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Kilimanjaro is experiencing the consequences of climate change and multiple land-use pressures. Few paleoenvironmental and archeological records exist to examine historical patterns of late Holocene ecosystem changes on Kilimanjaro. Here we present pollen, phytolith, and charcoal (>125 μm) data from a palustrine sediment core that provide a 3000-year radiocarbon-dated record collected from a wetland near the headwaters of the Maua watershed in the alpine and ericaceous vegetation zones. From 3000 to 800 cal yr BP, the pollen, phytolith, and charcoal records show subtle variability in ericaceous and montane forest assemblages with apparent multicentennial secular variability and a long-term pattern of increasing Poaceae and charcoal. From 800 to 600 cal yr BP, montane forest taxa varied rapidly, Cyperaceae abundances increased, and charcoal remained distinctly low. From 600 yr cal BP to the present, woody taxa decreased, and ericaceous taxa and Poaceae dominated, with a conspicuously increased charcoal influx. Uphill wetland ecosystems are crucial for ecological and socioeconomic resilience on and surrounding the mountain. The results were synthesized with the existing paleoenvironmental and archaeological data to explore the high spatiotemporal complexity of Kilimanjaro and to understand historical human-environment interactions. These paleoenvironmental records create a long-term context for current climate, biodiversity, and land-use changes on and around Kilimanjaro.

In Africa there is a scarcity of information on how plant species that can provide forage for honey bees vary across differentially structured landscapes, and what are the implications of such variabilities on colony integrity. This research presents new insights into the diversity and richness of pollen collected by Apis mellifera scutellata, a subspecies of the Western honey bee native to sub-Saharan Africa, at six study sites of different degradation levels within a semi-arid landscape in Kenya. Ten colonies were established at each site and land cover characteristics were extracted using novel remote sensing methods. The sites differed by the proportions of natural vegetation, cropland, grassland and hedges within each site. Bee bread was collected five times, with three colonies in each of the six sites repeatedly sampled during the period from May 2017 to November 2018. Pollen identification and protein analysis within the study sites were thereafter conducted to establish the linkage between landscape degradation levels and abundance and diversity of pollen. Out of 124 plant species identified, Terminalia spp., Cleome spp. and Acacia spp. were identified as the most abundant species. Moreover, species richness and diversity were highest in the two sites located in moderately degraded landscapes. Pollen protein content showed statistically significant differences across season rather than geographical location. This study demonstrated that landscape degradation negatively affected the diversity and richness of pollen collected by honey bees. Consequently, this helps our understanding of native honey bees’ forage resource usage and plant species preferences in landscapes with varying degrees of degradation.

The Middle Stone Age in Africa The Olorgesailie basin in the southern Kenya rift valley contains sediments dating back to 1.2 million years ago, preserving a long archaeological record of human activity and environmental conditions. Three papers present the oldest East African evidence of the Middle Stone Age (MSA) and elucidate the system of technology and behavior associated with the origin of Homo sapiens . Potts et al. present evidence for the demise of Acheulean technology that preceded the MSA and describe variations in late Acheulean hominin behavior that anticipate MSA characteristics. The transition to the MSA was accompanied by turnover of large mammals and large-scale landscape change. Brooks et al. establish that ∼320,000 to 305,000 years ago, the populations in eastern Africa underwent a technological shift upon procurement of distantly sourced obsidian for toolmaking, indicating the early development of social exchange. Deino et al. provide the chronological underpinning for these discoveries. Science , this issue p. 86 , p. 90 , p. 95

Characterizing eastern African environmental variability on orbital timescales is crucial to evaluating the hominin evolutionary response to past climate changes. However, there is a dearth of high-resolution, well-dated records of ecosystem dynamics from eastern Africa that cover long time intervals. In the last 1 Myr, there were significant anatomical and cultural developments in Homo, including the origin of Homo sapiens. There were also major changes in global climatic boundary conditions that may have affected eastern African environments, yet potential linkages remain poorly understood. We developed carbon isotopic records from plant waxes (δ13Cwax) and bulk organic matter (δ13COM) from a well-dated sediment core spanning the last ∼1 Myr extracted from the Koora Basin, located south of the Olorgesailie Basin, in the southern Kenya rift. Our record characterizes the climatic and environmental context for evolutionary events and technological advances recorded in the adjacent Olorgesailie Basin, such as the transition from Acheulean to Middle Stone Age tools by 320 ka. A significant shift toward more C4-dominated ecosystems and arid conditions occurred near the end of the mid-Pleistocene Transition, which indicates a link between equatorial eastern African and high-latitude northern hemisphere climate. Environmental variability increases throughout the mid- to late-Pleistocene, superimposed by precession-paced packets of variability modulated by eccentricity. An interval of particularly high-amplitude climate and environmental variability occurred from ∼275 ka to ∼180 ka, synchronous with evidence for the first H. sapiens fossils in eastern Africa. These results support the ‘variability selection hypothesis’ that increased environmental variability selected for adaptable traits, behaviors, and technology in our hominin ancestors.

East African landscapes today are the result of the cumulative effects of climate and land-use change over millennial timescales. In this review, we compile archaeological and palaeoenvironmental data from East Africa to document land-cover change, and environmental, subsistence and land-use transitions, over the past 6000?years. Throughout East Africa there have been a series of relatively rapid and high-magnitude environmental shifts characterised by changing hydrological budgets during the mid- to late Holocene. For example, pronounced environmental shifts that manifested as a marked change in the rainfall amount or seasonality and subsequent hydrological budget throughout East Africa occurred around 4000, 800 and 300 radiocarbon years before present (yr BP). The past 6000?years have also seen numerous shifts in human interactions with East African ecologies. From the mid-Holocene, land use has both diversified and increased exponentially, this has been associated with the arrival of new subsistence systems, crops, migrants and technologies, all giving rise to a sequence of significant phases of land-cover change. The first large-scale human influences began to occur around 4000?yr BP, associated with the introduction of domesticated livestock and the expansion of pastoral communities. The first widespread and intensive forest clearances were associated with the arrival of iron-using early farming communities around 2500?yr BP, particularly in productive and easily-cleared mid-altitudinal areas. Extensive and pervasive land-cover change has been associated with population growth, immigration and movement of people. The expansion of trading routes between the interior and the coast, starting around 1300?years ago and intensifying in the eighteenth and nineteenth centuries CE, was one such process. These caravan routes possibly acted as conduits for spreading New World crops such as maize (Zea mays), tobacco (Nicotiana spp.) and tomatoes (Solanum lycopersicum), although the processes and timings of their introductions remains poorly documented. The introduction of southeast Asian domesticates, especially banana (Musa spp.), rice (Oryza spp.), taro (Colocasia esculenta), and chicken (Gallus gallus), via transoceanic biological transfers around and across the Indian Ocean, from at least around 1300?yr BP, and potentially significantly earlier, also had profound social and ecological consequences across parts of the region.\ud \ud Through an interdisciplinary synthesis of information and metadatasets, we explore the different drivers and directions of changes in land-cover, and the associated environmental histories and interactions with various cultures, technologies, and subsistence strategies through time and across space in East Africa. This review suggests topics for targeted future research that focus on areas and/or time periods where our understanding of the interactions between people, the environment and land-cover change are most contentious and/or poorly resolved. The review also offers a perspective on how knowledge of regional land-use change can be used to inform and provide perspectives on contemporary issues such as climate and ecosystem change models, conservation strategies, and the achievement of nature-based solutions for development purposes.

The most common grass phytoliths from “Zambezian” miombos are described here for the first time. Their potential for long term preservation in sediments makes them a useful tool in the reconstruction of ancient plant communities and plant/human interactions. We processed 60 plant samples (26 identified genera and species), with an average of 300 phytoliths counted per sample to a total of 18,586. Forty-seven morphotypes were described as per the International Code for Phytolith Nomenclature, with exceptions, including forty-five discreet shapes and two articulated forms, which can be used as comparative reference materials. We conducted three forms of statistical analyses: Discriminant Analysis, Cluster Analysis, and Principal Component Analysis. The highest biomineral content was recorded among the Bambuseae and Paniceae, while the lowest silica production is detected in the Cynodonteae tribe. Typologically, the subfamily Panicoideae yielded 50% of the types reported here, 32% are from the Chloridoideae, 12% from the Bambusoideae, and 8% from the Arundinoideae sensu lato. Overall, the idealized Zambezian Poaceae phytolith spectrum is dominated by a small subset of Poaceae short cells, which include five morphotypes conventionally associated with Panicoid grasses (Bilobate concave outer margin long shaft, Bilobate concave outer margin short shaft, Bilobate convex outer margin long shaft, Bilobate convex outer margin short shaft, Cross), one morphotype commonly seen in Chloridoid taxa (saddle), and two types that appear across subfamily boundaries (tower, tower horned). The next logical step to take in regional phytolith research is the account of phytoliths deposited in soils underneath living plants, for they represent the interface between existing vegetation communities and the inevitably distorted fossil assemblages that the paleobotanist uses for environmental reconstruction.

Pollen and charcoal data generated from a 1469 cm core, radiocarbon dated to 26,430 14 C yr BP, recovered from Rumuiku Swamp on the southeast of Mount Kenya, are used to document changes in the distribution and composition of montane vegetation and fire regimes over the Late Quaternary. Throughout the transition from the Last Glacial Maximum (LGM), high resolution (sub-centennial scale) analysis documents a highly dynamic ecosystem and fire regime. The pollen record shows that under a cool, but rather moist LGM climate, Ericaceae and Stoebe species shifted down-slope more than 1000 m relative to the present day. Rather than simple altitudinal lowering of current vegetation zonation, these taxa formed a vegetation assemblage that mixed high altitude components with relatively lowland taxa; in particular Juniperus that is presently found at altitudes lower than the study site, but on the drier side of Mount Kenya. There is noticeable addition and co-dominance of Hagenia to the ecosystem from 20,500 14 C yr BP, until around 14,000 14 C yr BP when a mix of Ericaceous Belt and upper montane forest taxa, such as Artemisia , Polycias , Schefflera and Stoebe , dominated the initial development of montane forest. Reduced levels of Hagenia , Juniperus , Olea and Podocarpus are recorded about the time of the Younger Dryas with highly variable presence of more mesic taxa such as Polyscias and Schefflera . This development of montane forest over the Late Pleistocene to Holocene transition reflects a significant reorganization of the ecosystem composition that was heavily influenced by a variable fire regime. Shifts in vegetation composition reflect the onset of a warmer moist climate from the beginning of Holocene, as mixed montane forest became more established. The latter part of the Holocene registers human impact and forest clearance with increased anthropogenic impact marked by a transition to open vegetation and increased fire frequency.

East African ecosystems are shaped by long-term interaction with changing climate, human population, fire and wildlife. There remains today a strong connection between people and ecosystems, a relationship that is being strained by the rapidly developing and growing East African population, and their associated resource needs. Predicted climatic and atmospheric change will further impact on ecosystems culminating in a host of challenges for their management and sustainable development, further compounded by a backdrop of political, land tenure and economic constraints. Given the many direct and indirect benefits that ecosystems provide to surrounding human populations, understanding how they have changed over time and space deserves a special place on the ecosystem management agenda. Such a perspective can only be derived from a palaeoecology, particularly where there is high resolution, both through time and across space. The East African palaeoecological archive is reviewed, in particular to assess how it can meet this need. Although there remain crucial gaps, the number of palaeoecological archives from East Africa growing rapidly, some employing new and novel techniques to trace past ecosystem response to climate change. When compared to the archaeological record it is possible to disentangle human from climate change impacts, and how the former interacts with major environmental changes such as increased use of fire, changing herbivore densities and increased atmospheric CO2 concentration. With this multi-dimensional perspective of environmental change impacts it is imperative that our understanding of past human-ecosystem interactions are considered to impart effective long term management strategies; such an approach will enhance possibilities for a sustainable future for East African ecosystems and maximise the livelihoods of the populations that rely on them.