Dynamique spatio-temporelle du couvert forestier dans le bassin de la rivière Kara au Nord Togo (Afrique de l’Ouest)

Cette étude examine l'évolution de l'occupation des sols dans le bassin de la Kara sur 50 ans, de 1972 à 2021, en utilisant des images Landsat. Ce bassin, affecté par l'augmentation de la population, subit des changements notables au niveau de son couvert forestier. L'objectif est d'évaluer la dynamique à travers l'analyse de données de télédétection. Les étapes incluent la cartographie de l'occupation du sol pour les années 1972, 1987, 2005 et 2021, ainsi qu'une prédiction pour 2050 basée sur un scénario tendanciel. Le VHI a été calculé pour suivre la santé de la végétation et sa corrélation avec les paramètres météorologiques. Les résultats montrent une diminution significative des forêts de 1972 à 2005, suivie d'une légère augmentation jusqu'en 2021, indiquant une tendance positive vers la conservation. Cependant, la conversion des savanes en terres agricoles est préoccupante, avec une dégradation rapide de 9,22 % entre 2005 et 2021. L'analyse de la matrice de Markov a permis d'évaluer les probabilités de transition entre les classes d'occupation du sol pour la période 2021-2050, révélant une tendance à une conversion des savanes en forêts. L'analyse de l'indice VHI montre une variabilité interannuelle de la santé de la végétation, avec des conditions humides et sèches alternant entre 1972 et 2005, et une variabilité réduite entre 2005 et 2021. Ces résultats fournissent des bases pour comprendre et anticiper l'évolution des paysages face aux migrations des populations et au développement agricole.   This study examines land use changes in the Kara basin over a 50-year period, from 1972 to 2021, using Landsat imagery. This basin, impacted by population growth, is experiencing notable changes in its forest cover. The aim is to assess this dynamic through remote sensing data analysis. The steps include mapping land use for the years 1972, 1987, 2005, and 2021, as well as making a prediction for 2050 based on a trend scenario. The Vegetation Health Index (VHI) was calculated to track vegetation health and its correlation with meteorological parameters. The results show a significant decrease in forests from 1972 to 2005, followed by a slight increase until 2021, indicating a positive trend towards conservation. However, the conversion of savannas to agricultural land is concerning, with a rapid degradation of 9.22% between 2005 and 2021. The Markov matrix analysis assessed the probabilities of transition between land use classes for the period 2021-2050, revealing a trend towards the conversion of savannas into forests. The VHI analysis indicates interannual variability in vegetation health, with alternating wet and dry conditions between 1972 and 2005, and reduced variability between 2005 and 2021. These results provide a foundation for understanding and anticipating the evolution of landscapes in response to population migrations and agricultural development

Strengthening forest landscape restoration through understanding land use dynamics: case study of Tchamba Prefecture (Togo)

Land use and land cover (LULC) change remains a major concern in many countries. To examine how land is used for increased actions on forest landscape restoration (FLR) issues, this study analyses LULC changes from 1991 to 2022 and predict future patterns for the years 2050 in Tchamba Prefecture, Togo, using remote sensing and the Cellular Automata-Markov modelling technique. Results show that dense forests and gallery forests (18.85%), open forest/woodland (20.17%), and tree and shrub savannah (50.04%) were the predominant classes of the landscape in 1991. However, by 2022, most tree and shrub savannah had been converted to mosaic crop/fallow land (52.27%), open forest/woodland (19.32%), and plantation (7.09%). Thus, between 1991 and 2022, forest area decreased from 89.87% to 48.96%; a 45.52% reduction in coverage. Predictions are that open forest/woodland, tree and shrub savannah will decline, while mosaic crop/fallow land will increase (51.66%). However, slight increases were recorded in plantation (9.43%) and a slight balance in dense forests/gallery forests (16.17%). Consequently, forest area will slightly change between 2022 (48.96%) and 2050 (47.41%). These changes in LULC are associated to socio-economic pressures and political instability in the 1990s. So, the return to stability, the promotion of community forests as a key restoration model, and the valorisation of agroforestry species allows for the stabilisation of dense forests/gallery forests areas and an increase in plantation. Thus, it is therefore for all stakeholders involved in restoration processes to consider this information when planning FLR activities