Detecting level of wetland encroachment for urban agriculture in Uganda using hyper-temporal remote sensing

DOI

Urbanization is an important indicator of economic growth and social change but is associated with environmental degradation, which threatens sustainable growth of African cities. One of the most vulnerable ecosystems in urban areas are wetlands. In Uganda, wetlands cover an area of 11% of the country's land area. Half of the wetland areas in Ugandan cities have been converted to industry and residential areas, and urban agriculture. There is limited information on the extent of wetland conversion or utilization for urban agriculture. The objective of this study was to investigate the extent of wetlands lost in two Ugandan cities, Wakiso and Kampala, in the last 30 years. Secondly, we demonstrate a simple methodology to monitor agriculture on encroached wetlands.Methods: Using a field survey and free remote sensing data from Landsat TM 1986 and Landsat ETM 2016 we classified the rate of wetland loss and encroachment in the last 30 years. Using MODIS NDVI 16-day composites at 500-meter spatial resolution, we generated distinctive crops and crop mixtures in the encroached wetlands for urban agriculture using the ISODATA clustering algorithm.Results: Over a 30-year period, 72,828 ha (73%) of the Wakiso-Kampala wetlands have been lost. Agriculture area on the other hand doubled. Of the new cultivation area, 16,488 ha (23%) were reclaimed from wetlands. All cultivated agriculture in Kampala was in the wetlands while in Wakiso, 73% of crop agriculture was in the wetlands. The major crops grown in these urban wetlands were banana (20%), sugarcane (22%), maize (17%), Eucalyptus trees (12%), sweet potatoes (10%), while ornamental nurseries, pine trees, vegetables and passion fruits were each at 5%.Conclusions: The Kampala-Wakiso wetlands have been disappearing at a rate of 2500 ha annually for the last 30 years, implying that at this rate, there will be no wetlands left by 2029. Policy implications are that, ecosystem services by of urban wetlands have been lost, a large population of urban poor are using wetlands for survival and yet Poverty eradication policies are in conflict with wetland conservation policies. Policy recommendations we endorse are,the Government of Uganda needs to promote wetland reclamation programs so as to restore and reconstruct lost and fragmented wetlands. Secondly, ministries mandated to food security and poverty eradication need to convene with ministries regulating wetlands to merge these conflicting policies. Thirdly, there is need for the development of polices that are inclusive of challenges faced by the urban poor while at the same time minimize the pressures on urban environments.

Identifier
DOI https://doi.org/10.1594/PANGAEA.915587
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.915587
Provenance
Creator Kabiri, Stella; Allen, Molly; Okuonzia, Judith Toma; Akello, Beatrice; Ssabaganzi, Rebecca; Mubiru, Drake
Publisher PANGAEA
Publication Year 2020
Rights Creative Commons Attribution 4.0 International; https://creativecommons.org/licenses/by/4.0/
OpenAccess true
Representation
Resource Type Dataset
Format application/zip
Size 676.1 kBytes
Discipline Earth System Research
Spatial Coverage (31.883 LON, 1.067 LAT); Africa, Uganda