Andean uplift played a fundamental role in shaping South American climate and species distribution, but the relationship between the rise of the Andes, plant composition, and local climatic evolution is poorly known. We investigated the fossil record (pollen, leaves, and wood) from the Neogene of the Central Andean Plateau and documented the earliest evidence of a puna-like ecosystem in the Pliocene and a montane ecosystem without modern analogs in the Miocene. In contrast to regional climate model simulations, our climate inferences based on fossil data suggest wetter than modern precipitation conditions during the Pliocene, when the area was near modern elevations, and even wetter conditions during the Miocene, when the cordillera was around ~1700 meters above sea level. Our empirical data highlight the importance of the plant fossil record in studying past, present, and future climates and underscore the dynamic nature of high elevation ecosystems.

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Aim: Multiple abiotic and biotic factors, mainly the amount and seasonality of precipitation, fire regime, soil properties and species adaptation strategies, have been invoked to explain the existence of the tropical savanna-humid forest transition. We explored the rainfall variables that influence the probability of forest or savanna occurring in northwest South America, specifically monthly precipitation and the mean and maximum duration of wet and dry spells, defined as the number of consecutive wet (dry) days.

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We analyzed sediment cores from coastal Lake Izabal, Guatemala, to infer Holocene biogeochemical changes in the lake. At ca. 8370 calibrated yr B.P. (cal. yr B.P.), marine waters entered the lake, which presently lies ~38 km from the Caribbean coast. Temporal correlation between Early Holocene drainage of high-latitude Lakes Agassiz and Ojibway (in North America) and marine flooding of Lake Izabal suggests a causal link between the two processes. Our data indicate a relative sea-level jump of 2.60 ± 0.88 m, which is larger than previous estimates of sea-level rise during the 8.2 ka event. The inferred sea-level jump, however, cannot be explained solely by the volume of water released during drainage of Lakes Agassiz and Ojibway. Instead, we propose that previous studies underestimated the magnitude of Lakes Agassiz and Ojibway discharge, or that additional meltwater sources contributed to global sea-level rise at that time.

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Rapid degradation of freshwater ecosystems threatens water supply for human populations and natural landscapes. At diverse time scales, this process has been clearly associated with climatic and anthropogenic forcings. The question remains, however, how tropical lakes have responded to these two sources of variability. We present a multiproxy record from Lake San Lorenzo, Lagunas de Montebello National Park, tropical Mexico, spanning the last ~3400 years. We used multi‐elemental concentrations, and Cladocera and pollen assemblages along the record to reconstruct regional and local environmental variability, aiming to infer the factors and processes involved in the evolution of the lacustrine system. A principal component analysis on the pooled biological and geochemical evidence allowed the inference of the main changes in lake level and productivity. At millennial scales, the development of the lake system has been closely associated with regional moisture availability, with wetter (drier) time intervals associated with high (low) lake stands. According to Ti concentrations, from ~3400 to 1000 cal. a BP, regional conditions followed a trend towards drier conditions, with littoral cladoceran assemblages suggesting high lake productivity. The extreme regional droughts reportedly associated with the cultural collapse of the Maya civilization manifested in our study area through both high lake productivity and the lowest lake levels of the record. Through the last ~800 years, the regional moisture availability has increased, with the water body becoming deeper and larger. Overall, our record offers evidence of a highly variable system strongly coupled with regional climates, but also very sensitive to local disturbances associated with human occupation. Lake San Lorenzo has been highly resilient to external pressures and has previously recovered from conditions probably alike those associated with the ongoing modern deterioration process. Nevertheless, such recovery involves a complex network of interactions amongst natural and human factors.