When I wrote my anthropology capstone, I focused on how Quechua communities in the Cordillera Vilcanota interpret and adapt to climate change. The fact that climate change is happening was treated as background. In this post I want to flip the focus and put the evidence in the foreground.
The Cordillera Vilcanota sits in southeastern Peru. It holds the world’s largest tropical ice cap, the Quelccaya, and one of the largest high-altitude lakes on the planet, Laguna Sibinacocha. It is also a headwater region for the Amazon. That makes it a place where the science of climate change is unusually concentrated. There is a long, well-documented record of what is happening to the ice, the water, and the living systems that depend on both.
Here is what the published research says, organized around three questions.
1. What is happening to the ice?
Glaciers are blunt indicators. They grow when conditions are cold and wet enough, and they shrink when they are not. In the Cordillera Vilcanota, they are shrinking, and they have been shrinking faster over time.
Hanshaw and Bookhagen (2014) used 158 satellite images covering 1975 to 2012 and found that the glaciated area of the Cordillera Vilcanota has been declining at about 4 km² per year since 1988. The Quelccaya Ice Cap alone has been losing about 0.57 km² per year since 1980. The rate of loss in the 2000s was about 13% higher than in the 1990s. The trend is not just down. It is also speeding up.
Drenkhan et al. (2018) zoomed out to the larger Vilcanota-Urubamba basin and found that total glacier area dropped from 226 km² in 1988 to 142 km² in 2016. That is a 37% loss in less than three decades. Their projections, which span the range of possible emissions futures, suggest the basin could lose between 41% and 93% of its remaining glacier area by the end of this century.
A more recent local study by Montoya-Jara et al. (2024) measured two specific glaciers in the range, Quisoquipina and Suyuparina, using a combination of satellite and LIDAR data. Between 1990 and 2013, Quisoquipina lost about 12% of its area and Suyuparina lost about 22%. Suyuparina has since become the focus of work by King et al. (2025), who showed that the glacier’s mass loss rate from 2016 to 2024 was more than double the long-term average dating back to 1977. The mechanism they identified is a feedback loop involving ice cliffs and meltwater ponds on the glacier surface, which absorb more solar radiation and accelerate melt.
The pattern is consistent across studies, instruments, and time scales. The ice is going.
2. What is happening to the water?
When glaciers shrink, the water cycle does not just lose volume. It changes shape.
Mendoza Villavicencio et al. (2021) tracked snow cover in the Sibinacocha watershed from 1984 to 2019 using Landsat imagery. They found a 26% decline over that period and confirmed an inverse relationship with rising temperatures. Less snow now means less recharge of streams later.
Below the glaciers, the lakes are also changing. Sae-Lim et al. (2025) modeled the energy balance of Laguna Sibinacocha and projected the lake to warm by between 2.5 and 5.9°C by the end of this century. That is a remarkable amount of warming for a body of water sitting at 4,870 meters of elevation.
The dry-season water that flows out of these systems comes from two main sources. One is glacier melt, which is already declining as the glaciers shrink. The other is bofedales, which are peat-rich high-altitude wetlands that act as natural sponges. Gribbin et al. (2024) studied a Vilcanota headwater catchment during the 2022 dry season and measured both. They found that the contribution from glaciers in the river they studied dropped roughly in half over the dry season, while the bofedales kept delivering steady flow.
This matters for two reasons. First, it tells us that the wetlands are already doing important work to buffer downstream water supply. Second, it tells us they will become more important as the glaciers shrink further. If the bofedales degrade, there is no Plan B.
Human water management is already changing the system as well. Bello et al. (2023) showed that the dam at Sibinacocha, in operation since 1988 to feed the Machupicchu hydropower plant, has created roughly a 20% water deficit during the wet season and a 30% surplus during the dry season relative to the natural flow. That is good for hydropower and for downstream supply. It is also a significant alteration of the river ecology, which depends on natural seasonal cycles.
3. What is happening to the living systems?
Some of the most striking evidence comes from the things that live there.
Seimon et al. (2017) reported on a decade of monitoring three species of high-altitude frogs in the Vilcanota. The frogs are now found at elevations between 5,200 and 5,400 meters, among the highest amphibian populations on Earth. They have moved upslope into ponds that did not exist before, formed in the spaces left by retreating glaciers. The team also documented that one corridor between two retreating glaciers widened by an average of 18.4 meters per year between 2005 and 2015.
Reider et al. (2024) studied the soil left behind when glaciers pull back. Normally, that soil stays nearly lifeless for over a century before plants can colonize it, because there is almost no nitrogen, no organic matter, and no water-holding capacity. They found that wild vicuñas, which are native Andean camelids, are creating shortcut nutrient hotspots by using specific patches of new ground as communal latrines. Soils enriched by camelid dung had organic matter, moisture, and microbial life at levels orders of magnitude higher than the surrounding moraine. The animals are essentially fertilizing the future ecosystem and shaving more than a century off the timeline of recovery.
These two findings sit in tension with each other. Frogs and camelids are responding to deglaciation in ways that look adaptive. At the same time, the chytrid fungus continues to circulate in amphibian populations, the pace of habitat change is accelerating, and the new ecosystems forming on these landscapes are emerging into conditions very different from the ones the existing species evolved in.
The longer view
The recent satellite record makes the present picture clear, but the deeper time record is also informative.
Michelutti et al. (2019) analyzed sediment from inside a pre-Inca ceramic pot recovered from underwater ruins in Laguna Sibinacocha. The pot was originally placed on dry land. Radiocarbon dating of its sediment showed that the lake rose and submerged it in the late 1600s CE. That timing followed a documented wet period beginning around 1520 CE. The value of this study is not the date of the flooding. It is the demonstration that the region’s climate is capable of producing persistent state shifts. The hydrology of these mountains is not always slow and steady. It can change and stay changed.
Perez and Loisel (2023) extended that view further. By comparing peat cores from across the high Andes, including a new one from the Alta Murmurani peatland in the Vilcanota, they reconstructed climate conditions over thousands of years. Their conclusion was that the wettest, most peat-forming periods correspond to specific moments of climate transition rather than to long stable averages. Climate transitions are when the landscape changes the most.
That paleoclimate record is a useful frame for what we are seeing now. The Cordillera Vilcanota is once again in a transition. The ice is retreating. The lakes are warming. The wetlands and the species that depend on them are being reorganized. The instruments are different from those of the past, but the kind of thing happening is not unprecedented.
What is unprecedented is the speed.
Why this matters
If you put all of this evidence together, the picture is consistent across more than a dozen independent studies. The Cordillera Vilcanota is losing its ice. The water systems below are changing in measurable ways. The species and ecosystems are shifting in response. The pace of change is accelerating, and the projections for the rest of this century are wide-ranging but not optimistic.
This region is also a window onto something larger. The tropical Andes are home to most of the world’s tropical glaciers, and they sit at the intersection of three things at once. They are highly sensitive to small atmospheric shifts. They support hundreds of thousands of downstream people. They are studied closely enough that we can actually measure what is happening.
In the next decades, what is documented here will keep informing how we understand the climate system as a whole. It will also keep mattering, every dry season, to the communities living in its shadow.
References
Bello, C., Suarez, W., Drenkhan, F., & Vega-Jácome, F. (2023). Hydrological impacts of dam regulation for hydropower production: The case of Lake Sibinacocha, Southern Peru. Journal of Hydrology: Regional Studies, 46, 101319. https://doi.org/10.1016/j.ejrh.2023.101319
Drenkhan, F., Guardamino, L., Huggel, C., & Frey, H. (2018). Current and future glacier and lake assessment in the deglaciating Vilcanota-Urubamba basin, Peruvian Andes. Global and Planetary Change, 169, 105-118. https://doi.org/10.1016/j.gloplacha.2018.07.005
Gribbin, T., Mackay, J. D., MacDonald, A., Hannah, D. M., Buytaert, W., Baiker, J. R., Montoya, N., Perry, L. B., Seimon, A., Rado, M., Arias, S., & Vargas, M. (2024). Bofedal wetland and glacial melt contributions to dry season streamflow in a high-Andean headwater watershed. Hydrological Processes, 38(7), e15237. https://doi.org/10.1002/hyp.15237
Hanshaw, M. N., & Bookhagen, B. (2014). Glacial areas, lake areas, and snow lines from 1975 to 2012: Status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru. The Cryosphere, 8(2), 359-376. https://doi.org/10.5194/tc-8-359-2014
King, O., et al. (2025). The impact of supraglacial ice cliff and pond formation on debris-free, tropical glacier mass loss. Journal of Glaciology. https://doi.org/10.1017/jog.2025.10109
Mendoza Villavicencio, L. M., Mendes, D., Mendes da Silva, G. A., Monteiro, F. F., & Andrade, L. D. M. B. (2021). Snow cover area analysis and its relation with the temperature in Sibinacocha Lake watershed, Peru, during 1984-2019 using Landsat and ERA5 data. Remote Sensing Letters, 12(4), 353-363. https://doi.org/10.1080/2150704X.2020.1868603
Michelutti, N., Sowell, P., Tapia, P. M., Grooms, C., Polo, M., Gambetta, A., Ausejo, C., & Smol, J. P. (2019). A pre-Inca pot from underwater ruins discovered in an Andean lake provides a sedimentary record of marked hydrological change. Scientific Reports, 9, 19193. https://doi.org/10.1038/s41598-019-55422-1
Montoya-Jara, N., Loayza, H., Gutiérrez-Rosales, R. O., Bueno, M., & Quiroz, R. (2024). Estimation of glacier outline and volume changes in the Vilcanota Range snow-capped mountains, Peru, using temporal series of Landsat and a combination of satellite radar and aerial LIDAR images. Remote Sensing, 16(20), 3901. https://doi.org/10.3390/rs16203901
Perez, N., & Loisel, J. (2023). Synthesis of high-Andean peat cores reveals suite of Holocene climate conditions favorable for peat formation. Quaternary Science Reviews, 322, 108413. https://doi.org/10.1016/j.quascirev.2023.108413
Reider, K. E., Bueno de Mesquita, C. P., Anderson, K., Quispe Pilco, R., Luza Victorio, M. A., Gelona III, A. R., & Schmidt, S. K. (2024). Wild Andean camelids promote rapid ecosystem development after glacier retreat. Scientific Reports, 14, 31913. https://doi.org/10.1038/s41598-024-83457-6
Sae-Lim, J., et al. (2025). Lake energy balance response to 21st century warming in the tropical high Andes.
Seimon, T. A., Seimon, A., Yager, K., Reider, K., Delgado, A., Sowell, P., Tupayachi, A., Konecky, B., McAloose, D., & Halloy, S. (2017). Long-term monitoring of tropical alpine habitat change, Andean anurans, and chytrid fungus in the Cordillera Vilcanota, Peru: Results from a decade of study. Ecology and Evolution, 7(5), 1527-1540. https://doi.org/10.1002/ece3.2779