Kpérkouma Wala

Satellite monitoring of land-use and land-cover changes in northern Togo protected areas

Remote-sensing data for protected areas in northern Togo, obtained in three different years (2007, 2000, and 1987), were used to assess and map changes in land cover and land use for this drought prone zone. The normalized difference vegetation index (NDVI) was applied to the images to map changes in vegetation. An unsupervised classification, followed by classes recoding, filtering, identifications, area computing and post-classification process were applied to the composite of the three years of NDVI images. Maximum likelihood classification was applied to the 2007 image (ETM+2007) using a supervised classification process. Seven vegetation classes were defined from training data sets. The seven classes included the following biomes: riparian forest, dry forest, flooded vegetation, wooded savanna, fallows, parkland, and water. For these classes, the overall accuracy and the overall kappa statistic for the classified map were 72.5% and 0.67, respectively. Data analyses indicated a great change in land resources; especially between 1987 and 2000 probably due to the impact of democratization process social, economic, and political disorder from 1990. Wide-scale loss of vegetation occurred during this period. However, areas of vegetation clearing and regrowth were more visible between 2000 and 2007. The main source of confusion in the contingency matrix was due to heterogeneity within certain classes. It could also be due to spectral homogeneity among the classes. This research provides a baseline for future ecological landscape research and for the next management program in the area.

La végétation de la chaîne de l'Atakora au Bénin: diversité floristique, phytosociologie et impact humain

à l’Université de Lomé (Togo), Faculté des Sciences, sous la direction du Pr Koffi Akpagana et la co-direction de Brice Sinsin, pour l’obtention du grade de docteur de l’Université de Lomé, spécialité botanique et écologie végétale, devant le jury suivant : Messanvi Gbeassor (Université de Lomé, Togo), Kouami Kokou (Université de Lomé, Togo), Koffi Akpagana (Université de Lomé, Togo) et Brice Sinsin (Université d’AbomeyCalavi).

Quick numerical assessment of plant communities and land use change of Oti prefecture protected areas (North Togo)

In this paper, the analysis of Land sat images and plant ecological assessment were used to determine the land use change, plant diversity and the main plant community patterns in most environmentally disturbed areas of northern Togo. Floristic data in the survey areas were collected using transect and sampling methods which were both based on Braun Blanquet phytosociology concept. Several numerical processes were then retained to analyze the floristic data such as Detrended Correspondence Analysis (DCA), Hierarchical Clustering and Indicator Value (INDIVAL). The first two analyses were to define the plant groupings while the third was to name the plant communities found. The logical technique of RGB-NDVI suggested by Sader and Winne as an essential tool for land use assessment was applied to remote sensed data covering three time periods (1987, 2000 and 2007). The Normalized Difference Vegetation Index (NDVI) was then applied to both images after atmospheric correction before stacking them to obtain a RGB_NDVI composite image. Finally an unsupervised classification followed by post-classification process was applied to the RGB_NDVI image. All the results from these analyses show that seven plant groupings can be found in this area which mostly represents the physiognomy of shrubby savanna. The most frequent, abundant and typical plant species to Sudanian area are Terminalia laxiflora, Crotalaria graminicola, Vitellaria paradoxa. Great mutations in land use change are well perceptible after analysis. In overall the harvest of plant resources was higher between 1987 and 2000 while the regrowth of biomass was limited and unequal. The areas characterized with biomass clean and or regrowth is well represented in term of superficies, which denote the level of anthropogenous disturbance factors prevailing in this zone. However, there are certain zones where changes have not happened yet such as a few dimensions in riparian forests, though according to the field observations these riparian forests and their neighboring wooded vegetation are very disturbed. The rivers, pounds, barren lands and the scattered villages are also considered as no change areas.

Assessment of multifunctional landscapes dynamics in the mountainous basin of the Mo River (Togo, West Africa)

In this study, historical landscape dynamics were investigated to (i) map the land use/cover types for the years 1972, 1987, 2000 and 2014; (ii) determine the types and processes of landscape dynamics; and (iii) assess the landscape fragmentation and habitat loss over time. Supervised classification of multi-temporal Landsat images was used through a pixel-based approach. Post–classification methods included systematic and random change detection, trajectories analysis and landscape fragmentation assessment. The overall accuracies (and Kappa statistics) were of 68.86% (0.63), 91.32% (0.79), 90.66% (0.88) and 91.88% (0.89) for 1972, 1987, 2000 and 2014, respectively. The spatio-temporal analyses indicated that forests, woodlands and savannahs dominated the landscapes during the four dates, though constant areal decreases were observed. The most important dynamic process was the decline of woodlands with an average annual net loss rate of–2%. Meanwhile, the most important land transformation occurred during the transition 2000–2014, due to anthropogenic pressures. Though the most important loss of vegetation greenness occurred in the unprotected areas, the overall analyses of change indicated a declining trend of land cover quality and an increasing landscape fragmentation. Sustainable conservation strategies should be promoted while focusing restoration attention on degraded lands and fragmented ecosystems in order to support rural livelihood and biodiversity conservation.

Modelling soil erosion response to sustainable landscape management scenarios in the Mo River Basin (Togo,West Africa)

The rural landscapes in Central Togo are experiencing severe land degradation, including soil erosion. However, spatially distributed information has scarcely been produced to identify the effects of landscape pattern dynamics on ecosystem services, especially the soil erosion control. In addition, relevant information for sustainable land and soil conservation is still lacking at watershed level. On this basis, using the LAndscape Management and Planning Tool for the Mo River basin (LAMPT_Mo), we (1) modelled soil erosion patterns in relation with land use/cover change (LUCC), land protection regime, and landforms, and (2) examined the efficiency of landscape redesign options on soil erosion amounts at basin scale. We found that Simulated historical net soil loss (NSL) for the Mo basin were approximately 26, 23, 27, and 44t/ha/yr, for 1972, 1987, 2000, and 2014, respectively. These simulated NSLs were higher than the tolerable soil loss limits for the Tropics. Steep slopes (≥15°), poorly covered lands (croplands and savannas), and riversides (distances ≤100m) are critical areas of sediment sources. The local appraisal of soil loss was in line with the simulated outputs even though quantification was not accounted for when dealing with rural illiterate people. Furthermore, results showed that the examined management measures, such as controlling the identified erosion hotspots through land protective measures, could help reduce the NSL up to 70%, to values closer to the tolerable limits for the Tropics. The model implementation in the basin showed insights for identifying erosion hotspots and targeting soil conservation planning and landscape restoration measures.

Spatio-Temporal Dynamics in Land Use and Habitat Fragmentation within a Protected Area Dedicated to Tourism in a Sudanian Savanna of West Africa

Abstract Nazinga Game Ranch (NGR) is a reserve in Burkina Faso involving local communities for securing biodiversity through sustainable management. Yet, its ecosystems are threatened by increasing number of elephants and illegal human activities. Renowned as a model of wildlife participatory management, NGR has mainly been studied for its animal wildlife only. The aim of this study was to uncover ecological effects of recent land management on savanna habitats including tourism, and to conclude on more sustainable options, land use/land cover (LULC) changes and vegetation dynamics in NGR were analyzed. This was accomplished with multi-temporal change detection using Landsat images of 1984, 2002 and 2013 to map seven representative LULC classification categories, and quantitative indices of landscape metrics. The results showed that the LULC dynamics in NGR from 1984 to 2013 was mainly characterized by an expansion of gallery forest, tree savanna and agricultural area and a reduction of shrub savanna, woodland and bare soils. From 2002 to 2013, fragmentation in all land cover types increased at the landscape level, whereas at the class level, it decreased for woodland. Our findings provided evidence of habitat degradation in NGR, due to extensive agriculture, tourism and growing of elephants’ population. According to the original management goals and the purposes of the reserve, both fauna and tourism are to be maintained and sustained in a sustainable way. Adaptation of land use and targeted wildlife management are the main requirements for avoiding further degradation of vegetation and thus of the existence basis of local inhabitants, animals and tourism.

Land cover changes assessment using object‐based image analysis in the Binah River watershed (Togo and Benin)

In this study, land cover changes between 1972 and 2013 were investigated in the Binah River watershed (North of Togo and Benin) using remote sensing and geographic information system technologies. Multitemporal satellite images—Landsat MSS (1972), TM (1987), and OLI-TIRS (2013)—were processed using object-based image analysis and post–classification comparison methods including landscape metrics and changes trajectories analysis. Land cover maps referring to five main land cover classes, namely, agricultural land, forest land, savannah, settlements, and water bodies, were produced for each acquisition date. The overall accuracies were 76.64% (1972), 83.52% (1987), and 88.84% (2013) with respective Kappa statistics of 0.69, 0.78, and 0.86. The assessment of the spatiotemporal pattern of land cover changes indicates that savannah, the main vegetation type, has undergone the most dominant change, decreasing from 67% of the basin area in 1972 to 56% in 1987 and 33% in 2013. At the same time, agricultural land has significantly increased from 15% in 1972 to 24% in 1987 and 43% in 2013, while some proportions of agricultural land were converted to savannah relating to fallow agriculture. In total, more than 55% of the landscape experienced changes between 1972 and 2013. These changes are primarily due to human activities and population growth. In addition, agricultural activities significantly contributed to the increase in the number of patches, degree of division, and splitting index of forest and savannah vegetations and the decrease in their effective mesh sizes. These results indicate further fragmentation of forest and savannah vegetations between 1972 and 2013. Further research is needed to quantitatively evaluate the influences of individual factors of human activities and to separate these from the impacts of climate change-driven disturbances.

Études biochimiques et évaluation des valeurs nutritionnelles de quelques espèces alimentaires mineures du Togo

Abstract The aim of this study is to assess biochemical and nutritional values of some lesser used food crops in Togo. It shows that some of these species have real and interesting nutritive values for some vulnerable people such as children, women, convalescent and old persons.

Changes in Land Cover Categories within Oti-Kéran-Mandouri (OKM) Complex in Togo (West Africa) between 1987 and 2013

Oti-Keran-Mandouri (OKM) is a complex of protected areas with national and international ecological importance. It is located in the flood plain of the Oti River in Togo. Unfortunately, this area is under anthropogenic pressure. In order to enhance biodiversity conservation, this study aims to assess the spatial changes in land cover within OKM. Landsat images from different missions spanning the time steps 1987, 2000 and 2013 were used to produce land cover maps involving six classes. The classification was based on the maximum likelihood algorithm and the change analyses were performed using Land Change Modeler software integrated in Idrisi GIS and Image Processing system. From 1987 to 2013, wetlands, forests and savannahs diminished while cropland and settlements expanded. Considering the overall area of OKM, wetlands decreased from 43.05 % in 1987 to 31.71 % in 2013. Meanwhile, croplands increased from 0.91 % in 1987 to 34.81 % in 2013. Considering their earlier areas in 1987, forests, savannahs and wetlands have experienced an average annual loss of 5.74 %, 3.94 % and 2.02 %, respectively, while croplands increased at an average annual rate of 285.39 %. The main drivers of these changes appear to be the inadequacy of the management system and increasing anthropogenic pressures. These are intensified by climate change since adaptive strategies, such as recessional agriculture, play an important role in land cover change. The ongoing process of rehabilitation should be strengthened to enable this protected area to play its roles as Ramsar site, biosphere reserve and priority corridor for the migration of the West African savannah elephant. Data from this study could be used to guide conservation planning, further landscape pattern assessment and land cover modelling in the framework of climate change.

Long term evaluation of green vegetation cover dynamic in the Atacora Mountain chain (Togo) and its relation to carbon sequestration in West Africa

The research was done in the Atacora Mountain chain in Togo which tended to assess the change of vegetation cover during a 24-year period. It also aims to evaluate the dynamic of the net primary productivity (NPP) of the living plants over the same period. The Landsat imagery covering three different periods (1987, 2000, and 2011) was pre-processed to correct atmospheric and radiometric parameters as well as gapfilling the 2011 SCL-off images. Then, the vegetation indices such as NDVI (normalized difference vegetation index), SR (simple ratio vegetation index), SAVI (soil-adjusted vegetation index), and CASA (carnegie- ames- stanford approach)model for NPP were applied on these images after masking the study area. The results showed a quiet decrease in the vegetation cover. The vegetation loss was more significant from 2000 to 2011 than from 1987 to 2000, and anthropogenic activities can be deemed as the main cause of the vegetation loss. The biomass assessment by NPP computation also showed a decrease over the time. Similar to the change of the vegetation cover, the ecosystem net productivity was very low in 2011 compared to 2000 and 1987. It seems that the general health condition of the vegetation, including its potentiality in carbon sinking, was negatively affected in this area, which has already been under threatened. A perpetual monitoring of these ecosystems by means of efficient techniques could enhance the sustainable management tools of in the framework of reducing emissions from deforestation and forest degradation (REDD).