Spatiotemporal Dynamics and Burn Severity of Bushfires in the Gadabedji Biosphere Reserve (1993–2023)
Mai Adam Barma *
Faculty of Agricultural and Ecological Sciences, University of Diffa, Niger.
Salamatou Abdourahamane Illiasou
Faculty of Agricultural and Ecological Sciences, University of Diffa, Niger.
Diouf Abdoulaye
Faculty of Agronomy and Environmental Sciences, Dan Dicko Dankoulodo University of Maradi, Niger.
*Author to whom correspondence should be addressed.
Abstract
Bushfire is a fire that spreads over a minimum area of one hectare, affecting one or more vegetation types. In Niger, bushfires pose a serious threat to food security and biodiversity. The Gadabedji Biosphere Reserve, located north of the Maradi Region in the Sahelian savanna zone of central Niger, is particularly threatened, notably by late and uncontrolled fires. Each year, fires of varying intensity and extent destroy large areas of forest. New technologies such as remote sensing and geographic information systems play an important role in monitoring, assessing, and preventing forest fires. This study aimed to improve understanding of the severity of bushfires in the RBG (Réserve de Biosphère de Gadabedji) between 1993 and 2023 using satellite imagery and geographic information systems. More specifically, it analyses the spatiotemporal distribution of fires and burned areas within the RBG and identifies the main factors explaining this distribution. To achieve this, medium-resolution satellite data were used, namely Landsat-5 & 4 Thematic Mapper images, Landsat-7 Enhanced Thematic Mapper images, and Operational Land Imager images, corresponding to the periods before and after the fires. A marked periodicity of extreme fire years was observed, notably in 2003 and 2023; however, intensity remained low in 2013. The central zone is particularly vulnerable to fires and accounts for nearly 80% of the active fires detected across its entire area. The annual burned-area rate varies, depending on the scale, from 0.05% to 7.33% for the study area and from 0.01% to 40% within the central zone. The topomorphology of the study area influences the spread of bushfires: burned areas are primarily found at medium and high altitudes, on slopes, and in sectors with a high density of herbaceous cover. To mitigate their severity and impacts, appropriate risk-management plans should be developed and implemented before, during, and after bushfires. Monitoring and spatiotemporal analysis of fires at national, regional, and local levels are also essential for effectively organising early warning systems and improving fire prevention and management.
Keywords: Bushfire, burn severity, burned area, spatiotemporal dynamics, delta normalised burn ratio, normalised burn ratio, Landsat, remote sensing, GIS, Gadabedji Biosphere Reserve