DYNAMIQUE DES FORMATIONS FORESTIÈRES DE LA HAUTE-CASAMANCE (SÉNÉGAL) DE 1965 A 2018, INCIDENCES SUR LES ACTIVITÉS AGRO-SYLVO-PASTORALES ET STRATÉGIES D’ADAPTATION
| Autor: | SOLLY, BOUBACAR |
|---|---|
| Přispěvatelé: | SOLLY, BOUBACAR, Laboratoire de Géomatique et d’Environnement (LGE), Université Assane SECK de Ziguinchor (UASZ), Université Assane Seck de Ziguinchor (Sénégal), Oumar Sy, El Hadji Balla Dieye |
| Jazyk: | francouzština |
| Rok vydání: | 2021 |
| Předmět: |
Dynamique
[SDE] Environmental Sciences Flore ligneuse Télédétection Déforestation [SHS.GEO] Humanities and Social Sciences/Geography Haute-Casamance [SHS.GEO]Humanities and Social Sciences/Geography Savanisation Remote sensing Formations forestières Senegal Dynamics Anthropisation Sénégal Agricultural-forestry-pastoral Upper Casamance Agro-sylvo-pastorales [SDE]Environmental Sciences Deforestation Plant formations Anthropization Woody flora |
| Zdroj: | Géographie. Université Assane Seck de Ziguinchor (Sénégal), 2021. Français |
| Popis: | The forest landscapes of southern Senegal, particularly Upper-Casamance, are increasingly subject to deforestation. The result is a strong tendency to "savanisation" and anthropization, hence the major concern of the Senegalese authorities to take charge of the problem. Faced with such a situation, the study of the dynamics of forest formations in Upper-Casamance becomes relevant for a sustainable management of forest resources. This study aims to map and quantify the evolution of forest formations between 1965 and 2018, and to analyze the main determinants of dynamics and impacts on agro-sylvo-pastoral activities, wildlife and woody flora.The methodological approach is based on the processing and analysis of aerial (Corona 1965) and satellite images [Landsat (TM 1987, ETM+ 1999, TM 2010 and OLI-TIRS 2018), Sentinel 2 (MSI 2018) and MODIS-NDVI (2000 to 2018)]. It is also based on the processing and analysis of hydro-climatic data and the collection of field data (field observations, GPS point surveys, household surveys and population perception).The results showed a significant savanisation and development of agricultural land. Indeed, forest formations lost 377 118.7 ha of their area between 1987 and 2018, or a deforestation rate of 62.04%. Woodlands and agricultural land increased by 263,172.4 ha (19.1%) and 147,178.2 ha (10.7%) respectively over the same period. Significant negative trends in NDVI indicated vegetation degradation along the Gambia border, along the Pata-Ndorna axis, in the centre of the study area and around Medina Gounass. On the other hand, significant positive trends (p0.1) indicate regeneration in the south. The percentage of significant positive trend (at the 10% threshold) is 1.8%; the significant negative trend is 2.1%. At the scale of classified forests and managed forests, great variability by domain, the geographic position and rainfall gradient was noted. This variability has shown that classified forests are much more affected by anthropogenic actions than managed ones. The analysis of the factors behind the dynamics has shown that man, through agricultural clearing, bush fires, abusive and illicit cutting of wood for various reasons, stand, land use patterns, and extensive livestock rearing, is the main factor of deforestation, extension of savanna and fragmentation of landscapes. He also played a role in regeneration. Similarly, the variability of hydro-climatic conditions has also played a role in savanisation and regeneration. This dynamic, as well as the explanatory factors, have caused, among other things, impacts on agricultural, forestry and pastoral activities, water erosion and silting of rice fields, the decline in the fertility of cultivable soils and yields. They are also reflected in the scarcity of wild fruit, the reduction of pasture areas which are increasingly being converted into cultivation areas, the reduction of fodder in the dry season and of particularly well-adapted species, the early drying up of ponds and the scarcity or even disappearance of certain animal and plant species. Les paysages forestiers du Sud du Sénégal, particulièrement de la Haute-Casamance, font de plus en plus l’objet de déforestation. Il en résulte une forte tendance à leur "savanisation" et anthropisation, d’où la préoccupation majeure des autorités sénégalaises à prendre le problème en charge. Devant une telle situation, l’étude des dynamiques des formations forestières de la Haute-Casamance devient pertinente pour une gestion durable des ressources forestières. Cette étude vise à cartographier et à quantifier l’évolution des formations forestières entre 1965 et 2018, et à analyser les principaux déterminants des dynamiques et incidences sur les activités agro-sylvo-pastorales, la faune sauvage et la flore ligneuse.La démarche méthodologique s’appuie sur le traitement et l’analyse d’images aériennes (Corona 1965) et satellitaires [Landsat (TM 1987, ETM+ 1999, TM 2010 et OLI-TIRS 2018), Sentinel 2 (MSI 2018) et MODIS-NDVI (2000 à 2018)]. Elle se base également sur le traitement et l’analyse de données hydro-climatiques et sur la collecte de données sur le terrain (observations de terrain, levés de point GPS, enquêtes-ménages et perception des populations).Les résultats ont montré une savanisation et un développement important des surfaces agricoles. En effet, les formations forestières ont perdu 377 118,7 ha de leur superficie entre 1987 et 2018, soit un taux de déforestation de 62,04%. Les formations boisées et les surfaces agricoles ont augmenté respectivement de 263 172,4 ha (soit 19,1 %) et 147 178,2 ha (soit 10,7 %) durant la même période. Des tendances négatives significatives du NDVI ont indiqué une dégradation de la végétation le long de la frontière avec la Gambie, sur l’axe Pata-Ndorna, dans le centre de la zone d’étude et autour de Médina Gounass. Par contre, des tendances positives significatives (p |
| Databáze: | OpenAIRE |
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