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The end of the Holocene Humid Period was characterized by the massive collapse of forest ecosystems in central Africa. Was this large-scale environmental crisis dated between 3300 and 2500 years BP at the origin of the present-day wooded-grassland/forest mosaic of central Cameroon? Here we present carbon isotope data on soil organic matter collected from 29 sites from this area, including the Grassfield plateaus, with the aim of characterizing this environmental crisis and discussing the origin of the present-day landscape. 14C data on total soil organic matter and charcoal fragments show that the organic matter in these soils originates from the Holocene. In our forest sites, the δ13C profiles do not show any marked alteration of the forest cover throughout the Holocene. Discrete traces of forest expansion or retreat are observed only punctually at the forest margins. In the wooded-grassland/forest mosaic zone, the environmental crisis was of reduced amplitude. In the present grassland and wooded grassland areas, there was no true forest during the lower to middle Holocene, but a markedly more tree-covered landscape. The timing of this crisis revealed by our 14C measurements, although only indicative at this stage, suggests that it occurred earlier at higher altitudes than in the lowlands due to marked topographic relief favoring drainage along the slopes. These results fit a climatic rather than anthropogenic origin of the vegetation opening in this region. [ABSTRACT FROM AUTHOR]

Using Cameroonian data, this paper investigates the effects of social network on wage. Social network is measured in terms of using friends and relatives while looking for a job. In order to evaluate the effectiveness of social network with regard to wage, we make use of Heckman selection model. Our findings contrast with previous studies. After factoring the endogeneity and sample selection, we find that Job seekers who make use of social network exhibit a wage premium of 1.53 per cent of average wage. We also find that social network contributes to explain wage differential according to gender and institutional sectors (formal versus informal). [ABSTRACT FROM AUTHOR]

A study of the pollen content and organic matter of a 6 m long core recovered from the gallery forest alongside the tributary of Lake Petpenoun, not far from its mouth (NW Cameroon, 5°38′29.3 N, 10°38′43.1E, 1120 m asl) documents the evolution of the « Grassfields region » over the last millennium. The exceptional rate of accumulation of the sedimentary series, where the last millennium is 5 m thick, allows to differentiate two distinct periods. Between 900 and 1420 CE, the coring site was located under lake water, reflecting the expansion of the lake under humid environmental conditions during the Medieval Climate Anomaly (MCA). The coring site then gradually dried up from 1420 CE onward, during the Little Ice Age (LIA). Then, in 1850 CE, modern conditions were established. During the LIA, the lake edge moved about 140 m downstream of the coring site due to drying conditions. The date of 1420 CE corresponds to a major event that affected not only local hydrological conditions but also regional vegetation. The collapse of pollen production shows the general degradation of the landscape due to increased drought conditions. • Environmental changes at Lake Petpenoun (Cameroon) during the last millennium • Humid conditions characterize the MCA and the MCA/LIA transition up to 1420 CE • A major evironmental change occurred around 1420 CE • A gradual drying trend set in during the LIA and ended by 1850 CE. • The modern climate and environment were established by 1850 CE. [ABSTRACT FROM AUTHOR]

Abstract: In order to better understand the dynamics of the forest–savanna mosaic from central Cameroon, we analyzed 13C and 14C profiles of six oxisols: two under forests and four under savannas. The δ 13C soil profiles collected in the forests indicate that these environments are stable at least since the mid-Holocene, whereas the areas currently covered by savannas were formerly occupied by more forested vegetations. The 14C dating of organic matter indicate that the late extension of the savannas in central Cameroon date from the Late Holocene, starting from 4000–3500 14C yr BP. [Copyright &y& Elsevier]