Paleoenvironmental Dynamics of South American Tropical Systems

The tropical systems of South America encompass expansive rainforest, grassland, montane and wetland environments that have responded dynamically to climatic oscillations, orbital forcing and human influence over millennial and orbital timescales. Palaeoenvironmental records from lake sediments, speleothems, peatlands and pollen archives reveal fluctuations in precipitation patterns governed by shifts in the Intertropical Convergence Zone, variability in the South American Monsoon System and variations in sea-surface temperature across the tropical Atlantic. During glacial–interglacial cycles, sedimentary and isotopic proxies trace changes in vegetation assemblages and moisture availability, while Holocene records document the emergence of anthropogenic fire regimes and land-use transformations. These reconstructions illustrate how orbital insolation modulates the intensity and spatial extent of convective rainfall, and how millennial-scale cold events propagate southward to alter tropical hydroclimate. Such insights are critical for contextualising the resilience and vulnerability of tropical ecosystems under present-day warming and advancing predictive models of future biodiversity and biogeochemical feedbacks.

Research from Nature Portfolio

Recent studies have extended sedimentary records in the Andean uplands, establishing the first continuous 670 000-year pollen and charcoal sequence from a high-altitude lake. This record demonstrates that grassland dominance prevailed through multiple glacial–interglacial transitions, with transient forest incursions during peak interglacials. Fire frequency remained negligible until the late Holocene, when anthropogenic burning reshaped vegetation trajectories. Parallel work harnessing high-precision speleothem δ18O chronologies in northern tropical South America has disentangled the influence of high-latitude summer insolation on Intertropical Convergence Zone migrations. These data show an antiphased rainfall response between coastal basins and inland monsoon regions, with orbital forcing exerting a stronger control on zonal displacement than local insolation. Foundational isotopic reconstructions of the South American Monsoon System spanning the Last Glacial Maximum to the mid-Holocene have provided the most detailed hydrological history yet, revealing abrupt millennial-scale dry and wet episodes linked to ice-sheet and greenhouse-gas forcing.

Paleoenvironmental Dynamics of South American Tropical Systems publication trend

The graph below shows the total number of articles in paleoenvironmental dynamics of south american tropical systems across all publications each year (not limited to Nature Index journals).

Technical terms

Intertropical Convergence Zone (ITCZ): A tropical belt of intense convective rainfall formed by the meeting of northern and southern hemisphere trade winds.

Speleothem: Mineral deposits such as stalagmites and stalactites in caves that preserve layered isotopic records of past precipitation.

South American Monsoon System (SAMS): Seasonally reversing wind and rain band over tropical South America, driven by land–sea thermal contrasts.

δ18O: The ratio of heavy to light oxygen isotopes in a sample, used as a proxy for past temperature and precipitation changes.

Pollen analysis: Examination of pollen grains in sedimentary sequences to reconstruct historical vegetation and infer climatic conditions.

Peatland: Wetland ecosystems accumulating organic matter where stratified deposits serve as high-resolution archives of environmental change.

References

1. A neotropical perspective on the uniqueness of the Holocene among interglacials. Nature Communications (2023).
2. Summer insolation controlled movements of Intertropical Convergence Zone during last glacial cycle in northern South America. Communications Earth & Environment (2023).
3. A high-resolution history of the South American Monsoon from Last Glacial Maximum to the Holocene. Scientific Reports (2017).
4. Climate variability and human impact in South America during the last 2000 years: synthesis and perspectives from pollen records. Climate of the Past (2016).
5. A high-altitude peatland record of environmental changes in the NW Argentine Andes (24∘ S) over the last 2100 years. Climate of the Past (2016).
6. Late Quaternary Variations in the South American Monsoon System as Inferred by Speleothems—New Perspectives using the SISAL Database. Quaternary (2019).