Advances in satellite remote sensing of the wetland ecosystems in Sub-Saharan Africa

Abstract

Wetlands are highly productive systems that act as habitats for a variety of fauna and flora. Despite their ecohydrological significance, wetland ecosystems are severely under threat from global environmental changes as well as pressure from anthropogenic activities. Such changes results in severe disturbances of plant species composition, spatial distribution, productivity, diversity, and their ability to offer critical ecosystem goods and services . However, wetland degradation varies considerably from place to place with severe degradation in developing countries, especially in sub-Saharan Africa due to poor management practices that leads to underutilization and over reliance on them for livelihoods. The lack of monitoring and assessment in this region has therefore led to the lack of consolidated detailed understanding on the rate of wetland loss. For example, the lack of up-to-date and reliable spatial explicit information further complicates the management of wetland ecosystems in semi-arid tropical environments. To monitor, understand and document wetland degradation rate, the use of remote sensing for accurate estimation and precise mapping of present and historic information remains imperative. Similarly, there is a need to develop robust methodologies to precisely assess and monitor wetland degradation, ecohydrological processes and wetland condition over space and time. This work thereof, provides a comprehensive overview of remote sensing applications in monitoring and mapping the wetland ecosystem. It also highlights the strength and challenges associated with the use of satellite data for purposes of wetland monitoring. Spatial explicit and periodic information offered by satellite remote sensing demonstrate a unique opportunity for documenting and understanding of wetlands, their ecohydrological processes, and environmental conditions.

Leveraging Google Earth Engine platform to characterize and map small seasonal wetlands in the semi-arid environments of South Africa

“…Accurate detection and monitoring of small seasonal and heterogeneous wetlands in the semi-arid regions is important for understanding the ecohydrological dynamics of these systems, as most of these wetlands particularly in the sub-Saharan Africa offer socio-economic benefits to the surrounding communities (Gardner et al, 2009;Kabii and Kabii, 2005;Thamaga et al, 2021). Advancements in data analytic tools provide unique opportunities to improve the detection and monitoring of semi-arid wetlands of variable sizes, which were not feasible, using the traditional remote sensing techniques.…”

Progress in the remote sensing of groundwater-dependent ecosystems in semi-arid environments

“…The GDEs aspects were studied successfully due to the capabilities and technological advancement of satellite datasets. For instance, Sentinel with finer spatial (10 m) and higher spectral (13 spectral bands including red edge strategic bands) resolution with varying geographical coverage up to (290 km), which is essential for extraction of GDEs such as wetland ecosystem characteristics and for the evaluation of wetland dynamics (Thamaga et al, 2021).…”

“…However, passive satellite sensors such as Landsat, Sentinel, MODIS, and SPOT with medium to coarse resolution multispectral data have also been used to map GDEs mostly due to their zero to low cost and spatial extent covered by satellite imagery (Pérez Hoyos et al, 2016). Advances in Sentinel datasets with fine spatial resolution (10 m) offers an opportunity for extraction of GDEs characteristics and status (Thamaga et al, 2021).…”

Evaluating the impact of land use and land cover change on unprotected wetland ecosystems in the arid-tropical areas of South Africa using the Landsat dataset and support vector machine

“…Although wetlands occupy approximately 6% of the earth's surface, they are among the most productive and ecologically diverse ecosystems globally. In their natural condition, wetlands support many environmental and socio-economic services to the neighbouring communities, which are, to some extent, largely controlled by the variations in inundation and soil saturation patterns (Dubeau et al 2017;Thamaga et al 2021). These ecosystems play a critical role by controlling floods, moderating micro-climates, maintaining and improving the water quality and protecting against erosion (Calhoun et al 2017;Chandler et al 2017;Materu et al 2018).…”