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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. 

The African Pollen Database is a scientific network with the objective of providing the international scientific community with data and tools to develop palaeoenvironmental studies in sub-Saharan Africa and to provide the basis for understanding the vulnerability of ecosystems to climate change. This network was developed between 1996 and 2007. It promoted the collection, homogenization and validation of pollen data from modern (trap, soils, lake and river mud) and fossil materials (Quaternary sites) and developed a tool to determine pollen grains using digital photographs from international herbaria. Discontinued in 2007 due to a lack of funding, this network now resumes its activity in close collaboration with international databases: Neotoma, USA, Pangaea, DE, and the Institut Pierre Simon Laplace, FR. 

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. 

Global vegetation over the past 18,000 years has been transformed first by the climate changes that accompanied the last deglaciation and again by increasing human pressures; however, the magnitude and patterns of rates of vegetation change are poorly understood globally. Using a compilation of 1181 fossil pollen sequences and newly developed statistical methods, we detect a worldwide acceleration in the rates of vegetation compositional change beginning between 4.6 and 2.9 thousand years ago that is globally unprecedented over the past 18,000 years in both magnitude and extent. Late Holocene rates of change equal or exceed the deglacial rates for all continents, which suggests that the scale of human effects on terrestrial ecosystems exceeds even the climate-driven transformations of the last deglaciation. The acceleration of biodiversity change demonstrated in ecological datasets from the past century began millennia ago. 

Modern Homo sapiens engage in substantial ecosystem modification, but it is difficult to detect the origins or early consequences of these behaviors. Archaeological, geochronological, geomorphological, and paleoenvironmental data from northern Malawi document a changing relationship between forager presence, ecosystem organization, and alluvial fan formation in the Late Pleistocene. Dense concentrations of Middle Stone Age artifacts and alluvial fan systems formed after ca. 92 thousand years ago, within a paleoecological context with no analog in the preceding half-million-year record. Archaeological data and principal coordinates analysis indicate that early anthropogenic fire relaxed seasonal constraints on ignitions, influencing vegetation composition and erosion. This operated in tandem with climate-driven changes in precipitation to culminate in an ecological transition to an early, pre-agricultural anthropogenic landscape. 

African ecosystems hold enormous ecological and economic value due to high biodiversity (Myers et al. 2000) and valuable ecosystem services provided to urban and agrarian populations (Wangai et al. 2016). However, these services are vulnerable to land use and climate change (Niang et al. 2014). Long paleoecological records from Africa provide iconic examples of abrupt environmental change, offering critical evidence for tipping points in the Earth system. Datasets in the region are notoriously difficult to access with the African Pollen Database (APD) largely unsupported for the last decade. Poor data accessibility has been a community complaint.