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[1] Climate is an important control on biomass burning, but the sensitivity of fire to changes in temperature and moisture balance has not been quantified. We analyze sedimentary charcoal records to show that the changes in fire regime over the past 21,000 yrs are predictable from changes in regional climates. Analyses of paleo-fire data show that fire increases monotonically with changes in temperature and peaks at intermediate moisture levels, and that temperature is quantitatively the most important driver of changes in biomass burning over the past 21,000 yrs. Given that a similar relationship between climate drivers and fire emerges from analyses of the interannual variability in biomass burning shown by remote-sensing observations of month-by-month burnt area between 1996 and 2008, our results signal a serious cause for concern in the face of continuing global warming. , et al. (2012), Predictability of biomass burning in response to climate changes, Global Biogeochem. Cycles, 26, GB4007,

A potential human footprint on Western Central African rainforests before the Common Era has become the focus of an ongoing controversy. Between 3,000 y ago and 2,000 y ago, regional pollen sequences indicate a replacement of mature rainforests by a forest-savannah mosaic including pioneer trees. Although some studies suggested an anthropogenic influence on this forest fragmentation, current interpretations based on pollen data attribute the ''rainforest crisis'' to climate change toward a drier, more seasonal climate. A rigorous test of this hypothesis, however, requires climate proxies independent of vegetation changes. Here we resolve this controversy through a continuous 10,500-y record of both vegetation and hydrological changes from Lake Barombi in Southwest Cameroon based on changes in carbon and hydrogen isotope compositions of plant waxes. [Formula: see text]C-inferred vegetation changes confirm a prominent and abrupt appearance of C plants in the Lake Barombi catchment, at 2,600 calendar years before AD 1950 (cal y BP), followed by an equally sudden return to rainforest vegetation at 2,020 cal y BP. [Formula: see text]D values from the same plant wax compounds, however, show no simultaneous hydrological change. Based on the combination of these data with a comprehensive regional archaeological database we provide evidence that humans triggered the rainforest fragmentation 2,600 y ago. Our findings suggest that technological developments, including agricultural practices and iron metallurgy, possibly related to the large-scale Bantu expansion, significantly impacted the ecosystems before the Common Era.

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Abstract. Glacial-interglacial fluctuations in the vegetation of South Africa might elucidate the climate system at the edge of the tropics between the Indian and Atlantic Oceans. However, vegetation records covering a full glacial cycle have only been published from the eastern South Atlantic. We present a pollen record of the marine core MD96-2048 retrieved by the Marion Dufresne from the Indian Ocean ∼120 km south of the Limpopo River mouth. The sedimentation at the site is slow and continuous. The upper 6 m (spanning the past 342 Ka) have been analysed for pollen and spores at millennial resolution. The terrestrial pollen assemblages indicate that during interglacials, the vegetation of eastern South Africa and southern Mozambique largely consisted of evergreen and deciduous forests. During glacials open mountainous scrubland dominated. Montane forest with Podocarpus extended during humid periods was favoured by strong local insolation. Correlation with the sea surface temperature record of the same core indicates that the extension of mountainous scrubland primarily depends on sea surface temperatures of the Agulhas Current. Our record corroborates terrestrial evidence of the extension of open mountainous scrubland (including fynbos-like species of the high-altitude Grassland biome) for the last glacial as well as for other glacial periods of the past 300 Ka.Correspondence to: L. M. Dupont (dupont@uni-bremen.de)

Eolian dust deposited on a meteorology buoy over the boreal winter and spring of 1992/1993 in the Northeast Atlantic off Northwest Africa (18°N, 22°W) afforded sufficient material for detailed assessment of its biogeochemical characteristics and provenance. The sample was subjected to microscopic examination and bulk, elemental, isotopic, black carbon, and molecular (lignin, lipid) analyses. The bulk elemental composition and organic carbon (OC) content (1.02% dry weight) establishes the dust's origin as continental upper crust and is typical of dusts that emanate from West Africa. These data are in accord with the extensive satellite imagery documenting the transit of dust clouds from the Sahara and Sahel regions (e.g., NASA TOMS aerosol index). Microscopic examination reveals that charcoal‐like particles from vegetation fires (“black carbon” (BC)) are the most abundant morphologically distinct organic components. Accelerator mass spectrometry (AMS) 14C analysis yields conventional 14C ages for bulk OC of 1260 ± 40 years and BC of 2070 ± 35 years. Taken together with corresponding stable carbon isotopic compositions (δ13C, −18.9 and −15.1‰, respectively), these results suggest the presence of biomass and burning residues derived from predominantly C4 vegetation that accumulated in soils over the late Holocene. Molecular‐level measurements are also consistent with this scenario. For example, lignin‐derived phenols in the dustfall sample indicate a significant contribution of angiosperm grass‐type tissue. The altered nature of the lignin suggests storage as residues in soils. Solvent extractable (lipid) constituents include a marked leaf wax type component with a molecular and stable carbon isotopic composition similar to those observed in surface marine sediments in this region. The hydrocarbon fraction contained some diesel‐type contamination but the n‐alkanes (C23–C33) retained a prominent odd/even distribution, with δ13C ranging from −26.7 to −28.5‰. The suite of even carbon numbered n‐alkanols (C22–C32) is 14C dated at 647 ± 150 years, with δ13C values ranging from −23.9 to −30.4‰. The long‐chain n‐alkanoic acids (C22–C32) exhibited δ13C values ranging from −22.6 to −27.4‰. These waxes are evidently a mixed signal derived from contemporary C3 and C4 vegetation and from ablated soils and desiccated lake sediments of middle to late Holocene age. This molecular approach shows promise as a tool for continental paleoenvironmental assessment, particularly with respect to past vegetation cover, regional aridity, and wind systems.

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