Spatiotemporal analysis of encroachment on wetlands: a case of Nakivubo wetland in Kampala, Uganda

Abstract

Wetlands provide vital ecosystem services such as water purification, flood control, and climate moderation among others, which enhance environmental quality, promote public health, and contribute to risk reduction. The biggest threat to wetlands is posed by human activities which transform wetlands, often for short-term consumptive benefits. This paper aimed to classify and map recent land cover and provide a multi-temporal analysis of changes from 2002 to 2014 in the Nakivubo wetland through which wastewater from Kampala city drains to Lake Victoria in Uganda. The paper contributes through spatially congruent change maps showing site-specific land cover conversions. In addition, it gives insight into what happened to the wetlands, why it happened, how the changes in the wetlands affect the communities living in them, and how the situation could be better managed or regulated in future. The analysis is based on very high resolution (50-62 cm) aerial photos and satellite imagery, focus group discussions, and key informant interviews. Overall, the analysis of losses and gains showed a 62 % loss of wetland vegetation between 2002 and 2014, mostly attributable to crop cultivation. Cultivation in the wetland buffering the lake shore makes it unstable to anchor. The 2014 data shows large portions of the wetland calved away by receding lake waves. With barely no wetland vegetation buffer around the lake, the heavily polluted wastewater streams will lower the quality of lake water. Furthermore, with increased human activities in the wetland, exposure to flooding and pollution will be likely to have a greater impact on the health and livelihoods of vulnerable communities. This calls for a multi-faceted approach, coordination of the various stakeholders and engagement of wetland-dependent communities as part of the solution, and might require zoning out the wetland and restricting certain activities to specific zones.

Socio-Economic Determinants of Land Use/Cover Change in Wetlands in East Africa: A Case Study Analysis of the Anyiko Wetland, Kenya

“…The reduction in size of the Anyiko wetland was, however, not only because of farmland expansion, but also encroachment of open and close shrublands by 15 and 2%, respectively. This finding is consistent with the study of Isunju and Kemp (2016), which reported a loss of Nakivubo wetland in Uganda by 2% between 2002 and 2014 because of encroachment by trees and shrubs (shrubland). Typically, wetlands are inhabited by flood tolerant vegetation (Cronk and Fennessy, 2016) and therefore encroachment by shrubland indicate drying out of some parts of the wetland.…”

“…Loss of wetlands to agriculture in sub-Saharan Africa have also been reported by other studies. For example, Isunju and Kemp (2016) reported 62% of the wetland vegetation loss in Nakivubo wetland in Uganda, between 2002 and 2014, 30% of which was due to drainage and conversions to farmland. In addition, Troy et al (2007) reported 52% loss of Ga-Mampa wetland in South Africa between 1996 and 2004 to farmland.…”

“…Jogo and Hassan (2010), however, argue that although there is increased awareness on the values of wetlands, degradation and land use change continue to occur. This is evident in several case studies in East Africa such as Nakivubo wetland in Uganda (Emerton et al, 1999;Kansiime and Nalubega, 1999;Isunju and Kemp, 2016), Nyando and Yala wetlands in Kenya (Schuijt, 2002;Kipkemboi et al, 2007;Onywere et al, 2011;Khisa et al, 2013;Oduor et al, 2015). The conversion to agriculture is not only initiated by the local people, but also by governmental programmes (Swallow et al, 2007;Nabahungu and Visser, 2011).…”

“…Studies explicitly quantifying spatio-temporal extents of wetlands encroachment by human activities in sub-Saharan Africa are limited (Mwita et al, 2013;Isunju and Kemp, 2016). Understanding the linkages between wetlands conversion to agriculture and socio-economic determinants including households' perceptions on their values is important.…”

A review of the socioecological causes and consequences of cyanobacterial blooms in Lake Victoria

“…In the Kampala Metropolitan Area (Uganda), the proportion of severely degraded wetlands increased from 13% in 1993 to 46% by 1999 (Nyakaana et al, 2007). In particular, Nakivubo wetlands experienced a 62% loss in wetland vegetation between 2002 and 2014, mainly due to crop cultivation (Isunju, 2016), despite their high estimated economic value of between US$ 760,000-1,300,000 (Schuijt, 2002). Similar observations have been made for the Nyanza Gulf in Kenya by Juma et al (2014).…”