Evaluation de la pollution métallique des eaux souterraines et de surface dans un environnement minier aurifère à Hiré (Côte d’Ivoire)

Cette étude a pour objet l’évaluation du taux de pollution métallique des eaux souterraines et de surface dans un environnement minier. Pour y parvenir, des prélèvements d’eaux ont été effectués au cours de deuxcampagnes d’échantillonnage (mois décembre 2012 et mois de février 2013) dans la Sous-préfecture de Hiré (centre ouest de la Côte d’Ivoire). Les résultats ont montré des concentrations élevées pour tous les paramètres métalliques dans la majorité des stations. En effet, les teneurs d’arsenic, de cadmium, de mercure, de nickel, de plomb sont largement supérieures aux valeurs limites fixées par l’OMS pour les eaux de consommation et  d’irrigation. En outre, elles pourraient constituer des risques sanitaires pour la population de la zone d’étude. Nos résultats serviront de base aux politiques environnementales nationales visant à protéger les populations vivant dans un environnement minier.Mots clés : Pollution, métaux, sols, Hiré, Côte d’Ivoire

Impact des pressions anthropiques sur la flore de la forêt classée du Haut-Sassandra (Centre-ouest de la Côte d'Ivoire)

Impact of Anthropogenic Pressures on the Flora of the Haut-Sassandra Classified Forest (Central-West of Côte d'Ivoire). The classified forest of Haut-Sassandra located in the center-west of Ivory Coast is subjected to a strong anthropization since the politico-military conflicts of the year 2002. This study aims to quantify the degradation in the northern, central and southern zones of this domain. To achieve this, a spatiotemporal analysis of the dynamics of the three zones was made based on five Landsat images from 1990, 1997, 2002, 2006 and 2013. It was supplemented by a floristic inventory of each zone. The results show that forest cover conversions of the three zones occurred during the conflict period with regression rates of more than 50 %. At the floristic level, 622 plant species distributed among 410 genera and 104 families were recorded in all three zones. The North and the Center differ significantly from the South by the average specific richness. The inventoried flora generally differs from one zone to another depending on the degradation factors, with a greater diversity in cocoa plantations. However, this flora, although diversified, does not have any similarity with that of the forest relics still present in the classified forest of Haut-Sassandra

Saturation foncière à la périphérie de la Forêt Classée du Haut-Sassandra (Centre-Ouest de la Côte d'Ivoire) durant la période de 1990 à 2016

Land Saturation at the Periphery of the Haut-Sassandra Classified Forest (Central-West of Ivory Coast) During the Period 1990 to 2016. The Haut-Sassandra Classified Forest (FCHS) experienced an accelerated deterioration with the 2002 crisis that shook Ivory Coast. The establishment of crops and habitats within this forest may suggest that the land on the periphery of this forest would be depleted. However, studies dealing with land saturation in the area around this FCHS are almost non-existent. The purpose of this study is to determine the dynamics of land use and land management in the peripheral zone of the FCHS. To achieve this, five Landsat satellite images covering the period 1990 to 2016 were acquired and processed. The validation of these treatments was coupled with socio-economic surveys and participatory observations carried out in 11 villages bordering this forest. The various analyzes show that perennial crops, mainly cocoa trees, already occupied 73.9% of the area in 1990. With the disappearance of forests, aging orchards and certain parasitic constraints, cocoa cultivation experienced a regression during and after the decade of crisis in favor of rubber and cashew nuts. All this affects the land acquisition methods dominated before the crisis by donation or leasing but witch have disappeared today to the benefit of inheritance and purchase

Analyse des profils écologiques des produits forestiers non-ligneux dans la région du Haut-Sassandra (Centre-Ouest de la Côte d'Ivoire)

Distribution of non-timber forest products in an environment submitted to strong anthropogenic pressures in the periphery of the Classified Forest of Haut-Sassandra (Central-West Côte d'Ivoire). The population of the Classified Forest Haut-Sassandra (FCHS) regularly uses Non-Timber Forest Products (NTFP) for several purposes. Unfortunately, the degradation of natural ecosystems observed in recent decades in and around the FCHS following the different crises experienced by Ivory-Coast has modified the availability of certain NTFP. For a sustainable exploitation of these NTFP, this study evaluates the ecological and human factors which could affect the distribution of six NTFP deemed to have priority around the FCHS. To achieve this aim, investigations and field surveys were conducted in 11 villages along the FCHS. In order to see the links between the different factors identified, a multiple factor analysis was carried out and then supplemented by tests of frequency analysis. The results indicate that Ricinodendron heudelotii, Irvingia gabonensis, Entandrophragma angolense and Milicia excelsa occur in all types of environment and at various distances from the villages. One species, Neuropeltis acuminata is forest-dependent and Laccosperma secundiflorum occurs exclusively in the shallows. The latter two species are likely to disappear from the village territory due to the intensification of anthropogenic activities observed in recent decades in the area

Pratique cacaoyère, délitement de l'accès au foncier et sécurité alimentaire dans la sous-préfecture de Dania (centre-ouest de la Côte d'Ivoire)

Cocoa Cultivation, Disintegration of Land Access and Food Security in the Sub-prefecture of Dania (Center-west of Côte d'Ivoire). The cocoa plantations are exponentially increasing and most of the rural households in the forest area of Ivory Coast are involved in it. In the sub-prefecture of Dania, 77.7% of the households have a cocoa exploitation. Currently, the cocoa plantations in the area of Dania are facing a production crisis which is amplified by the military political crisis of September 2002. The incomes of the producers of cocoa are decreasing. Because of the great impact of the cocoa production on farm land, the available area to fulfill the food needs becomes insufficient. Forty three percent of the households lack sufficient land to satisfy their food production. The minimum period of seven year of fallow being no longer respected soil fertility problems are created and consequently a decrease of the agricultural yields. Fifty seven percent of the households are facing food insecurity. Therefore, the households have elaborated new strategies for land appropriation, such as the borrowing of farm land (13 %), the increased use of the phytosanitary products (52%) and particularly the higher attraction for the exploitation of fallow land (40%)

Influence of forest degradation on tree diversity in a forest-savannah transition in Eastern Ivory Coast

This study aimed at determining forest degradation impact on tree diversity in a forest-savannah transition zone in Ivory Coast. Structures of forest patches were given from the comparison of their number, area and index of fragmentation on basis of two land cover maps. Two forest types were identified according to their degradation. Results showed that landscape and forest disturbance, characterized by a forest canopy opening up, led to an increase of light-tolerant species and their richness in degraded forests. Thus, if diversity is summarized to species richness, forest degradation does not lead to a reduction of diversity. In contrast,species in degraded forests are less evenly distributed than those in non-degraded forests. Species abundance distribution in degraded forests indicates that only a few species dominate this zone due essentially toanthropogenic disturbances. In non-degraded forests, abundance distribution shows a relatively stable community in which individuals are more evenly distributed among species. Considering species abundancedistribution and evenness index, non-degraded forest has a greater diversity than degraded forest

Partition du territoire et dynamique des végétations pendant la période de conflit en Côte d'Ivoire

Country Partition and Vegetations Dynamics During the Period of Conflict in Côte d'Ivoire. The political-military crisis in Ivory Coast started in September 2002 led to a partition of the country into two distinct military and administrative entities. The South remained under governmental control when the north of the country was under the management of an armed rebellion; these two entities being separated by the so-called buffer zone. Apart from the repercussions on the population, this crisis has led to disturbances in the landscape. The present study consisted of highlighting the spatio-temporal dynamics of the national parks and classified forests located in each of the three cutting zones of the country between 2002 and 2013. The land use maps were made at the beginning and at the end of conflicts. An anthropogenic disturbance index quantified the disturbances in the different settings. The results showed that the impact of the crisis was more pronounced in the formations belonging to the forest areas than in the savannah zones. According to the territorial division resulting from the crisis, it was the so-called buffer zone which was the most disturbed. Moreover, the formations located in the centre-west, zone of high cocoa production, have suffered the most severe disturbances

Dynamique paysagère de la Forêt Classée de la Lama au sud du Bénin

Landscape Dynamics of the Classified Forest of Lama in Southern Benin. The Lama (South Benin) classified forest has undergone profound changes as a result of the restoration and conservation efforts that need to be quantified using landscape ecology techniques and phytosociology. Aiming to map land cover and to evaluate landscape dynamics we assessed two Landsat images (2000 Landsat ETM+ and 2015 Landsat OLI TIRS), using transition matrix and decision tree algorithm model. Phytosociological inventories were carried out to assess the conservation status of the classified forest from 80 records on a transect of 50 m long and 10 m wide. Analyzes show that in 2015 the forest covers 27.85% of the landscape compared with 8.02% in 2000, to the detriment of anthropogenic classes after management. The main spatial transformation processes in the landscape were aggregation, creation and attrition. Phytosociological classification showed two physiognomic vegetation groups based on 192 species. These groups are specifically diversified with the predominance of species from the Guinea-Congolese base-element which confirms acceptable conditions in the forest

Diversité et distribution d'abondances des plantes d'un écosystème protégé dans un paysage anthropisé: cas de la Réserve Naturelle Forestière de Bururi, Burundi

info:eu-repo/semantics/publishe

Distribution spatiale intra-urbaine des particules fines : monitoring par l’Aimantation Rémanente Isotherme à Saturation des feuilles (SIRM) en milieu tropical urbain (Côte d’Ivoire).

Objectif: Le présent travail vise à déterminer les teneurs en particules fines à partir de l’Aimantation Rémanente Isotherme (SIRM) des feuilles de plantes tropicales dans le District d’Abidjan.Méthodologie et résultats : Des échantillons de feuilles de plantes de Amaranthus spinosus, Panicum maximum, Ficus benjamina et Terminalia catappa ont été prélevés dans différents types d’utilisation du sol que sont : les axes routiers ; les zones industrielles ; les zones résidentielles et les parcs et jardins. Les valeurs les plus élevées de SIRM (22,33 x10-5A et 7, 36 x10-5A) ont été enregistrées avec les feuilles de Amaranthus spinosus respectivement en zones industrielles et au niveau des axes routiers. Au contraire, dans les zones résidentielles et les parcs et jardins, les SIRM des feuilles sont très faibles avec des valeurs variant entre 2,62 x10-5A et 0,33 x10-5A au cours des différentes saisons. Les résultats ont révélé également un gradient croissant des SIRM des feuilles à mesure que l’on se rapproche des routes et un gradient décroissant avec la hauteur d’échantillonnage. En outre, l’accumulation des particules fines est faible pendant un mois pluvieux par rapport à un mois sec.Conclusion : Les résultats de cette étude ont permis de ranger les types d’utilisation du sol étudiés en deux catégories selon la qualité de l’air. Ainsi les zones industrielles et les abords des principaux axes routiers sont des zones de mauvaise qualité d’habitat car plus pollués que les zones résidentielles et les parcs et jardins qui sont des zones de bonne qualité d’habitat. Aussi, cette étude a révélé que les principales sources de la pollution de l’environnement en milieu urbain sont d’une part les émissions des gaz d’échappement des véhicules et d’autre part les cheminées des usines. En somme, le SIRM des feuilles des plantes peut être utilisé comme un bio-indicateur de la qualité de l’air dans un environnement urbain en milieu tropical.Mots clés : biomonitoring, particules fines, Aimantation Rémanente Isotherme à Saturation (SIRM), qualité de l’habitat, plantes tropicale