Pioneering study analyzes how plant communities throughout the High Andes are responding to climate change

Plant communities in the High Andes face climate change

Climate change is already transforming plant communities across the high Andes. This is the overall conclusion of a study recently published by an international team of ecologists associated with the GLORIA-Andes long-term monitoring network. The study, titled “Changes in the composition of alpine plant communities in the high Andes,” has been recently published in Global Ecology and Biogeography.

Alpine flora is known to be especially sensitive to global warming, with species expected to move to higher elevations as the environment becomes too hot for their optimal development. In this sense, mountains are especially suitable systems for tracing climate-change impacts. However, evidence on climate change-driven shifts of alpine plant communities is based primarily on resurveys of temperate mountain ranges, and significant gaps persist in our understanding of how global warming affects tropical, subtropical and temperate summit plant communities across the Andean range. 

In this context, the GLORIA-Andes Network provides a unique opportunity to assess compositional changes of mountain summit plant communities on a pan-Andean scale. Since 2010, scientists from academic institutions across the six Andean countries have established more than 1300 permanent monitoring plots distributed across 74 summits along the entire mountain range, from the equatorial páramos in the north, to cold steps of Tierra del Fuego in the south (the longest long-term monitoring transect in South America). The Network generates and provides soil temperature data (-10 cm) and dynamics of the vegetation according to protocols established by the global network GLORIA, allowing for comparative analysis at a continental scale.

The study analyzed trends in the GLORIA monitoring summits over 5 to 8 years in various key variables in each permanent plot, such as total vegetation cover (how much terrain is covered by vegetation), and species richness (the number of plant species present). An important concept studied is that of thermal niches, which refers to the optimal temperature range for plant species to occur in any given community. In the analysis, the annual rates of change of these three variables were estimated, and statistical models were used to evaluate their relationship with annual precipitation, the minimum air temperatures of each summit, and the rates of change in the locally recorded soil temperatures (-10 cm).

This article is an abridged version of the original text “Compositional shifts of alpine plant communities across the high Andes” published in Global Ecology and Biogeography, 32(9), under the CC BY-NC-ND 4.0 license in June 2023. Please note that references have been removed. For more detail, full references, and to quote text please use the paper available for download on the right. 

Method: Species richness, vegetation cover and thermal niches

The study used plant community data recorded in 720 permanent plots on 45 mountain summits across the high Andes. The plots were established by the GLORIA-Andes network and are distributed across the entire Andes, from the Cordillera de Mérida in Venezuela (8.8° N) to Tierra del Fuego in Argentina (54° S), spanning a N-S latitudinal gradient of 6870 km and an elevational gradient of nearly 4900 m. Each summit area contains 8 to 16 permanent plots (mode = 16), and data from temperature loggers in the summits allowed an assessment of temporal trends in microclimatic soil conditions. 

Data on plant species richness, their percentage cover, and estimated community-level mean thermal niches of the constituent species (including their thermal optima, minima and niche breath) was collected in two surveys at intervals between 5 and 8 years. The annual rate of changes for these three variables was then estimated, and an analysis based on generalized linear models was used to assess their relationship with annual precipitation, the minimum air temperatures of each summit and rates of change in the locally recorded soil temperatures.

To explore the method in more detail, please refer to page 3 of the paper.

Results: Compositional changes in summit plant communities

The results of the study show that high Andean summits are experiencing heterogeneous changes in temperature and plant community structure. Increases in soil thermal amplitudes (resulting from increased maximum temperatures and decreased minimum temperatures) were the most common pattern across the Andes, but were especially marked in the Patagonia and Puna summits. The majority of summits showed an increase in vegetation cover and species richness, but the highest summits lost plant cover (subnival and nival summits) and species numbers decreased (nival summits), especially in the northern páramos, where endemic species were particularly affected. In addition, most plant communities experienced changes in their composition: an increase of plant species with broader thermal niches (i.e. species typical of lower elevations capable of surviving in a greater range of temperatures) and higher optima (i.e. species capable of thriving in a warmer environment).

The observed shifts indicate a heightened susceptibility of high Andean vegetation to the impacts of climate change. Across most summits, particularly those at lower elevations, there is a discernible increase in plant cover and species diversity, driven by the increasing prominence of species that thrive in warmer climates and typically hail from lower altitudes. However, summits from higher elevations are experiencing a decline in vegetation cover and species richness. Moreover, high mountain endemics are diminishing their cover, especially in tropical summits near the equator. To gain a deeper understanding of the relationship between these changes and climate warming, as well as alterations in precipitation patterns, the researchers underscore the necessity of maintaining sustained monitoring efforts over an extended period. This study encompasses data spanning 2012 to 2019, and the observed trends still exhibit considerable variability across the diverse regions under study.

In addition to providing essential baseline data for biodiversity conservation and adaptation management in the Andes, this publication highlights the importance of South-South cooperation in the task of quantifying and monitoring the effects of climate change at a continental scale. Studies like this are useful to scientists, conservation managers and decision makers around the world, in their task of responding in an informed manner to the impacts of climate change on mountain ecosystems.

Further resources

• Suggested Citation:Cuesta, F., Carilla, J., LLambí, L. D., Muriel, P., Lencinas, M. V., Meneses, R. I., Feeley, K. J., Pauli, H., Aguirre, N., Beck, S., Bernardi, A., Cuello, S., Duchicela, S. A., Eguiguren, P., Gamez, L. E., Halloy, S., Hudson, L., Jaramillo, R., Peri, P. L. … Tovar, C. (2023). Compositional shifts of alpine plant communities across the high Andes. Global Ecology and Biogeography, 00, 1–16. https://doi. org/10.1111/geb.13721