Abstract
Burnt area mapping and fire frequency analysis were carried out in Hwange National Park, Zimbabwe. Hwange National Park typifies a savannah ecosystem which is semi-arid and fire-prone. This paper presents a geospatial analysis to quantify the spatial distribution and fire frequency from 2000 to 2006. Moderate Resolution Imaging Spectroradiometer (MODIS) images from 2000 to 2006 were obtained and classified for burnt area mapping. Linear pixel unmixing was used for image classification and subsequent mapping of burnt areas. The results showed that it was feasible to have discrimination of burnt areas and ‘un-burnt’ areas as well as generating a six year fire frequency map of the study area. Accuracy assessment of the classified images was carried out using field obtained information on fire occurrence to validate the classification results. An error matrix quantified accuracy of classified maps through producer's accuracy, user's accuracy and overall accuracy. High overall accuracy rates of appromately 96%, in turne, justify use of linear pixel unmixing in identifying and mapping burnt areas. Thus pixel unmixing offers a viable mapping tool for fire monitoring and management in protected areas.
Highlights
The increasing temperatures and decreasing precipitation, in Southern Africa’s savannah region, will continue to impact heavily on its fire regime (Kusangaya et al, 2013, Pricope and Binford, 2012). These changes will in turn affect the ecology, structure, and function of the savannah ecosystem
Fires on the African savannah burn large areas of vegetation annually (Dwyer et al, 2000) and this led to it being identified as one of the major threats causing the loss of forests in sub-Saharan Africa (Silva et al, 2003)
Image bands 1 (620-670 nm) and 2 (841-876 nm) of Moderate Resolution Imaging Spectroradiometer (MODIS) with a spatial resolution of 250m (NASA, 2013) were used. These image bands were selected because MODIS’s multi-spectral capabilities in the visible and near-infrared regions and narrow spectral bands have an advantage of improved spatial resolution compared to National Oceanic and Atmospheric Administration (NOAA)’s Advanced Very High Resolution Radiometer (AVHRR), previously widely used for burnt area mapping
Summary
The increasing temperatures and decreasing precipitation, in Southern Africa’s savannah region, will continue to impact heavily on its fire regime (Kusangaya et al, 2013, Pricope and Binford, 2012). These changes will in turn affect the ecology, structure, and function of the savannah ecosystem. Fires on the African savannah burn large areas of vegetation annually (Dwyer et al, 2000) and this led to it being identified as one of the major threats causing the loss of forests in sub-Saharan Africa (Silva et al, 2003). The fires, especially in the savannah biome, have led to Africa often being referred to as the “fire continent” (Navashni, 2003)
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