The importance of forest islands within wet savannas for the conservation of rain forest animals.The Ivory Coast case

Trois ilôts forestiers du Parc National de la Comoé ont été étudiés au cours d'une saison sèche.Des différences entre la composition floristique et faunistique de ces forêts ont été notées.Les origines possibles de ces différences dans la structure des communautés sont discutées : les ilôts forestiers sont ils des reliques de forêts plus vastes ou bien des phases pionnières d'une recolonisation forestière? Le rôle de ces mosaïques forêt/savane dans la préservation d'espèces des forêts ombrophiles tropicales au sein de la partie la plus humide de la zone des savanes est abord

Phytolith signal of aquatic plants and soils in Chad, Central Africa

To identify the phytolith signal of lacustrine environments, which are prone to preserving faunal remains including hominins, we analyzed the phytolith content of 46 grass and sedge species, and of 26 soil and mud samples. The samples were collected in Chad (Central Africa), in the Sudanian and Sahelian phytogeographical zones, near temporary and permanent water-bodies (including Lake Chad) and in grass-dominated biomes on well-drained soils. Altogether, we observed and counted separately 80 different phytolith types, including 38 grass silica short cells (GSSCs). Phytolith type diversity and relative abundances were analyzed in the botanical specimens to improve the phytolith taxonomic resolution. For the Poaceae, we used a valuetest analysis to identify significant cohorts of phytoliths to characterize aquatic, mesophytic, and xerophytic species. Our results show that the abundance of Cyperaceae in swampy areas may be deduced from the combined abundance of blocky and elongate phytolith types, but not by the typical silicified Papillae phytoliths, which were barely found preserved in the soil/mud. The abundance of aquatic Poaceae near water-bodies is inferred from the presence and abundance of a cohort of eight GSSC types (including notably several trapeziform GSSCs within the bilobate, cross, and saddle categories), which averages 42% in the mud samples, but only 23% and 14% in the samples from the Sudanian and Sahelian zones, respectively. The characterization is unclear for mesophytic grasses, but obvious for xerophytic grasses whose abundance in the Sahelian grasslands is inferred from the presence and abundance of a cohort of five GSSC types (mainly tabular saddles), which averages 50% in the soil samples from the arid Sahelian zone, and b19% in the more humid Sudanian and swamp samples. In conclusion, considering the full morphological diversity of grass silica short cell phytoliths (rather than just the broad morphological categories) allows greater discrimination of the aquatic environments. Such approach is therefore required for analyzing vegetation distribution at a local scale. (Résumé d'auteur

Will Elephants Soon Disappear from West African Savannahs?

Precipitous declines in Africa’s native fauna and flora are recognized, but few comprehensive records of these changes have been compiled. Here, we present population trends for African elephants in the 6,213,000 km2 Sudano-Sahelian range of West and Central Africa assessed through the analysis of aerial and ground surveys conducted over the past 4 decades. These surveys are focused on the best protected areas in the region, and therefore represent the best case scenario for the northern savanna elephants. A minimum of 7,745 elephants currently inhabit the entire region, representing a minimum decline of 50% from estimates four decades ago for these protected areas. Most of the historic range is now devoid of elephants and, therefore, was not surveyed. Of the 23 surveyed elephant populations, half are estimated to number less than 200 individuals. Historically, most populations numbering less than 200 individuals in the region were extirpated within a few decades. Declines differed by region, with Central African populations experiencing much higher declines (276%) than those in West Africa (233%). As a result, elephants in West Africa now account for 86% of the total surveyed. Range wide, two refuge zones retain elephants, one in West and the other in Central Africa. These zones are separated by a large distance (,900 km) of high density human land use, suggesting connectivity between the regions is permanently cut. Within each zone, however, sporadic contacts between populations remain. Retaining such connectivity should be a high priority for conservation of elephants in this region. Specific corridors designed to reduce the isolation of the surveyed populations are proposed. The strong commitment of governments, effective law enforcement to control the illegal ivory trade and the involvement of local communities and private partners are all critical to securing the future of elephants inhabiting Africa’s northern savannas