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. $\delta$¹³C-inferred vegetation changes confirm a prominent and abrupt appearance of C₄ 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. $\delta$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. Significance Modern human societies live in strongly altered ecosystems. However, anthropogenic environmental disturbances occurred long before the industrial revolution. About 2,600 y ago, a forest–savannah mosaic replaced dense rainforests in Western Central Africa. This rainforest crisis was previously attributed either to the impact of climate change or, to a lesser extent, to the expansion of Bantu peoples through Central Africa. A 10,500-y sedimentary record from Lake Barombi, Southwest Cameroon, demonstrates that the rainforest crisis was not associated with any significant hydrological change. Based on a detailed investigation of a regional archaeological database, we present evidence that humans altered the rainforest ecosystem and left detectable traces in the sediments deposited in Lake Barombi.

Early Riser: How glacial-interglacial cycles and the long-term variability of sea level depend on the amount of energy received by Earth from the Sun is unclear. Thomas et al. (p. 1186 , published online 23 April; see the cover) report results from fossil corals found in Tahiti that indicate that sea level began to rise when insolation at 65° North latitude was near a minimum, not after it had begun to rise, as predicted by the Milankovitch theory. In contrast, the timing of the last deglaciation agrees well with the Milankovitch theory. Thus, glacial cycles do not behave as simply as the Milankovitch theory suggests.

Microporous carbonates can constitute excellent hydrocarbon reservoirs if their micropore and/or nanopore structure is sufficiently developed and continuous. In such deposits, assessing the exact timing of reservoir property stabilization is critical to better understand the postdepositional processes favorable to the creation or preservation of porosity. However, placing reliable and accurate chronological constraints on the formation of microporosity in these reservoirs is a major challenge. In this study we performed absolute U-Pb dating of calcite cements occurring in the Urgonian microporous limestone (northern Tethys margin) of southeastern France. U-Pb ages ranging between 96.7 ± 4.9 Ma and 90.5 ± 1.6 Ma were obtained on the major calcitic phase responsible for the cementation, and therefore the stabilization of microporosity, indicating that this diagenetic process occurred synchronously at the regional scale following an extended subaerial exposure. Our results show that (1) the mineralogical stabilization process responsible for the formation of an excellent pervasive microporous network took place relatively early, and (2) the so-acquired reservoir quality was preserved for more than 90 m.y. These observations emphasize the importance of long exposure periods and associated meteoric influx for the formation and preservation of good microporous reservoirs.

The last deglaciation is characterized by a rapid sea-level rise and coeval abrupt environmental changes. The Barbados coral reef record suggests that this period has been punctuated by two brief intervals of accelerated melting (meltwater pulses, MWP), occurring at 14.08–13.61 ka and 11.4–11.1 ka (calendar years before present), that are superimposed on a smooth and continuous rise of sea level. Although their timing, magnitude, and even existence have been debated, those catastrophic sea-level rises are thought to have induced distinct reef drowning events. The reef response to sea-level and environmental changes during the last deglacial sea-level rise at Tahiti is reconstructed based on a chronological, sedimentological, and paleobiological study of cores drilled through the relict reef features on the modern forereef slopes during the Integrated Ocean Drilling Program Expedition 310, complemented by results on previous cores drilled through the Papeete reef. Reefs accreted continuously between 16 and 10 ka, mostly through aggradational processes, at growth rates averaging 10 mm yr⁻¹. No cessation of reef growth, even temporary, has been evidenced during this period at Tahiti. Changes in the composition of coralgal assemblages coincide with abrupt variations in reef growth rates and characterize the response of the upward-growing reef pile to nonmonotonous sea-level rise and coeval environmental changes. The sea-level jump during MWP 1A, 16 ± 2 m of magnitude in ∼350 yr, induced the retrogradation of shallow-water coral assemblages, gradual deepening, and incipient reef drowning. The Tahiti reef record does not support the occurrence of an abrupt reef drowning event coinciding with a sea-level pulse of ∼15 m, and implies an apparent rise of 40 mm yr⁻¹ during the time interval corresponding to MWP 1B at Barbados.

The North‐Western Sahara Aquifer System (NWSAS), one of the world's largest groundwater systems, shows an overall piezometric decline associated with increasing withdrawals. Estimating the recharge rate in such a semiarid system is challenging but crucial for sustainable water development. In this paper, the recharge of the NWSAS is estimated using a regional water budget based on GRACE terrestrial water storage monthly records, soil moisture from the GLDAS (a land data system that assimilates hydrological information), and groundwater pumping rates. A cumulated natural recharge rate of 1.40 ± 0.90 km³ yr⁻¹is estimated for the two main aquifers. Our results suggest a renewal rate of about 40% which partly contradicts the premise that recharge in this area should be very low or even null. Aquifer depletion inferred from our analysis is consistent with observed piezometric head decline in the two main aquifers in the region. Annual recharge variations were also estimated and vary between 0 and 4.40 km³ yr⁻¹for the period 2003–2010. These values correspond to a recharge between 0 and 6.75 mm yr⁻¹ on the 650,000 km²of outcropping areas of the aquifers, which is consistent with the expected weak and sporadic recharge in this semiarid environment. These variations are also in line with annual rainfall variation with a lag time of about 1 year.