Application of Satellite Imagery in the Differentiation of the Invasive Species of Nipa from Mangrove Vegetation

Abstract

Mangrove forests form one of the primary coastal ecosystems in the tropical and subtropical regions of the world with a high biodiversity value. Mangrove species are uniquely adapted to the Nigerian coasts, providing numerous biodiversity and ecosystem services and supporting coastal livelihoods within the Niger Delta. The gradual decline in the size of the Mangrove ecosystem, due to Nipa fruticans infestation, has spanned a period of over 40 years. So far, no quantitative estimate of loss of these Mangrove habitats has been carried out. This is as a result of the closeness in spectral characteristics between Nipa and different species of Mangrove and the difficulty of differentiating Nipa using earlier remote sensing products such as Landsat, JERS, Radarsat, SPOT and ERS. To address this gap, new satellite imagery was used to extract both textural and spectral information. This imagery, Pleiades and GeoEye-2, contained 16 high-resolution spectral bands that capture information in the visible and near-infrared (VNIR)for the first time. The study was validated with groundtruth surveys leading to the differentiation of Mangrove and Nipa in an area of interest measuring 162 sq. km along the Andoni River Estuary. From the results, major threats of Nipa to Biodiversity of the Mangrove were compiled. A ratio of 1:24 of Mangrove to Nipa within an area of over 16,200 hectares is indicative of a very high threat that can lead to extinction of Mangrove species. This TEXVEG tool’s capacity to determine loss of Mangrove species from Nipa infestation across the Niger Delta landscape will help environmental decision makers provide guidance for biodiversity conservation of Mangrove species. This technique has great potential for mitigating economic and environmental consequences for coastal communities, especially in areas with low Mangrove diversity and high Mangrove area and species loss.