Spatio‑Temporal Dynamics of Land Cover and Ecosystem Degradation in Madarounfa and Gabi, Niger

 Corresponding author: Karimou Laouali Idi. Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution License 4.0. Spatio‑Temporal Dynamics of Land Cover and Ecosystem Degradation in Madarounfa and Gabi, Niger Karimou Laouali Idi 1, *, Daouda Illia Allo 2, Maman Hassan Abdourazakou 3, Abdoulwahid Sani 4, Karimou Dia Hantchi 5 and Mahamane Moustapha Sanda Chekaraou 6 1 Department of SVT, Abdou Moumouni University, Higher Normal School, Niamey, Niger. 2 Department of Geology, André Salifou University, Faculty of Science and Technology, Zinder, Niger. 3 Department of Geosciences, School of Mines, Industry and Geology of Niamey, Niamey, Niger. 4 Department of Geosciences and Processes, National School of Engineering and Energy Sciences (ENISE), University of Agadez, Agadez, Niger. 5 Department of Geology, Faculty of Science and Techniques, Dan Dicko Dankoulodo University, Maradi, Niger. 6 Department of Didactics of Disciplines, Faculty of Education, Djibo Hamani University, Tahoua, Niger. World Journal of Advanced Research and Reviews, 2025, 28(02), 251-259 Publication history: Received on 07 September 2025; revised on 20 October 2025; accepted on 22 October 2025 Article DOI: https://doi.org/10.30574/wjarr.2025.28.2.3539 Abstract Across the Sahel, the combination of rapid population growth, extensive agriculture, uncontrolled livestock grazing, and high demand for fuelwood has led to accelerated degradation of vegetative resources. This study assesses, through remote sensing (Landsat MSS and 7 imagery) and geographic information systems (GIS), the spatio-temporal dynamics of land cover in the communes of Madarounfa and Gabi (Niger) between 1987 and 2017. Five land cover classes were mapped: water bodies, gallery forests, savanna, steppe, and bare soil. Results reveal severe ecological degradation: savanna declined by 8,752 ha and gallery forest by 9,083 ha, while bare soil expanded dramatically from 47,583 ha to 59,069 ha (57% of the total area). The expansion of the steppe likely reflects the degradation of formerly wooded formations. These changes are attributed to intense anthropogenic pressures including deforestation, agricultural expansion, uncontrolled grazing, and high population density combined with climatic variability, characterised by 17 rainfall-deficient years over a 32-year period. Together, these drivers accelerate desertification, threaten biodiversity, and undermine critical ecosystem services. The study confirms the effectiveness of remote sensing for monitoring landscape change over time and underscores the urgent need to implement integrated strategies for sustainable land management, ecological restoration, and community-based awareness to reverse this critical environmental trend. Keywords: Land Use; Remote Sensing; Degradation; Madarounfa; Gabi 1. Introduction Forests and natural vegetation formations play a fundamental role in maintaining ecological balance and supporting ecosystem functions. They protect soils against erosion, regulate the water cycle, contribute to global carbon cycling, and promote the conservation of plant and animal biodiversity [4], [12]. In the Sahelian region, these formations, particularly savannas and gallery forests, are critical pillars of ecological resilience against desertification and the impacts of climate change [11]. They provide rural populations with essential goods such as fuelwood and non-timber forest products, as well as vital ecosystem services including pollination, microclimate regulation, and soil fertility maintenance [21], [33]. World Journal of Advanced Research and Reviews, 2025, 28(02), 251-259 252 However, these ecosystems face mounting pressures of both anthropogenic and climatic origin [33]. Across the Sahel, the combination of rapid population growth, extensive agriculture, uncontrolled livestock grazing, and high demand for fuelwood has led to accelerated degradation of vegetative resources [7], [1]. In Niger, recent studies indicate a significant decline in woody vegetation, with annual loss rates estimated between 0.5% and 1.2%, depending on the region [2], [14]. This trend is exacerbated by increasing climatic variability, characterised by increasingly erratic rainfall seasons and a rising frequency of droughts [24], [30]. Research conducted in Burkina Faso [20], Senegal [25], and Ethiopia [30] confirms this degradation dynamic, highlighting the widespread conversion of savannas and natural forests into bare soils or degraded agricultural lands. Land cover is the physical appearance of land, representing its ecological status. It is dynamically changed due to human interventions, natural disturbances and successions [30]. Land use/land cover (LULC) changes driven by urbanisation have profoundly influenced habitat quality, threatening ecosystem resilience and biodiversity [32]. Globally, the Global Land Degradation Outlook [34] estimates that one-third of terrestrial land is now degraded, affecting over one billion people. Rapid urbanisation and population growth are amplifying challenges such as urban flooding and the intensification of heat island effects, posing significant risks to cities worldwide [31]. In this context, remote sensing and geographic information systems (GIS) have become indispensable tools for spatio-temporal monitoring of land use and for informing ecological restoration policies [23]. In the communes of Madarounfa and Gabi (Maradi Region, Niger), where population density exceeds 116 inhabitants/km², pressure on natural resources is particularly acute. This study thus contributes to an urgent scientific effort to diagnose spatial and temporal landscape transformations, aiming to generate evidence-based data to support sustainable land management in Sahelian environments. 1.1. Geographical setting The Department of Madarounfa occupies the southernmost part of the Maradi Region, located in south-central Niger. Covering an area of 3,500 km², it represents 9% of the region’s total area, which has a population of 448,863 inhabitants [14]. This is a densely populated area, with a population density exceeding 116 inhabitants per km² [10], concentrated primarily along two valleys: the Goulbi Maradi and the Gabi valleys. Madarounfa lies between 13° and 15° north latitude and 6° and 8° east longitude. It is bordered to the north and west by the Department of Guidan Roumdji, to the east by the Department of Aguié, and to the south by the Federal Republic of Nigeria, with which it shares a border approximately 100 km long [14]. Figure 1 Geographical location of the communes of Madarounfa and Gabi. The study area experiences a Sahelo-Sudanian climate, characterised by a long dry season (8–9 months) and a short rainy season (3–4 months) [13]. The mean annual rainfall recorded between 1984 and 2015 is 501.44 ± 67.18 mm. Mean maximum temperatures during the coolest and hottest months are approximately 14°C and 41°C, respectively. World Journal of Advanced Research and Reviews, 2025, 28(02), 251-259 253 The standard deviation indicates high interannual rainfall variability; indeed, 17 out of the 32 years analysed were rainfall-deficient, approximately one in every two years. Figure 2 Interannual variability of rainfall in the study area from 1987 to 2015. (Meteorological Station at Maradi Airport) 2. Materials and methodological approach 2.1. Data Used This table presents the primary geospatial datasets utilised in this study, along with their formats, spatial resolutions, sources, and specific objectives. Shapefiles at a scale of 1:200,000, provided by the CFDG-Niger, were used to precisely delineate the boundaries of the study area. Landsat 7 satellite imagery (GeoTIFF format, 30 m spatial resolution) and Landsat MSS imagery (GeoTIFF format, 69 m spatial resolution), downloaded via the USGS EarthExplorer platform (https://earthexplorer.usgs.gov ), were employed for land cover mapping. Table 1 Characteristics of satellite data 2.2. Methodology A series of digital image processing operations was conducted to analyse the spatio-temporal dynamics of land use within the study area. Land cover map production began with the identification and acquisition of Landsat scenes corresponding to the Path/Row coordinates covering the communes of Madarounfa and Gabi. Images were downloaded via NASA’s Earth Explorer platform (https://earthexplorer.usgs.gov ) for the years 1987 (Landsat MSS) and 2017 (Landsat 7), prioritising dry-season imagery (mid-September to December) with cloud cover ≤10% to ensure optimal interpretability [27]. Image preprocessing included radiometric correction and filtering using ENVI 5.3 software. Only spectral bands ranging from visible to near-infrared were retained (bands 1, 2, and 3 for MSS; bands 3, 4, and 5 for OLI/TIRS), as these wavelengths provide the most effective spectral discrimination for land cover classes and contain approximately 90% of the spectral information relevant to live vegetation [5], [9], [23]. Image mosaicking was then performed to ensure complete spatial coverage of both communes. False-colour composites were generated to enhance visual discrimination of pixels and facilitate identification of land cover units [15], [25]. World Journal of Advanced Research and Reviews, 2025, 28(02), 251-259 254 Spectral signatures exhibiting uncertainty were geolocated and ground-truthed using GPS field surveys. Digital classification was based on the Yangambi vegetation typology [4] and an interpretative key incorporating site-specific criteria such as geomorphological units, soil texture, laterite crusts, sandstone outcrops, termite mounds, and traces of human activity (e.g., fire scars, grazing patterns), following the Niger NOS land cover nomenclature [18]. Due to the limitations of automated classification methods which are often prone to errors caused by high spectral reflectance variability across land cover types [23], [5] a visual on-screen classification approach was adopted. This method, analogous to supervised classification, involved the manual and exhaustive digitisation of spectrally homogeneous units directly on false-colour composite imagery. This technique significantly improved classification accuracy, particularly for challenging classes to distinguish in Sahelian environments, such as rain-fed agricultural fields. 3. Results and Discussion Based on Landsat imagery acquired from two distinct time periods (1987 and 2017), a comparative analysis was conducted to assess changes in vegetation cover within the communes of Madarounfa and Gabi. Table 2 summarises the evolution in surface area for each land cover class between 1987 and 2017. Woody vegetation formations, specifically savanna and gallery forest, exhibited significant regression over this 30-year interval. Table 2 Dynamics of land use units in Madarounfa and Gabi Table 3 provides an assessment of the quality of the land cover maps generated for the years 1987 and 2017, using three validation metrics: the Kappa coefficient, automated overall accuracy, and field-based (ground-truthed) overall accuracy. Table 3 Accuracy assessment of land use classification in Madarounfa and Gabi (1987 and 2017) 3.1. Land Use in 2017 Table 4 shows the various land cover areas across the two communes (Gabi and Madarounfa). Land cover units are divided into five classes (water bodies, gallery forests, savanna, steppe, and bare soil), with surface areas provided in both square meters and hectares. These data enabled us to calculate the extent of each land cover class in the communes of Madarounfa and Gabi for the year 2017. World Journal of Advanced Research and Reviews, 2025, 28(02), 251-259 255 Table 4 Land use surface areas in the two communes (Gabi and Madarounfa) in 2017 Visual interpretation and supervised classification of the 2017 Landsat 7 image enabled the mapping of land cover in our study area (Figure 3). The identified land cover classes include: Water body, Gallery forest, Steppe, Bare soil, Woody savanna, and Degraded forest. Figure 3 Land use classes in the communes of Madarounfa and Gabi in 2017. Figure 3 illustrates the spatial distribution and proportional coverage of land cover classes across the communes of Madarounfa and Gabi in 2017. Mosaics of savanna and associated steppe cover a combined area of 105,731.5 ha, predominantly located in the southern and central parts of the communes. Gallery forests, covering 129,304.8 ha, are primarily concentrated in the northeastern sector. World Journal of Advanced Research and Reviews, 2025, 28(02), 251-259 256 3.2. Land Cover in 1987 Table 5 presents the land cover areas for the two communes (Gabi and Madarounfa) in 1987. Land cover units are classified into five categories: water bodies, gallery forests, savanna, steppe, and bare soil. Surface areas are provided in both square meters and hectares, enabling the calculation of the extent of each land cover class within Madarounfa and Gabi communes for the year 1987. Table 5 Land use surface areas in the two communes (Gabi and Madarounfa) in 1987 Visual interpretation and supervised classification of the 1987 Landsat MSS image enabled the mapping of land cover in our study area. The identified land cover classes include: Water body, Gallery forest, Steppe, Bare soil, Woody savanna, and Degraded forest. Figure 4 Land use classes in the communes of Madarounfa and Gabi in 1987. Figure 4 presents the spatial distribution of land cover classes across the communes of Madarounfa and Gabi in 1987, each occupying distinct proportions of the total communal area. Mosaics of savanna and associated steppe, covering 40,959.36 ha, are predominantly located in the southern and central parts of the communes. Gallery forests, with an area of 14,292.05 ha, are primarily concentrated in the northeastern sector. World Journal of Advanced Research and Reviews, 2025, 28(02), 251-259 257 The results of this study on the communes of Madarounfa and Gabi reveal severe degradation of natural vegetation formations between 1987 and 2017, with a loss of 8,752 ha of savanna and 9,083 ha of gallery forest largely replaced by the expansion of bare soil, which now covers 57% of the total area. This trend aligns with broader patterns observed across Niger, where anthropogenic pressures, rapid population growth, and high demand for fuelwood are accelerating deforestation [2], [12], [1]. This trajectory reflects a regional phenomenon shared across West Africa. Similar dynamics have been documented in Burkina Faso [22], Benin [27], and Senegal [25], where mounting human pressures drive the large-scale conversion of natural ecosystems. At the continental scale, countries such as Ethiopia [30] and Nigeria face comparable levels of desertification. Globally, these findings resonate with the alarming trends highlighted in the Global Land Degradation Outlook [34], which estimates that one-third of the Earth’s land surface is now degraded. Despite varying local contexts, the combined effects of resource overexploitation and climatic variability, here evidenced by 17 rainfall-deficient years out of 32 [13], are undermining ecosystem resilience. This underscores the urgent need for integrated strategies encompassing sustainable land management, ecological restoration, and continuous remote sensing-based monitoring to reverse degradation trends. 4. Conclusion This study successfully characterised the dynamics of vegetation formations in the communes of Madarounfa and Gabi between 1987 and 2017, using remote sensing, field data, and geographic information systems (GIS). The methodological approach combined digital processing of Landsat imagery with ground-truth validation, enabling accurate discrimination of land cover classes. Mapping land cover changes over this 30-year period revealed significant landscape transformations. Notably, vegetation formations exhibited variable dynamics across thematic classes, reflecting the complex interplay of anthropogenic and climatic drivers. Compliance with ethical standards Disclosure of conflict of interest No conflict of interest to be disclosed. References [1] H. Abdourhamane, M. 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