By José R. Ferrer-Paris, Luis Daniel Llambí and Alejandra Melfo, 11th September 2024
When we think of tropical landscapes, ice and snow do not usually come to mind. Yet tropical glaciers do exist, and they are fascinating, remote and dynamic ecosystems. Found only at the highest elevations in equatorial latitudes, they emerge like frozen islands from the hot and humid landscape surrounding them. Their icy substrate depends entirely on a delicate balance of precipitation, temperature, radiation and wind. Like any place of extreme conditions, it is a harsh environment, yet life persists in diverse forms—from specialized bacteria to microscopic algae and mesoscale invertebrates—drawing sustenance from sunlight and windfall, defying freezing temperatures with remarkable adaptations and flowing downwards and onwards with the water and the wind.
In Venezuela, northern South America, seasonal snow and permanent glaciers in the high altitudes of the Cordillera de Mérida have inspired poets and painters for centuries. This region is known as the ‘Sierra Nevada’ of Mérida, or by the popular name of ‘the land of the eternal snow’. Yet what once seemed stable and eternal now appears increasingly fragile and ephemeral. Today, the old names referring to everlasting ice and snow remain in our memories, pictures and maps, but most of the white caps of the Cordillera are already gone, and those that still remain are rapidly vanishing.
Left: Painting from 1844 by Ferdinand Konrad Bellermann: ‘Die Sierra Nevada bei Mérida, vorn eine Hütte’. Credit: Kupferstichkabinett, Staatliche Museen zu Berlin/Atelier Schneider; CC BY-NC-SA. Right: Venezuelan Postcard from 1950. Photo: Public Domain; getarchive.
There are thousands of tropical glaciers around the world, but with global temperatures continuing to rise, their future is uncertain. For years, researchers have been studying various aspects of glacier ice dynamics: geological evidence of their past, remote sensing of the ice surface, and mass balance models projecting changes in ice volume into the future. There is also increasing interest in understanding the dynamics and composition of their unique but often neglected microbiota, and the colonization by vascular plants and development of novel ecosystems after glaciers retreat. But how does all this information fit together to reveal the bigger picture of the processes affecting tropical glaciers in a warming world?
The Humboldt Glacier in August 2022 (left) and December 2023 (right). Photos: Jordy Alce González (left) & Stefano Pozzebon (right).
To quantify the decline and probability of collapse of these increasingly fragile ecosystems, we propose using a risk assessment framework. The IUCN Red List of Ecosystems provides a tool for assessing and monitoring the status of ecosystems, by evaluating their health and the threat levels they face, and identifying effective management strategies to reduce the loss of biodiversity. It has been applied to several terrestrial, freshwater and marine ecosystems, but can also be useful for exploring the risk of collapse in the cryogenic biome (ecosystems dominated by ice and snow), which is often underrepresented in national assessments.
Field and lab work with the microbiota of the glacier ice, December 2023. Photos: Stefano Pozzebon.
We completed the first Red List of Ecosystems assessment of a tropical glacier ecosystem, using the IUCN guidelines to assess the status of the Cordillera de Mérida in Sierra Nevada National Park, Venezuela. The process of describing the ecosystem and proposing a conceptual ecosystem model enabled us to better understand the connections between its different biotic and abiotic elements. To establish a comprehensive picture, we combined data from a broad range of sources: we took samples and made observations in the field, reviewed the existing literature, explored cartographic reconstruction, built ecological models based on remote sensing and climatic data, and carried out sophisticated statistical analysis. This approach enabled us to assess the ecosystem’s exposure to threats, predict rates of its decline and calculate the relative severity of degradation affecting this unique landscape.
The result of these analyses is sobering: our assessment suggests that the tropical glaciers of the Cordillera de Mérida are Critically Endangered, with an imminent risk of collapse. The Sierra Nevada of Mérida has lost most of its glaciers, and we are most likely witnessing the final days of the last remaining glacier, on Peak Humboldt.
Fieldwork to examine the vegetation succession in the glacier forefield, December 2023. Photos: Stefano Pozzebon.
Sadly, last-minute efforts to avoid complete melting of the Humboldt glacier are unlikely to counteract the dramatic force of climate change. In the most recent visit by a research team in December 2023, the extent of the glacier ice was estimated to be just 2 hectares—a 50% reduction from 2019 and less than 1% of the extent in 1952 (estimated from aerial photographs). Although it is probably too late to save this glacier from disappearing, we must try and learn as much as possible from it while it is still there. Research into the microbiota around the last remnant of ice—and into the inevitable transformation of the glacier forefield into a novel ecosystem—is underway, and this work will hopefully reveal useful insights and provide lessons for other ecosystems facing similar risks, helping us to avoid a future without these special areas of tropical mountains covered in eternal snow.
The article ‘First Red List of Ecosystems assessment of a tropical glacier ecosystem to diagnose the pathways towards imminent collapse’ is available open access in Oryx—The International Journal of Conservation.
