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Modelling the economics of ecosystem services: nutrient retention in wetlands and fisheries in Lake Victoria

Fri, 01 Apr 2005 00:00:00 GMT

Title: Modelling the economics of ecosystem services: nutrient retention in wetlands and fisheries in Lake Victoria Authors: Perrings, C.; Simonit, S. Abstract: This paper models the effect of changes in wetlands yields within the freshwater fishery of (the Kenyan segment) of Lake Victoria. Specifically, it models the nutrient retention function of wetlands as a buffer against fertilizer run-off from agriculture, and the impact of nutrient loading on the fishery. Run-off from the watershed is among the major causes of eutrophication in the lake, along with atmospheric deposition and sewage and other organic discharges from domestic and industrial activities. The ecological component of the model captures the interactions between phosphorus loading, wetland area, water quality and fish stocks. Chlorophyll-a concentration is used as a proxy for phytoplankton density, and as a measure of nutrient enrichment. The impact of this on fish stocks is then estimated using using Ecopath. The economic component of the model then evaluates the effect of changes in stocks on performance in the fishery, given the regulatory regime in Kenya. We use the results to obtain an estimate of the value of the nutrient retention function of wetlands on the margins of the lake.

Biodiversity and Sustainable Management of a Tropical Wetland Lake Ecosystem: a case study of Lake Kanyaboli, Kenya

Sat, 01 Jan 2005 00:00:00 GMT

Title: Biodiversity and Sustainable Management of a Tropical Wetland Lake Ecosystem: a case study of Lake Kanyaboli, Kenya Authors: Abila, R. Abstract: Lake Kanyaboli and the surrounding Yala Swamp wetland have been recognized as an important biodiversity hotspot. Recent population, genetic and phylogenetic studies confirm the evolutionary importance of Lake Kanyaboli in preserving the cichlid fish fauna of Lake Victoria. The adjoining Yala Swamp harbours the endangered swamp antelope Sitatunga (Tragecephalus spekii) and several papyrus endemic birds. The lake and adjoining swamp play a critical role in the livelihood of the local communities who heavily depend on the wetland resources. Current ongoing large scale land use and changes within the swamp threaten the ecological integrity and functioning of this highly dynamic wetland ecosystem. It is therefore imperative that proper management and conservation measures are put in place to protect Lake Kanyaboli and the associated Yala Swamp. This paper presents a review of the biodiversity of Lake Kanyaboli and the associated wetland and the threats this ecosystem has to face. Polycultural finger-ponds aquaculture (see Figure 3), tourism and papyrus based industries as well as an all-stakeholders-driven management plan are suggested as a step towards achieving sustainable management, utilization and conservation of the Lake Kanyaboli ecosystem.

Participatory habitat characterization and GIS data base development for the conservation and management of Sea Turtles in South Coast Kenya

Sat, 01 Jan 2005 00:00:00 GMT

Title: Participatory habitat characterization and GIS data base development for the conservation and management of Sea Turtles in South Coast Kenya Authors: Muasa, J.; Nzuki, S. Abstract: Three sites in south coast Kenya i.e. Msambweni, Funzi and Bodo were studied with an overall objective of characterizing the existing sea turtle nesting and foraging habitats. Nesting beach stretches in Msambweni and Funzi were evaluated based on human and natural predation indices and environmental factors which considered temperature measurements. The targeted foraging grounds consisted of seagrass beds and associated food items which included sponges and mollusks. Participatory approaches as well a stratified sampling design were used in studying both habitats. A total of 10 beach stretches measuring 5.84km were identified in both Funzi and Msambweni. Msambweni beaches had a higher index of human pressure than Funzi beaches although the later had a higher natural predation index in relation to clutch and nesting females’ survival. The mean temperature range at a depth of 10-30cm was higher for the Funzi hatchery when compared with samples from Funzi beaches (t= 2.7, p<0.05) but was not significant when compared with measurements from Bodo beach stretches (t= 0.05, p>0.05). However there were significant differences in temperature range reported within sites i.e. Funzi (t= 1.73, p< 0.05) and Msambweni beaches (t= 4.00, p<0.05) at depths of 10-30cm. Funzi had the highest mean temperature range at all depth measurements. Seagrass cover ranged from 1.3-44.23% but there was no significant differences (p>0.5) between sites. Most of the sampling stations were dominated by Thelassodendron ciliatum, Thalassia hemprichii, Siringodium isoetifolium, and Halodule uninervis. A two-factor ranking exercise identified fisheries, sea urchins and pollution as the most immediate threats to sea turtle habitats within the study sites. The overall mean densities of sponges were higher in Msambweni than in Funzi - Bodo sites pooled (p<0.001) while there were more mollusks within the Funzi-Bodo channels compared to Msambweni (p<0.001). The distribution of gelatins was not significant between the two sites (p>0.05). Interviews with fishermen and observations suggest a spatial coincidence between specific seagrass pastures and green turtle sightings. During the survey period 67 green turtle nests were sighted in Funzi and Msambweni beaches and a total of 32 mortality cases reported.

Kenyan Exports of Nile Perch: impact of food safety standards on an export-oriented supply chain

Tue, 01 Jun 2004 00:00:00 GMT

Title: Kenyan Exports of Nile Perch: impact of food safety standards on an export-oriented supply chain Authors: Mitullah, W.; Henson, S. Abstract: Over the past decade, exports of fish and fishery products from developing countries have increased rapidly. However, one of the major challenges facing developing countries in seeking to maintain and expand their share of global markets is stricter food safety requirements in industrial countries. Kenyan exports of Nile perch to the European Union provide a notable example of efforts to comply with such requirements, overlaid with the necessity to overcome restrictions on trade relating to immediate food safety concerns. Although food safety requirements were evolving in their major markets, most notably the EU, most Kenyan exporters had made little attempt to upgrade their hygiene standards. Likewise, the legislative framework of food safety controls and facilities at landing sites remained largely unchanged. Both exporters and the Kenyan government were forced to take action when a series of restrictions were applied to exports by the EU over the period 1997 to 2000. Processors responded by upgrading their hygiene controls, although a number of facilities closed, reflecting significant costs of compliance within the context of excess capacity in the sector. Remaining facilities upgraded their hygiene controls and made efforts to diversify their export base away from the EU. Legislation and control mechanisms were also enhanced. Hygiene facilities at landing beaches were improved, but remain the major area of weakness. The Kenyan case illustrates the significant impact that stricter food safety requirements can have on export-oriented supply chains. It also demonstrates how such requirements can exacerbate existing pressures for restructuring and reform, while prevailing supply and capacity issues constrain the manner in which the supply chain is able to respond. In Kenya most of the concerted effort to comply with these requirements was stimulated by the sudden loss of market access in very much a “crisis management” mode of operation, illustrating the importance of responding to emerging food safety requirements in a proactive and effective manner. This paper - a product of the International Trade Department, Poverty Reduction and Economic Management Network - is part of a larger effort in the network to understand the challenges and opportunities facing developing countries associated with evolving international standards for food and other products.