Buffering Capacity Studies in a Rural and Urban Wetlands in Lake Victoria Catchment in Uganda

Wetlands are known to filter water from catchments by retaining solid waste, and eroded sediments from catchment areas. Wetlands also reduce the impact of flooding, speed of flow, and hence store water while releasing it slowly. The extent to which the wetlands perform these roles was investigated in two wetlands, Kinawataka wetland with an industrial and heavily populated catchment, and Kisoma wetland with subsistence agricultural catchment between January 1999 to July 2001. Water samples were collected once a month from streams entering the wetlands, along transects within the wetland and at the out flow. Parameters investigated included pH, temperature, dissolved oxygen (DO), electric conductivity (EC), Total Dissolved Solids (TDS), orthophosphates, Total Phosphorus (TP), nitrates, Total Nitrogen (TN) and chemical oxygen demand (COD). Results showed that the urban Kinawataka wetland receives a lot of pollution from its catchment and this is considerably reduced as the water move through it to the out flow. Reductions of TN by 50% and TP by only 10% were noted. The rural Kisoma wetland however receives fewer nutrients from its catchment but releases more in its out flow. There were increases in orthophosphates to about 50%, TP to 40% and nitrates to 22%. In situations where large volumes of water was received especially after a heavy storm or during floods, the wetland capacity to buffer was impaired and the materials from the catchment would pass through it unbuffered. It is suggested that wetland buffering depends on the amount of nutrients and water inflow from the catchment, the wetland-slope, nature of the vegetation, size of the wetland, catchment rainfall and anthropogenic characteristics. The conditions within the wetlands modify the nature of the nutrients as the water flow through them.Key words: Buffering capacity, wetland buffering, catchment, reservoir, nutrient

Effectiveness of a biological control agent Palexorista gilvoides in controlling Gonometa podorcarpi in conifer plantations of Uganda

Widespread defoliation of plantation forests by insect pests causes economic losses worldwide. Successful pest outbreak management requires knowledge of effective pest management options. Currently, such knowledge is inadequate for Gonometa podocarpi an indigenous pest that has devastated conifer plantations in Uganda since the 1960s. The pest is a serious defoliator of conifers in East Africa and was first described from Mt. Elgon Kenya, where its larvae were defoliating indigenous conifer; Podocarpus spp. The pest has since adapted to feeding on exotic conifers. There have been several serious resurgences of this pest in Uganda, the latest being 2011 and 2012. Studies carried out during the peak of these outbreaks in Muko, Kiriima and Mafuga Central Forest reserves in South Western Uganda established G.podocarpi infestations in Kiriima and Mafuga but none in Muko. The studies also identified a tachnid fly, Palexorista gilvoides as a potential biological control agent for G. podocarpi. Field and laboratory studies further established that P. gilvoides is a larval parasitoid of G.podocarpi, with parasitism levels of 43.0 and 62.0% in the field and laboratory respectively. These levels of parasitism are considered high enough to control the pest. However, causes of this pest resurgence need further investigations.Keywords: Defoliator, parasitoid, parasitism, pest outbreak, resurgenc

Wetland Cultivation and Hydrological Management in Eastern Africa: Matching Community and Hydrological Needs Through Sustainable Wetland Use.

Wetlands are critical natural resources in developing countries where they perform a range of environmental functions and provide numerous socio-economic benefits to local communities and a wider population. In recent years, however, many wetlands throughout eastern Africa have come under extreme pressure as government policies, socio-economic change and population pressure have stimulated a need for more agriculturally productive land. Although wetland drainage and cultivation can make a key contribution to food and livelihood security in the short term, in the long term there are concerns over the sustainability of this utilization and the maintenance of wetland benefits. This article draws upon recent research carried out in western Ethiopia, which addressed the sustainability of wetland agriculture in an area of increasing food insecurity and population pressure. It discusses the impacts of drainage and cultivation on wetland hydrology and draws attention to local wetland management strategies, particularly those characterized by multiple use of wetlands, where agriculture exists alongside other wetland uses. The article suggests that where multiple wetland uses exist, a range of benefits can be sustained with little evidence of environmental degradation. Ways of promoting and empowering such sustainable wetland management systems are discussed in the context of the wider need for water security throughout the region