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Building resilience to climate change in the Afrotropics hinges on accurately predicting the style and tempo of ecosystem responses. Paleoecological records offer valuable insights into vegetation dynamics, yet high-resolution data sets remain scarce in Africa. Here, we present a new radiocarbon-dated sediment core from Lake Tanganyika, capturing terrestrial ecosystem responses to hydroclimate variability and fire activity during the Common Era. Phytolith and macrocharcoal records reveal oscillations between grasslands and woodlands in the Zambezian miombo region, transitioning from “stable” to “unstable” states depending on fire disturbance levels. The expansion of grasslands was facilitated by reduced precipitation, increased fire activity, and ecosystem interactions. Our data sets provide new constraints regarding the timing and landscape responses within the Lake Tanganyika watershed to global hydroclimate changes, including the relatively dry Medieval climate anomaly (ca. 1000−1250 CE) and the two phases of the Little Ice Age. Cold and wet conditions, which favored tree encroachment, prevailed during the “early” Little Ice Age (ca. 1250−1530 CE), whereas drier conditions coupled with increased fire activity during the “main” Little Ice Age (ca. 1530−1850 CE) promoted the expansion of open grasslands. Significant changes in grassland-woodland communities were driven and modulated by hydroclimate and rapid ecosystem feedbacks. Fire activity served as both a disruptive force, facilitating the opening of landscapes and restricting the encroachment of trees, and a steadying control that promoted a grassland “stable state” in the tropical savannas surrounding Lake Tanganyika. Understanding shifting vegetation patterns throughout the Common Era offers valuable insights for developing biodiversity conservation strategies, sustainable land-use practices, and the maintenance of ecosystem services provided by miombo woodlands for millions of rural poor in the Lake Tanganyika basin. 

Tropical mountain ecosystems hold immense ecological and economic importance, yet they face disproportionate risks from shifting tropical climates. For example, present-day montane vegetation of East Africa is characterized by different plant species that grow in and are restricted to certain elevations due to environmental tolerances. As climate changes and temperature/rainfall zones move on mountains, these species must rapidly adjust their ranges or risk extinction. Paleoenvironmental records offer valuable insights into past climate and ecosystem dynamics, aiding predictions for ongoing climate change impacts. In particular, warming and wetting in tropical East Africa during the mid-Holocene resulted in both lowland and highland forest expansion. However, the relative impacts of rainfall and temperature change on montane ecosystems along with the influence of lowland forest expansion on montane communities is not completely understood. We use fossil pollen to study the vegetation changes in two lakes at different altitudes in the Rwenzori Mountains, Uganda: Lake Mahoma (Montane Forest belt) and Upper Kachope Lake (Afroalpine belt). Further, using the newly relaunched African Pollen Database and recent temperature reconstructions, we provide a regional synthesis of vegetation changes in the Rwenzori and then compare this with changes observed from other equatorial East African montane sites (particularly Mt Kenya). In the early to mid-Holocene in the Rwenzori Mountains, trees common today in lowland forests dominated, driven largely by warmer temperatures. After 4000 years ago (4ka), Afromontane forest trees along with grasses progressively replaced lowland trees. Not all sites experienced identical transitions. For instance, at Lake Rutundu on Mt Kenya at the same elevation as Lake Mahoma, bamboo expansion preceded Afromontane forest growth, likely influenced by variations in fire. Variance partitioning indicates that each site responded differently to changes in temperature and rainfall. Therefore, these site-specific ecological responses underscore the importance of considering biogeographic legacies as management strategies are developed, despite similarities in modern ecology. 

Landscapes are formed by long-term interactions between the underlying geology and climatic, edaphic and biotic factors, including human activity. The Kasitu Valley in the Mzimba District of northern Malawi includes the Kasitu River and its adjacent floodplains and uplands, and it has been a location of sustained human occupation since at least 16 thousand years ago (ka) based on archaeological excavations from rockshelters. We trace the changing ecology and geomorphology of the region through soil stable isotopes (δ¹³C, δ¹⁵N), microcharcoal and fossil pollen analysed from alluvial terraces dated by Optically Stimulated Luminescence, and wetland auger cores and archaeological sites dated by radiocarbon. Our results suggest that the region was primarily covered in mosaic forest at ca. 22.5 ka. Middle and Late Holocene samples (6.0–0.5 ka) show an increasingly open, herbaceous landscape over time with an inflection toward more abundant C4 vegetation after 2 ka. Significant upland erosion and terrace formation is also evidenced since 2 ka alongside high concentrations of microcharcoal, suggesting more intensive use of fire. Faecal biomarkers simultaneously indicate higher numbers of humans living adjacent to the archaeological site of Hora 1, which may be indicative of an overall population increase associated with the arrival of Iron Age agropastoralists. More recently, the introduction of exogenous commercial taxa such asPinussp. are correlated with regional afforestation in our proxy record. These results show increasing stepwise human impacts on the local environment, with deforestation and maintenance of open landscapes correlated with the regional introduction and intensification of agriculture during the Late Holocene. 

Abstract We examine major reorganizations of the terrestrial ecosystem around Mono Lake, California during the last deglacial period from 16,000–9,000 cal yr BP using pollen, microcharcoal, and coprophilous fungal spores (Sporormiella) from a deep-water sediment core. The pollen results record the assemblage, decline, and replacement of a mixed wooded community of Sierran and Great Basin taxa with Alkali Sink and Sagebrush Steppe biomes around Mono Lake. In particular, the enigmatic presence ofSequoiadendron-type pollen and its extirpation during the early Holocene hint at substantial biogeographic reorganizations on the Sierran-Great Basin ecotone during deglaciation. Rapid regional hydroclimate changes produced structural alterations in pine–juniper woodlands facilitated by increases in wildfires at 14,800 cal yr BP, 13,900 cal yr BP, and 12,800 cal yr BP. The rapid canopy changes altered the availability of herbaceous understory plants, likely putting pressure on megafauna populations, which declined in a stepwise fashion at 15,000 cal yr BP and 12,700 cal yr BP before final extirpation from Mono Basin at 11,500 cal yr BP. However, wooded vegetation communities overall remained resistant to abrupt hydroclimate changes during the late Pleistocene; instead, they gradually declined and were replaced by Alkali Sink communities in the lowlands as temperature increased into the Early Holocene, and Mono Lake regressed. 

The Late-Holocene history of hydroclimatic variability in the Atacama Desert offers insights into the effects of precipitation and humans on ecosystems in one of the most extremely arid regions of the world. However, understanding the effects of regional precipitation variability in relation to local ecological stressors remains to be fully resolved. Here, we present a pollen-based qualitative precipitation reconstruction derived from fossil rodent middens recovered from two sites near Laguna Roja (LRO; n = 25) and Isluga (ISL; n = 15) in the Atacama highlands (19°S) of northern Chile. At LRO, the fossil pollen record shows multi-centennial hydroclimatic anomalies during the last millennium, with wetter than present phases at 1155–1130, 865–670, and 215–80 cal yrs BP, and similar to present conditions between 1005 and 880 cal yrs BP. In contrast, the ISL record shows a wet phase during 1115–840 cal yrs BP, suggesting that meso-ecological processes were as important in vegetation turnover as regional hydroclimate anomalies. Wetter conditions derived from LRO partially overlap with the Medieval Climate Anomaly (865–670 cal yrs BP) and with the latest part of the Little Ice Age (215–80 cal yrs BP). Furthermore, no strong anthropogenic signal was identified possibly related to the remote location of the records. Palynological diversity analyses evidence increasing diversification of plant communities during wet events at both sites. In correlation to existing regional hydroclimatic records from the Western Andes, our precipitation reconstruction verifies that centennial-scale changes in the strength of the South American Summer Monsoon (SASM) and partial influence of El Niño-like (ENSO) conditions drove vegetation turnover in the Atacama Desert during the last millennium. 

Abstract People could have hunted Madagascar’s megafauna to extinction, particularly when introduced taxa and drought exacerbated the effects of predation. However, such explanations are difficult to test due to the scarcity of individual sites with unambiguous traces of humans, introduced taxa, and endemic megaherbivores. We excavated three coastal ponds in arid SW Madagascar and present a unique combination of traces of human activity (modified pygmy hippo bone, processed estuarine shell and fish bone, and charcoal), along with bones of extinct megafauna (giant tortoises, pygmy hippos, and elephant birds), extirpated fauna (e.g., crocodiles), and introduced vertebrates (e.g., zebu cattle). The disappearance of megafauna from the study sites at ~ 1000 years ago followed a relatively arid interval and closely coincides with increasingly frequent traces of human foraging, fire, and pastoralism. Our analyses fail to document drought-associated extirpation or multiple millennia of megafauna hunting and suggest that a late combination of hunting, forest clearance, and pastoralism drove extirpations. 

The Arabian Peninsula hosts some of the most extreme environments in the world. Arabian ecosystems are largely semi-arid to hyper-arid and yet are often highly biodiverse and unique owing to a location at a biogeographic nexus. There is an urgent need to better understand ecosystem resilience to biotic and abiotic disturbance; however, the modern vegetation across much of the sub-continent is still poorly understood. Palaeoecological records in Arabia have the potential to fill in gaps in our fundamental understanding of vegetation responses to climate, disturbance, and human modification; however, to do this, data must be accessible and easy to find. To this end, within the framework of the relaunch of the African Pollen Database, here we review existing palaeoecological datasets from the Arabian Peninsula, inventory those which are available, and synthesize results from these records. Due to the dearth of pre-Holocene information, this synthesis focuses on reconstructing vegetation from the Holocene Humid Period to today with emphasis on the impact of aridification and changing human livelihoods and culture on landscapes. Finally, as Arabia is perhaps the least well-studied region within the African Pollen Database, we offer some suggestions about fruitful directions for future palaeoecological research in this area.