Influence des Pressions Anthropiques sur la Dynamique Paysagère de la Reserve Partielle de Faune de Dosso (Niger)

Abstract

RESUMELa Réserve Partielle de Faune de Dosso est une aire protégée à statut de zone tampon du parc national du W du Niger. De sa création (1962) à aujourd'hui, la réserve est devenue l'espace d'accueil des réfugiés écologiques (migrants agricoles et éleveurs peulhs) du Niger et des pays limitrophes. Une destruction massive de son potentiel ligneux et faunique a été observée ces trois décennies, décriées par les gestionnaires forestiers. Cette étude vise à analyser la dynamique du paysage de la réserve couvrant la période 1986 à 2016. Les images Landsat 5 TM (1986) et Landsat 8 OLI (2016) ont servi de source de données pour cette étude. La classification supervisée par maximum de vraisemblance et le calcul d'indices écologiques ont permis de quantifier la dynamique d'occupation du sol et de détecter les transformations spatiales survenues en 30 ans, au moyen des logiciels ENVI 7.1 et Arcgis 10.2. Les résultats montrent globalement une forte progression des classes d'occupation du sol champs-jachères et sols nus contre une nette régression des classes de formations forestières naturelles. Les transformations spatiales en cours sont la fragmentation, la dissection et la perforation des classes de végétation naturelle. Cette étude a permis de mettre en lumière les processus de transformation spatiale en cours dans le paysage de la réserve et de déterminer les indicateurs d'état pouvant servir de base à la gestion et à la conservation des ressources forestières de la réserve de partielle de faune de Dosso au Niger. ABSTRACTThe Dosso Wildlife Reserve is a protected area with buffer zone status in Niger's W National Park. From its creation (1962) to today, the reserve has become the reception area for environmental refugees (agricultural migrants and Fulani pastoralists) from Niger and neighboring countries. A massive destruction of its ligneous I. K. ABDOU et al. / Int. J. Biol. Chem. Sci. 13(2): 1094-1108, 2019 1095 and faunal potential has been observed these three decades, decried by the forest managers. This study aims to analyze the landscape dynamics of the reserve covering the period 1986 to 2016. The Landsat 5 TM (1986) and Landsat 8 OLI (2016) images served as a data source for this study. Maximum likelihood-based classification and ecological index computation were used to quantify land cover dynamics and to detect spatial transformations over 30 years using ENVI 7.1 and Arcgis 10.2 software. Overall, the results show a sharp increase in land-fallow and bare soil occupation classes against a clear regression of the natural forest formation classes. The spatial transformations in progress are fragmentation, dissection and perforation of the vegetation classes natural. This study shed light on the spatial transformation processes underway in the reserve landscape and to determine the state indicators that can be used as a basis for the management and conservation of the forest resources of the partial wildlife reserve from Dosso to Niger.

Hydrological Factor and Land Use/Land Cover Change Explain the Vegetation Browning in the Dosso Reserve, Niger

“…The western Dosso Reserve is crossed by the Niger River, close to the Niger River valley and Niamey, the capital city of Niger. The Dosso Reserve was established in 1962 and protects a wide range of wildlife species and habitats from the W National Park and adjacent areas [8,25]. This area is the center of the Sahel-Sudan region with a typical tropical climate condition.…”

“…This region has a significant climate gradient from north to south, with average annual precipitation ranging from less than 500 mm in the northern areas to more than 800 mm in the southern areas. The main vegetation cover types in this region are grass, shrub, tiger bush (a typical banded vegetation pattern of trees and bushes), and savanna [25]. The boundary of the Dosso Reserve was obtained from the World Database on Protected Areas (WDPA, https://www.protectedplanet.net/11652, accessed on 31 January 2024).…”

“…In general, an increase in grassland fraction and a decrease in fractions of shrubland and forest would reduce NDVI values. In the Dosso Reserve and surrounding areas, agriculture and grazing are the main productive activities to meet the increasing demands of population growth, which led to the widespread conversion of grassland, shrubs, and forests into cropland and pastures [14,18,25,64]. In addition, the Dosso Reserve is the main source of firewood supply and medicinal materials for the surrounding areas, and unsustainable wood extraction led to its degradation [65][66][67].…”

“…The Dosso Partial Faunal Reserve in Niger (hereinafter referred to as "the Dosso Reserve"), as an functional zone of the W National Park, is a typical Sahelian-Sudano savanna ecosystem that provides essential habitat for a wide range of wildlife species, both resident and migratory [24]. Land degradation and habitat fragmentation linked to climate change and human activities pose a significant challenge to wildlife populations in the Dosso Reserve [25]. In the context of regional environmental change, it is important to continuously and thoroughly investigate the vegetation dynamics and potential drivers in the protected areas and their adjacent regions.…”

Tendances évolutives des paysages semi-arides anthropisés au Niger: cas des communes rurales d’Aguié, Tchadoua et Gangara (Région de Maradi)

“…Il se répercute sur la composition et la configuration du paysage (Touré, 2010). Ainsi, au Sahel et au Niger en particulier, la répartition déséquilibrée dans l'espace et dans le temps des précipitations dont découle la récurrence des sécheresses (Ozer et al, 2010) constitue l'une des principales causes de changements d'occupation/utilisation des terres induisant une transformation significative de la structure et de la composition du paysage (Ibro et Assoumane, 2009 ;Viéri et al, 2008 ;Diallo et al, 2011 ;Millogo et al, 2017 ;Abdou et al, 2019). En outre, les importants bouleversements environnementaux observés actuellement résultent également du déboisement incontrôlé et de l'expansion agricole (Ozer et al, 2010).…”