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1. Pastoralism in the high tropical Andes: A review of the effect of grazing intensity on plant diversity and ecosystem services

   https://doi.org/10.1111/avsc.12791  

   Duchicela, Sisimac Alli; Llambí, Luis Daniel; Bonnesoeur, Vivien; Román‐Dañobeytia, Francisco (July 2024, Applied Vegetation Science)

   Durigan, Giselda (Ed.)

   Pastoralism is a land‐use system that involves the care and use of grazing livestock and has been more common in areas of low resource availability. In this review, we analyze the impact of pastoralism on biodiversity and ecosystem services across the tropical Andes. This region is the most extensive and populated tropical mountain region in the world and presents a high diversity of biomes, livestock types and management histories. Given that pastoralism is a main land use here, understanding its impacts is important for providing appropriate recommendations for sustainable management. LocationTropical Andes; Venezuela to the north of Argentina and Chile. MethodsTo understand these impacts, we performed a systematic literature search (August 2021) and obtained 103 articles. We created a conceptual framework to map how available research has contributed to our understanding of the main pastoral systems, their associated management strategies and the impact of different grazing intensities on vegetation cover/diversity and ecosystem services. ResultsWe found that research has focused on two leading pastoral systems in the region: bovines in the páramo biome of the northern Andes and camelids in the puna biome of the central Andes. We found important environmental impacts at high grazing intensities for both the puna camelid and páramo bovine pastoral systems, including a decrease in soil organic carbon and an increase in soil compaction, a decrease in above‐ground biomass, plant species richness, and graminoid cover, as well as clear changes in the growth‐form composition of vegetation. ConclusionsGiven these findings, we recommend coordinated research efforts using common methodologies, documenting current and previous land use, including stocking rates, and combining observational and experimental approaches to develop a more integrated understanding of pastoralism's impacts across this diverse and vulnerable region. 

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2. Herbarium specimens reveal a constrained seasonal climate niche despite diverged annual climates across a wildflower clade

   https://doi.org/10.1073/pnas.2503670122  

   Bontrager, Megan; Worthy, Samantha J; Cacho, N Ivalú; Leventhal, Laura; Maloof, Julin N; Gremer, Jennifer R; Schmitt, Johanna; Strauss, Sharon Y (July 2025, Proceedings of the National Academy of Sciences)

   Quantifying species’ niches across a clade reveals how environmental tolerances evolve, and offers insights into present and future distributions. We use herbarium specimens to explore climate niche evolution across 14 annual species of theStreptanthus(s.l.) clade (Brassicaceae), which originated in deserts and diversified into cooler, moister areas. To understand how climate niches evolved, we used historical climate records to estimate each species’ 1) classic annual climate niche, averaged over specimen collection sites; 2) growing season niche, from estimated specimen germination date to collection date, averaged across specimens (specimen-specific niche); and 3) standardized seasonal niche based on average growing seasons of all species (clade-seasonal niche). In addition to estimating how phenological variation maps onto climate niche evolution, we explored how spatial refugia shape the climate experienced by species by 1) analyzing how field soil texture changes relative to the climate space that species occupy and 2) comparing soil water holding capacity from each specimen locality to that of surrounding areas. Specimen-specific niches exhibited less clade-wide variation in climatic water deficit (CWD) than did annual or clade-seasonal niches, and specimen-specific temperature niches showed no phylogenetic signal, in contrast to annual and clade-seasonal temperature niches. Species occupying cooler regions tracked hotter and drier climates by growing later into the summer, and by inhabiting refugia on drought-prone soils. These results underscore how phenological shifts, spatial refugia, and germination timing shape “lived” climate. Despite occupying a large range of annual climates, we found these species are constrained in the conditions under which they thrive. 

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3. Paleo- ecosystem, climate and fire dynamics during the Late Miocene-Pliocene in Northwest Argentina

   https://doi.org/10.1016/j.palaeo.2026.114097  

   Ghosh, Adit; Cotton, Jennifer M; Hauswirth, Scott C; Hyland, Ethan G; Azmi, Iffat; Tineo, David; Raigemborn, M Sol; Insel, Nadja (October 2026, Palaeogeography, Palaeoclimatology, Palaeoecology)

   The response of vegetation and fire to sub-million-year changes in climate informs our understanding of how modern ecosystems evolved, especially in understudied regions such as the South-Central Andes. We use multiproxy analysis of fossil soils (paleosols) in the Río Iruya Canyon of northwest Argentina to investigate changes in vegetation and fire activity, and how these responded to a changing hydroclimate in a tectonically active region. We analyze carbon isotopic composition of soil bulk organic matter as a proxy for C4 vegetation, phytoliths as proxies for forest and grass abundance, polycyclic aromatic hydrocarbons as a proxy for fire activity and angiosperm and gymnosperm abundance, and bulk elemental geochemistry of paleosols as a proxy for mean annual precipitation and temperature. C4 vegetation appeared at Río Iruya by 6.6 Ma but remained scarce throughout the investigated interval, while vegetation alternated between periods of increased gymnosperm and angiosperm cover. We find no relationship between C4 vegetation and fire activity, likely owing to this C4 vegetation scarcity. Near-modern average precipitation values are noted through the Late Miocene–Pliocene, with precipitation appearing to be the primary control on both vegetation distribution and fire regimes, with drier periods showing reduced fire activity and enhanced gymnosperm cover. C4 grass distribution, however, does not change appreciably with these hydroclimatic fluctuations. Our results suggest that changes in precipitation due to regional climate change can drive changes in fire and vegetation dynamics but may not have led to C4 dominance in central South America. 

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4. Tundra vegetation change and impacts on permafrost

   https://doi.org/10.1038/ s43017-021-00233-0  

   Monique M. P. D. Heijmans; Rúna Í. Magnússon; Mark J. Lara; Gerald V. Frost; Isla H. Myers-Smith; Jacobus van Huissteden; M. Torre Jorgenson; Alexander N. Fedorov; Howard E. Epstein; David M. Lawrence; et al (January 2022, Nature reviews)

   Tundra vegetation productivity and composition are responding rapidly to climatic changes in the Arctic. These changes can, in turn, mitigate or amplify permafrost thaw. In this Review, we synthesize remotely sensed and field-observed vegetation change across the tundra biome, and outline how these shifts could influence permafrost thaw. Permafrost ice content appears to be an important control on local vegetation changes; woody vegetation generally increases in ice-poor uplands, whereas replacement of woody vegetation by (aquatic) graminoids following abrupt permafrost thaw is more frequent in ice-rich Arctic lowlands. These locally observed vegetation changes contribute to regional satellite-observed greening trends, although the interpretation of greening and browning is complicated. Increases in vegetation cover and height generally mitigate permafrost thaw in summer, yet, increase annual soil temperatures through snow-related winter soil warming effects. Strong vegetation–soil feedbacks currently alleviate the consequences of thaw-related disturbances. However, if the increasing scale and frequency of disturbances in a warming Arctic exceeds the capacity for vegetation and permafrost recovery, changes to Arctic ecosystems could be irreversible. To better disentangle vegetation– soil– permafrost interactions, ecological field studies remain crucial, but require better integration with geophysical assessments. 

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5. From past habitats to present threats: tracing North American weasel distributions through a century of climate and land use change

   https://doi.org/10.1007/s10980-024-01902-3  

   Cheeseman, Amanda E; Jachowski, David S; Kays, Roland (May 2024, Landscape Ecology)

   Abstract ContextShifts in climate and land use have dramatically reshaped ecosystems, impacting the distribution and status of wildlife populations. For many species, data gaps limit inference regarding population trends and links to environmental change. This deficiency hinders our ability to enact meaningful conservation measures to protect at risk species. ObjectivesWe investigated historical drivers of environmental niche change for three North American weasel species (American ermine, least weasel, and long-tailed weasel) to understand their response to environmental change. MethodsUsing species occurrence records and corresponding environmental data, we developed species-specific environmental niche models for the contiguous United States (1938–2021). We generated annual hindcasted predictions of the species’ environmental niche, assessing changes in distribution, area, and fragmentation in response to environmental change. ResultsWe identified a 54% decline in suitable habitat alongside high levels of fragmentation for least weasels and region-specific trends for American ermine and long-tailed weasels; declines in the West and increased suitability in the East. Climate and land use were important predictors of the environmental niche for all species. Changes in habitat amount and distribution reflected widespread land use changes over the past century while declines in southern and low-elevation areas are consistent with impacts from climatic change. ConclusionsOur models uncovered land use and climatic change as potential historic drivers of population change for North American weasels and provide a basis for management recommendations and targeted survey efforts. We identified potentially at-risk populations and a need for landscape-level planning to support weasel populations amid ongoing environmental changes. 

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