Legacy of logging roads in the Congo Basin: how persistent are the scars in forest cover?

Logging roads in the Congo Basin are often associated with forest degradation through fragmentation and access for other land uses. However, in concessions managed for timber production, secondary roads are usually closed after exploitation and are expected to disappear subsequently. Little is known about the effectiveness of this prescription and the factors affecting vegetation recovery rate on abandoned logging roads. In a novel approach we assessed logging roads as temporary elements in the forest landscape that vary in persistence depending on environmental conditions. We analyzed road persistence during the period 1986–2013 in adjacent parts of Cameroon, Central African Republic and Republic of Congo. Three successive phases of road recovery were identified on LANDSAT images: open roads with bare soil, roads in the process of revegetation after abandonment and disappeared roads no longer distinguishable from the surrounding forest. Field based inventories confirmed significant differences between all three categories in density and richness of woody species and cover of dominant herbs. We used dead-end road segments, built for timber exploitation, as sampling units. Only 6% of them were identified as being re-opened. Survival analyses showed median persistence of four years for open roads before changing to the revegetating state and 20 years for revegetating roads before disappearance. Persistence of revegetating roads was 25% longer on geologically poor substrates which might result from slower forest recovery in areas with lower levels of soil nutrient content. We highlight the contrast amongst forests growing on different types of substrate in their potential for ecosystem recovery over time after roads have been abandoned. Forest management plans need to take these constraints into account. Logging activities should be concentrated on the existing road network and sites of low soil resource levels should be spared from business-as-usual exploitation. (Résumé d'auteur

Motives for khat use and abstinence in Yemen - a gender perspective

<p>Abstract</p> <p>Background</p> <p>Khat consumption is widespread in Yemeni society and causes problems both in economic development and public health. Preventive measures have been largely unsuccessful and the cultivation continues to proliferate. The gender-specific motives for khat use and abstinence were studied to create a toe-hold for more specific interventions.</p> <p>Methods</p> <p>In a quota sample with equal numbers of males, females, abstainers and consumers, 320 subjects were interviewed on their specific opinions about khat and its impact on subjective and public health, and on social and community functioning. Strata were compared in their acceptance and denial of opinions. Notions that could predict abstinence status or gender were identified with multivariate logistic regression analysis.</p> <p>Results</p> <p>Male khat users had a strong identification with khat use, while females were more ambivalent. The notion that khat consumption is a bad habit (odds ratio (OR) 3.4; p < 0.001) and consumers are malnuorished (OR 2.2; p = 0.046) were associated with female gender among khat users. Among the females worries about health impact (OR 3.2; p = 0.040) and loss of esteem in the family (OR 3.1; p = 0.048) when using khat predicted abstinence. Male abstainers opposed khat users in the belief that khat is the cause of social problems (OR 5.1, p < 0.001). Logistic regression reached an accuracy of 75 and 73% for the prediction of abstinence and 71% for gender among consumers. (All models p < 0.001.)</p> <p>Conclusions</p> <p>Distinct beliefs allow a differentiation between males, females, khat users and abstainers when targeting preventive measures. In accordance to their specific values female khat users are most ambivalent towards their habit. Positive opinions scored lower than expected in the consumers. This finding creates a strong toe-hold for gender-specific public health interventions.</p

Characterization of the aquifers of the Bangui urban area, Central African Republic, as an alternative drinking water supply resource

This paper presents the results of a survey carried out in 2010 aimed at evaluating the type and quality of the groundwater resources of the Bangui region of the Central African Republic. This work is the first step towards the development of groundwater resources in the Central African Republic in order to find alternatives to direct pumping from the Ubangi River and provide the population of the suburbs with a safer drinking water supply from deep boreholes. By combining both geological and hydrogeochemical approaches, it appears that the geology of Bangui is favourable to the development of a secure and sustainable water supply from groundwater provided that the conditions of exploitation would be constrained by the local authorities. The deep Precambrian carbonate aquifers, known as the Bimbo and Fatima formations, are identified as target resources in view of the relatively good quality of their water from the chemical point of view, and the semi-confined structure of the aquifers that prevents the mixing with shallow aquifers that are already strongly affected by domestic and industrial pollution. The main difficulty in terms of exploitation is to appreciate the depth of the resource and the more or less fractured/palaeo-karstified type of the porosity

Caractérisation de la baisse hydrologique actuelle de la rivière Oubangui à Bangui, République Centrafricaine

National audienceThe Ubangui River in Bangui comes from The Mbomu River, the CAR side and the Uele River from the DRC. Its flow till Bangui in the bottom has 546 kilometers long and has numerous anastomoses, sprinkled with a good deal of islands and strangulations (Palambo and Bangui). Its side basin is influenced by the Sudano-Guinean variable of dumb tropical climate. This paper revisits the hydroclimatic changes of the Ubangui River at the outlet of Bangui in favor of a new hydropluviometric serial data from 1935 to 2015. The annual rainfall and hydrological data series were analyzed using different statistical tests (rainfall index and flow index, breaks research, depletion coefficients). Rainfall series still shows only one break in 1970, which confirms the exceptionality of this climate disruption in Central Africa. However hydrological series identifies four different hydrological periods: 1935-1959, 1960-1970, 1971-1982 and 1982-2013. The last period shows an average deficit of -22% (2 893 m(3)/s) compared to the mean annual flow over the entire study period (3 700 m(3)/s). The average relationship rain/runoff did not change during these well-identified hydroclimatic periods, suggesting that the hydrological functioning of the Ubangui River has not changed because of this climate disruption. It is attributed to the low human impact over this basin and to the small change of the vegetation cover. However the comparison of annual changes in the depletion coefficient with the volume mobilized by the aquifer flows to sustain the Ubangui River flows clearly indicates the relationship change before and after 1970 and after 2000.Ce papier revisite l'évolution hydroclimatique de l'Oubangui à Bangui à la faveur d'une nouvelle série hydropluviométrique de 1935 à 2015. Pour cela, les données annuelles pluviométriques et hydrologiques de l'Oubangui à Bangui ont été analysées avec différents tests statistiques (indices pluviométrique et d'écoulement, recherches de ruptures, coefficients de tarissement). La série pluviométrique n'indique toujours qu'une seule cassure en 1970, ce qui confirme l'exceptionnalité de cette rupture climatique en Afrique Centrale. Par contre, la série hydrologique permet d'identifier quatre périodes hydrologiques différentes : 1935-1959, 1960-1970, 1971-1982 et 1982-2013. La dernière période montre un déficit moyen de -22 % (2 893 m3/s) par rapport au débit moyen annuel sur toute la période étudiée (3 700 m3/s.). Les relations moyennes pluie/débit n'ont pas évolué au cours de ces périodes hydroclimatiques, semblant indiquer que le fonctionnement hydrologique de l'Oubangui n'a pas changé du fait de la rupture climatique de 1970. Cela est attribué à la faible anthropisation de ce bassin et la faible évolution de son couvert végétal. Cependant la comparaison de l'évolution annelle du coefficient de tarissement avec le volume mobilisé par l'aquifère pour soutenir les écoulements de l'Oubangui indique clairement un changement de contribution de la nappe avant et après 1970, puis après 2000