, Lima