First Red List of Ecosystems assessment of a tropical glacier ecosystem to diagnose the pathways towards imminent collapse


J OS É R. F ERRER -P AR I S * 1 , 2 , 3 ,LUIS D. L LAMBÍ 4 , 5 , ALE JA N D RA MELF O 6 and DAV I D A. KEI TH 1 , 3


Abstract Tropical glaciers are rapidly disappearing, par- ticularly in isolated mountain peaks below 5,000 m eleva- tion. These glaciers are fundamental substrates for unique cryogenic ecosystems in high tropical environments where the ice, melting water and rocky substrate sustain microbio- logical communities and other meso- and macro-biota. This study uses the Red List of Ecosystems guidelines to diagnose the collapse of the tropical glacier ecosystem of the Cordillera deMérida, Venezuela. We undertook the assess- ment with existing estimates of glacier ice extent, indirect historical estimates of ice mass balance and global mechan- istic models of future ice mass balance. We complemented these with additional statistical analysis of trends and biocli- matic suitability modelling to calculate and predict rates of decline and relative severity of degradation in selected eco- system indicators. The evidence suggests an extreme risk of collapse (Critically Endangered) because of a prolonged and acute reduction in ice extent and changes in climatic condi- tions that are leading to the complete loss of ice mass. The ice substrate has declined 90% in the last 20 years, and observed acceleration of the rate of decline suggests it will probably disappear within the next 5 years. Loss of ice substrate will trigger an immediate loss of supraglacial, en- glacial and subglacial biotic compartments and initiate a decades-long succession of forefield vegetation. However, ongoing inventories of native biota and monitoring of eco- system transitions can provide valuable insights and lessons for other ecosystems facing similar risks. The Red List of Ecosystems assessment protocol provides a useful frame- work for comparative analysis of cryogenic ecosystems.


Keywords Climate change, cryogenic biome, forefield biota, glacial biota, ice mass balance, Red List of Ecosystems, risk assessment, tropical Andes


*Corresponding author, j.ferrer@unsw.edu.au 1Centre for EcosystemScience, University of New SouthWales, Sydney, Australia 2UNSW Data Science Hub, University of New South Wales, Sydney, Australia 3IUCN Commission on Ecosystem Management, Gland, Switzerland 4Instituto de Ciencias Ambientales y Ecológicas, Universidad de Los Andes,


Mérida, Venezuela 5Consorcio para el Desarrollo Sostenible de la Ecoregión Andina (CONDESAN),


Quito, Ecuador 6Centro de Física Fundamental, Departamento de Física, Universidad de Los Andes, Mérida, Venezuela


Received 8 June 2023. Revision requested 18 September 2023. Accepted 13 November 2023. First published online 10 September 2024.


The supplementary material for this article is available at doi.org/10.32942/X2VK54


Introduction


spread and intense transformations because of climate change, especially in the tropics (Huss et al., 2017; Masiokas et al., 2020). Tropical glacier ecosystems are re- stricted to the highest elevations of mountain ranges (typic- ally above 4,700 m) where snow and ice have accumulated over years, and the ice, melting water and rocky substrates sustain microbiological communities and other meso- and macro-biota (Hotaling et al., 2017). They are naturally iso- lated and increasingly exposed to rising temperatures and changing precipitation patterns that create an imbalance in ice mass, with more ice lost because of melting and abla- tion than the amount gained by snowfall and rainfall (Sagredo & Lowell, 2012; Rabatel et al., 2013; Veettil & Kamp, 2019). Historical losses of glacial ice mass have been documented in several countries, with .60% having been lost in Colombia and .50% in Peru over the last 60 years (Masiokas et al., 2020). The tropical Andes are consid- ered a global hotspot for cryogenic change (Vuille et al., 2018), having lost over 1 gigatonne of ice during 2000– 2018 (Dussaillant et al., 2019), and the whole tropics region is expected to lose at least 60%of its glacier ice mass by 2100 if current global climate change trends are maintained (Rounce et al., 2023). The functions of glacier ice as a water reservoir, a regula-


C


tor of local temperature and a substrate for biotic processes are being disrupted by continuing losses of mass (Buytaert et al., 2017; Stibal et al., 2020). The changes in biota and eco- system processes associated with glacial retreat will have cas- cading effects as novel ecosystems emerge in recently exposed areas (Llambí et al., 2021; Rosero et al., 2021; Anthelme et al., 2022) and changes in downstream aquatic habitats, biota and water quality affect human livelihoods in the surrounding landscape (Cauvy-Fraunié et al., 2016; Huss et al., 2017; Llambí et al., 2020). Long-term monitoring in the region indicates that plant diversity in the tropical Andes is particularly vulnerable given the high proportion of endemic species that are dependent on low temperatures


This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited. Oryx, 2024, 58(6), 735–745 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323001771


ryogenic ecosystems by definition depend on the dy- namics of snow and ice. They are undergoing wide-


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