Tana River Delta Research Articles

Fishery Characteristics and Management in the Floodplain Lakes of Tana River delta, Kenya

Tana River delta floodplain is maintained through a dynamic balance revolving around frequency, extent, and flooding duration. These seasonal and annual flooding variations strongly affect the floodplain communities' fisheries and livelihoods. In the delta, fishing is an important traditional source of livelihood, practiced alongside local agrarian livelihoods such as shifting cultivation and livestock keeping. Fishery utilization and management characteristics in the Tana River delta floodplain lakes are not well documented. This study investigated the characteristics and management of small-scale fisheries in the Tana River delta floodplain lakes. Information relating to past flooding events, fishery characteristics, prevailing regulatory regimes, and the impacts of seasonal flooding were collected using field observations. We collected the information at awareness workshops and key informant interviews between June and September 2018, which covers a significant flooding period of that year, and August 2021, a relatively dry period in the delta. We collected the information from communities living around floodplain lakes in Tarassa and Ngao in the southern part of the delta and Tamaso and Lango la Simba areas in the eastern part of the delta. Results indicate that fishery resources are more diverse during flooding (new species recruitment, presence of spawning, breeding, and foraging sites). The community does fishing all year round, and some part-time practice fishing to supplement shifting cultivation and dry season grazing that are greatly affected by periodic flooding. Floods were crucial in enriching floodplain lakes with diverse fish species. Women are involved in fish trading, acquiring fish primarily within their lineage. Fish is mainly sold in local markets due to poor preservation leading to low-value addition. This study recommends a comprehensive value chain analysis to improve it. Fishing communities around the villages are also most vulnerable to climate change because fishery resource governance needs strengthening, and most households are not involved in resource management. Besides, fishers have limited livelihood options due to lacking skills, technologies, and knowledge to undertake climate adaptation-related decisions. We recommend desilting floodplain lakes and improving connectivity with the main river channel. Additionally, an urgent need is to institute a co-management system to bring together different user groups around these floodplain lakes. Keywords: Fisheries, Flooding, Livelihoods, Floodplain lakes, Governance, Tana River delta DOI: 10.7176/JEES/13-2-02 Publication date: March 31 st 2023

Evaluating the combined impacts of hydrological change, coastal dynamics and human activity on mangrove cover and health in the Tana River delta, Kenya

The long-term dynamics of tropical mangrove ecosystems, and especially how they have responded to the combined pressures of local human activity, changing river hydrology and climate-change related coastal processes are insufficiently documented. In this study we combined a chronological sequence of remote sensing data spanning the last three decades (1992–2021) with time series of river-flow and precipitation data to discriminate between the respective impacts of hydroclimatic drivers and land-use changes on mangroves of the Tana River delta in Kenya. Our land-cover analysis showed an overall increase in mangrove forest cover of 5.5% over the past 30 years, however this included a 14% increase between 1992 and 2013 followed by a 8% decrease between 2013 and 2021. Normalised Difference Vegetation Index (NDVI) data still indicate an overall positive trend (R2=0.58, p< 0.01) in the overall health of Tana River delta mangroves between 1992 and 2021. We also observe positive correlations between mangrove NDVI and precipitation (R=0.41, p=0.042) and Tana River water level (R=0.82, p< 0.0001), as well as between mangrove NDVI and modelled measures of Tana River discharge (R= 0.79, p< 0.0001) and flooded area (R=0.73, p< 0.001). Overall our results show that recent historical variation in the areal cover and health of Tana River mangroves is mainly associated with changing hydrology in the Tana River delta, but that intensifying local land use and accelerating coastal erosion has also impacted their health. We suggest that management of the Tana River delta mangroves should focus on improving Tana River flows and sediment recharge.

Becoming flood insecure: Lessons from village level experiences in Tana Delta, Kenya

Floods affect the human security conditions of floodplain residents. The aim of this paper is to explore how residents of the Tana River Delta in Kenya become flood insecure. This paper utilises assemblage theory, particularly the principles of rhizomatic multiplicity to explain the concept of becoming flood insecure. It combines these rhizomatic multiplicity principles with disruptions to the pillars of human security which are becoming afraid, becoming wanting and becoming undignified and their composite conditions of human insecurity to create an analytical framework with which to understand becoming flood insecure. The study sources its data from Focus Group Discussions in 10 sampled villages in the Tana River Delta. The results reveal that becoming flood insecure is a rhizomatic multiplicity and that the pillars and conditions of human security that comprise it are heterogenous and interconnected. The results reveal the conditions of human insecurity in the Tana River Delta as personal, food, water, fuel, housing, health, environment, and political. They also reveal that while children become more flood insecure, they are also the most adaptive. Additionally, the results show that there are transitory conditions of human insecurity, food, housing health, to which people attempt to find local solutions and redundant conditions of human insecurity, political, health, water, personal and environment, to which people cannot find local solutions and public action is required.

Geomorphic and Climatic Drivers Are Key Determinants of Structural Variability of Mangrove Forests along the Kenyan Coast

Mangrove forests occur across a diversity of coastal landforms that influence their structural development and productivity. Preliminary studies in Kenya indicate that mangroves growing in the region north and south of Tana River delta have different structural attributes. We hypothesise a close relationship between mangrove distribution, climate and landform types. Floristic composition of mangroves along the coast of Kenya was characterised and differences illustrated using non-metric multidimensional scaling (nMDS). Other structural properties of mangroves such as tree height, basal area, stand density and standing biomass were also assessed and their differences tested using analysis of variance (ANOVA). A hierarchical cluster analysis was used to compare mangrove species based on structural properties. Additionally, a regression fit model was used to investigate the relationship between mangrove standing biomass and possible drivers of variability. The study revealed significant differences in mangrove tree diameter, tree height, basal area, stand density and standing biomass across the sampled sites. High values of structural complexity were observed in estuarine and deltaic settings with high influence of freshwater input whereas low levels of structural complexity were observed for peri-urban with direct human influence. Our findings suggest that structural variability of mangroves in Kenya is highly influenced by geomorphological and climatic variability along the coast as well as the past and present management regimes of the forest.

Natural resource-use in the Lower Tana River Delta based on household surveys and remote sensing of land cover and land use patterns

Household survey data and spatially explicit Sentinel-2 satellite images of land cover and land use during the dry and wet seasons were used to investigate livelihood strategies in the Lower Tana River Delta in Kenya, where food security and economic activity rely almost exclusively on ecosystem goods and services. Land cover classification of satellite imagery successfully showed seasonal changes to estuary-related vegetation and habitats from which land use cycles could be inferred. Flood-recession agriculture and part-time fishing were the most common activities at Ozi village, some 10 km upstream from the estuary mouth, whereas full-time fishing dominated activities at Kipini town, where the Tana Estuary discharges into Ungwana Bay. Seasonality of fishing at Kipini depended on favourable sea conditions, arrival of migrant fishers and peaks in shrimp abundance. Seasonality of agriculture at Ozi depended on the freshwater flooding regime, visible in satellite images as an inverse relationship of areas covered by wetlands and cultivated lands. The predominance of fishing assets at Kipini indicated specialization, which underlies a socio-economic network of fish processing, marketing, distribution and logistical support services. In contrast, mixed farming assets and traditional fishing gear at Ozi reflected more diversified farmer-fisher livelihoods, as a risk avoidance strategy. Key outcomes of this study were that land cover and land use were strongly seasonal, that coastal and upstream communities in the Tana Estuary relied on different combinations of ecosystem goods and services, and that livelihood strategies at the two locations differed fundamentally. Combining social, spatial and ecological data to describe socio-ecological systems typical of the Tana Estuary provided a broad platform for shared resource management strategies.

Optimization of a Loop-Mediated Isothermal Amplification Assay as a Point-of-Care Tool for the Detection of Wuchereria bancrofti in Human Blood in Tana River Delta, Kenya.

Introduction Accurate detection of filarial parasites in humans and vectors is essential for the implementation and evaluation of Global and National Programs to eliminate lymphatic filariasis. Immunological methods to detect infection are available; however, cross-reactivity issues have been reported in most of them. Nucleic acid-based molecular assays offer high levels of specificity and sensitivity and can be used to detect the infections. Methods In this study, we evaluated loop-mediated isothermal amplification (LAMP) tests to amplify Wuchereria bancrofti DNA in patients' blood. The amplicons were tested by both pH-sensitive dyes for enhanced visual detection and agarose gel electrophoresis. A closed-tube LAMP assay was also evaluated. Cohen's Kappa statistics was used for statistical analysis of the assays. 125 patients consented for blood sampling which were used for clinical analysis of LAMP assays with the PCR method used as the “gold standard.” Results The sensitivity of the evaluated Wuchereria bancrofti LAMP was 92.3%, with a specificity of 97.3% and kappa statistics value of 0.84, which is in a strong agreement. Conclusion In this study, LAMP assays coupled with fluorescence dye detection have been found to be suitable for diagnosis and monitoring of Wuchereria bancrofti infections in the Kenyan population.

Monochoria africana N.E.Br. [Family Pontederiaceae]: Probable Reasons for Limited Distribution of This Rare Species in Kenya

Monochoria africana N.E.Br. is an extremely rare plant with limited distribution in Kenya. Rare plant species are often specialists for a rare microhabitat and there is all likelihood that Monochoria africana is a habitat specialist. Our research on distribution of this species in Kenya has so far located it in a very small isolated microhabitat in the Tana River delta, coastal region of Kenya. So far, this plant has only been located in one community farm in a small village called Ozi, near Kipini, Latitude 2°30’33’’S and Longitude 40°27’20’’E. The methodology used in this study entailed direct observations, line transects, meander and patterned searches in its narrow area of endemism.&#x0D; In this short communication, the authors hypothesize various reasons for the limited distribution of this rare species. Viz: diverse edaphic factors, inbreeding depression, low levels of seed set, genetic bottlenecks, specialized pollination systems etc. At the Jomo Kenyatta University of Agriculture and Technology (JKUAT) department of Botany greenhouses, we have embarked on some studies to try and unravel probable reasons for rarity of Monochoria africana.

Yearning for an Apple: The Changing Lifestyle of the Tana River Delta Communities in Kenya and Implications on Livelihoods and Conservation of Natural Resources

Tana River Delta is occupied predominantly by pastoral and farming communities that inhabit defined zones in the Delta. A study was undertaken to assess changes in the lifestyle of communities living in the Delta and its implications on livelihoods and conservation of natural resources. Literature review, household questionnaires, social and resource mapping, key informant interviews, village-based focus group discussion and structured observations were used to collect data. It was evident that the delta communities are aware of the delta resources, their uses, utilization and best management options. Additionally, they were knowledgeable on the delta resources use by non-residents, the resultant conflicts and the food status in the community. They had a good understanding of the new food they would wish to have in their diets and the means of accessing them. Modernity has pushed the community to yearn for development (“Yearn for an Apple”) to access foods that other parts of the country are eating, with implications on livelihoods and conservation of Delta resources. Reversing degradation and enhancing the development of the Delta area require the involvement of all stakeholders, informing and seeking the consensus of decision-makers and the real users of the Tana delta. The Government has to provide overall security and development.

Influence of Floods and Growth Duration on the Productivity of Wet Grasslands of Echinochloa stagnina (Retz) P. Beauv. in an East African Floodplain

Echinochloa stagnina (Retz) P. Beauv., a widespread semi-aquatic perennial grass, is a key species for the sustainability of many African wetlands. In an effort to assess interactions between hydrological regimes and management strategies targeting conservation, this study focuses on characterizing the growth of a typical East African wet grassland and describing the relative influence of floods and management practices on its growth rates. Naturally flooded grassland, subjected to a factorial design protocol with different levels of irrigation and cutting frequencies, was sampled during 15 months in the Tana River Delta, Kenya. Statistical analyses of the data, using linear mixed models accounting for temporal auto-correlation, were undertaken. Reduced cutting frequencies slightly increased growth rates, except under water-limited conditions. Increased water supply had a positive effect on growth rates, the latter noting a five- and ten-fold increase from water-limited to water non-limited to flooded conditions. Floods impacted grasslands by increasing growth rates, which attained very high values of 225 kgDM ha−1 day−1, extending growth period and limiting the negative effect of severe phytomass removal through clipping. These results support the view that rangeland and water management for the Tana River Delta, and more widely for tropical floodplain grasslands, should be jointly undertaken.

Modelling the growth of floodplain grasslands to explore the impact of changing hydrological conditions on vegetation productivity

This study (i) presents a coupled vegetation-soil model adapted to perennial C4 seasonally flooded semi-arid grasslands; and (ii) applies the model to evaluate changes in the annual productivity of the grasslands of the Tana River Delta, Kenya, under changing flooding conditions. Main plant growth processes are modelled within coupled plant carbon balance and soil water budget modules: photosynthesis, allocation of photosynthates, respiration, translocation of root phytomass to aerial phytomass, senescence and litter production. Aerial phytomass can also be subtracted from the system, to simulate grazing or cutting. New features concern the inclusion of effects of floods on energy conversion efficiency, photosynthate allocation, senescence and litter production. The vegetation model, composed of four phytomass compartments (leaves, stems, roots, aerial dead matter), simulates three main growth phases related to flooding: floods, a post-flood phase and a non-flooded phase. It was designed to be used with limited climatic data. Data collected during a 14-month experiment (2010–2012) in the Tana River Delta, Kenya, in which different irrigation and cutting treatments and flood events were recorded, were used for calibration and validation purposes. Fourteen parameters, selected through a sensitivity analysis, were calibrated on half of these treatments. Uncertainty in parameter estimation was expressed through a stochastic ensemble of simulations. The remaining independent data were used for model validation. Overall, the model predictions are in good agreement with the experimental data. This model can be used to assess the impact of rain variability, grazing or flooding patterns on the annual primary productivity of Sub-Saharan floodplain grasslands composed mainly of Echinochloa stagnina (Retz) P. Beauv. In particular, simulations for the Tana River Delta suggest that past changes in the hydrological regime of the river, as well as future changes due to the construction of hydroelectric infrastructure, have led and will certainly lead to an important decrease of the floodplain grassland productivity. As local and regional livestock keeping activities rely heavily on the dry seasons’ grazing resources available within the wetland, future development plans should seriously consider the negative effects of these changes on local activities and livelihoods.

Carbon stocks of the terraces of the Lower Tana River floodplain and delta, Kenya, prior to conversion for biofuel production

Few studies have addressed the terraces adjacent to the Tana River and delta. In May 2012 a survey assessed the woody vegetation of the terraces in anticipation of their conversion to a biofuel farm. The 64 000 hectares targeted by Bedford Biofuels for clearing for Jatropha curcas would have released over 1 million Mg of carbon at a social cost of the order of US$36 million. The lease agreement set the payment to the communities at US$0.75 per hectare per year, i.e. about US$100 000 annually. The intact terraces are a resource for famine food, fodder, traditional medicine for humans and livestock, firewood, fencing and housing, but are especially important for pastoralist communities at the beginning of the dry season when waiting for the deltaic floodplain pastures to become accessible. They are also important migratory routes for wildlife, including elephants, dispersing to and from the Tsavo ecosystem. It is unlikely that the communities would have derived substantial benefits from conversion. Maintaining and even improving the carbon storage on these semi-arid lands would therefore be a better option, especially if compensation was available through the Reducing Emissions from Deforestation and Forest Degradation (REDD+) programme. The biofuel company has since abandoned the project.

Schistosoma haematobium and soil-transmitted Helminths in Tana Delta District of Kenya: infection and morbidity patterns in primary schoolchildren from two isolated villages.

BackgroundSchistosomes and soil-transmitted helminths (STH) (hookworm, Trichuris trichiura and Ascaris lumbricoides) are widely distributed in developing countries where they infect over 230 million and 1.5 billion people, respectively. The parasites are frequently co-endemic and many individuals are co-infected with two or more of the species, but information on how the parasites interact in co-infected individuals is scarce. The present study assessed Schistosoma haematobium and STH infection and morbidity patterns among school children in a hyper-endemic focus in the Tana River delta of coastal Kenya.MethodsTwo hundred and sixty-two children aged 5–12 years from two primary schools were enrolled in the study. For each child, urine was examined for S. haematobium eggs and haematuria, stool was examined for STH eggs, peripheral blood was examined for eosinophilia and haemoglobin level, the urinary tract was ultrasound-examined for S. haematobium-related pathology, and the height and weight was measured and used to calculate the body mass index (BMI).ResultsPrevalences of S. haematobium, hookworm, T. trichiura and A. lumbricoides infection were 94, 81, 88 and 46 %, respectively. There was no significant association between S. haematobium and STH infection but intensity of hookworm infection significantly increased with that of T. trichiura. Lower BMI scores were associated with high intensity of S. haematobium (difference =−0.48, p > 0.05) and A. lumbricoides (difference =−0.67, p < 0.05). Haematuria (both macro and micro) was common and associated with S. haematobium infection, while anaemia was associated with high intensity of S. haematobium (OR = 2.08, p < 0.05) and high hookworm infections OR = 4.75; p < 0.001). The majority of children had eosinophilia, which was significantly associated with high intensity of hookworm infection (OR = 5.34, p < 0.05). Overall 38 % of the children had ultrasound-detectable urinary tract morbidity, which was associated with high intensity of S. haematobium infection (OR = 3.13, p < 0.05).ConclusionPrevalences of S. haematobium and STH infections among the primary school children were high and the parasites were responsible for significant morbidity. A clear synergistic interaction was observed between hookworm and T. trichiura infections. Increased coverage in administration of praziquantel and albendazole in the area is recommended to control morbidity due to these infections.

The Contentious Political Economy of Biofuels

Media headlines and international press coverage have called attention to the Tana River Delta, a small, rural, poor region on Kenya’s eastern coast. In part, these news articles tracked the events around a court case launched by Tana villagers and nongovernmental organizations against several government agencies and a private sugar company. Why did an obscure, local court case in a remote, pastoral community draw international media attention? How did those involved in the case make their claims about the Tana Delta resonate with a wider audience? Proponents and their allies, I argue, linked Tana land-use plans to global debates over biofuels, drawing on language of food security, land tenure, and sovereignty. To explain the tactics of claim-making in the Tana Delta, I offer the hybrid theoretical lens of “contentious political economy”—bringing together contentious politics’ attention to historically based and adaptive claimmaking cycles, political economy’s interest in new markets and private authority, and political ecology’s sensitivity to geography and discourse. By appealing to the contested politics of biofuels, Tana villagers participated in the latest episode of ongoing contestation over land control and exclusion in the global South. The contentious political economy lens reveals how this otherwisemarginalized region ended up at the heart of debates over food security, land rights, and resource conflicts.

Putting a Spin on Jatropha: How Conservationist Rhetoric Drove Bedford Biofuels out of Tana Delta-Kenya

When the Canadian company Bedford Biofuels (BB) started talks with local ranch owners in Tana Delta district (Kenya) about subleasing their land for a large jatropha plantation, they were not the first ones to come to the region for a large-scale agricultural project. Nor were they the first to explore the possibilities of starting a jatropha plantation in Kenya’s coastal area. By the time BB arrived, nature conservation and humanitarian NGOs had firmly established themselves as protectors of the ecologically fragile Tana river delta (now Ramsar site) and its residents, who were argued to be (even more) marginalized by large-scale agricultural projects. During the decision-making process, therefore, BB encountered stiff resistance from local NGOs, which had acquired the experience and the mechanisms to oppose or discourage a large-scale plantation. Additionally, BB was faced with a central government which gradually moved from a pro-jatropha stance to a more critical view of large-scale jatropha cultivation. Nevertheless, most of the local residents as well as the local government administration and the county council supported BB’s plans to establish a large jatropha plantation. Although the deal was struck and the anti-jatropha campaign had ostensibly not prevailed, BB closed its plantation within the year. In the article, we analyze how discursive generalizations about foreign large-scale land acquisitions and in particular about large foreign jatropha plantations gradually undermined the legitimacy of the BB jatropha plantation in Tana Delta. To explore this question, the discussion focuses on analyzing the resources that account for the success of the anti-BB rhetoric and the interests that were involved in its production. These resources have been identified as local to global (I)NGO alliances; the use of e-media as a conduit for opposition rhetoric and the strategic use of rhetorical images and polemic. Each of the three phenomena will be explored for their conceptual dimensions and their rhetorical implications. We argue that the conservationist rhetoric compressed intermediality, the grid where ideologies and practices of different stakeholders intersect. Thus, it effectively narrowed the possibility for non-compatible stakeholders, such as Bedford Biofuels, to avoid conflict. This initiated a gradual erosion of the rationale of the BB jatropha project in Tana Delta, which eventually led to the closure of the jatropha project and the departure of Bedford Biofuels from the area.

Characterizing floods in the poorly gauged wetlands of the Tana River Delta, Kenya, using a water balance model and satellite data

Abstract. Wetlands, such as those of the Tana River Delta in Kenya, are vital but threatened ecosystems. The flooding characteristics of wetlands largely determine their physical, chemical and biological properties, so their quantification is crucial for wetland management. This quantification can be achieved through hydrological modelling. In addition, the analysis of satellite imagery provides essential hydrological data to monitor floods in poorly gauged zones. The objective of this study was to quantify the main water fluxes and flooding characteristics (extent, duration and number of floods) in the poorly gauged Tana River Delta in East Africa during 2002–2011. To do so, we constructed a lumped hydrological model (the Tana Inundation Model, TIM) that was calibrated and validated with MODIS data. Further analysis of the MYD09A1 500 m composite product provided a map of the empirical probability of flooded state. In non-extreme years and for the current topology of the delta, the flood extent exceeded 300 km2. Floods over 200 km2 occurred on average once a year, with a mean duration of 18 days. River discharge from the upper basin counted for over 95% of the total water inflow. The results are discussed in the light of possible improvements of the models and wetland management issues. This study provides the first known quantification of spatial and temporal flooding characteristics in the Tana River Delta. As such, it is essential for the water and natural resource management of the Tana River basin. The water balance approach was pertinent to the study of this system, for which information on its internal properties and processes is limited. The methodology, a combination of hydrological modelling and flood mapping using MODIS products, should be applicable to other areas, including those for which data are scarce and cloud cover may be high, and where a medium spatial resolution is required.

Floods and livelihoods: The impact of changing water resources on wetland agro-ecological production systems in the Tana River Delta, Kenya

Wetlands are highly dynamic and productive systems that have been under increased pressure from changes in land use and water management strategies. In Eastern Africa, wetlands provide resources at multiple spatial and temporal levels through farming, fishing, livestock ownership and a host of other ecosystem services that sustain the local economy and individual livelihoods. As part of a broader effort to describe future development scenarios for East African coastal wetlands, this qualitative study focuses on understanding the processes by which river water depletion has affected local food production systems in Kenya's Tana River Delta over the past 50 years, and how this situation has impacted residents’ livelihoods and well-being. Interviews performed in six villages among various ethnic groups, geographical locations and resource profiles indicated that the agro-ecological production systems formerly in place were adapted to the river's dynamic flooding patterns. As these flooding patterns changed, the local population diversified and abandoned or adopted various farming, fishing and livestock-rearing techniques. Despite these efforts, the decrease in water availability affected each subcomponent of the production systems under study, which led to their collapse in the 1990s. Water depletion negatively impacted local human well-being through the loss of food security. The current study provides a detailed account of the dynamics of agro-ecological production systems facing the effects of river water depletion in a wetland-associated environment in Sub-Saharan Africa.

Rediscovery of Boulengerula denhardti Nieden 1912 (Amphibia: Gymnophiona: Caeciliidae) in Meru County, Kenya

The dearth of information on caecilian amphibians is most likely due to a lack of directed field studies. Here we report the rediscovery of a population of Boulengerula denhardti nearly a century after its description by Nieden in 1912. Morphological examination of seven specimens suggests that they are closer to the type of B. denhardti than to any other member of the genus. Nieden’s type locality has been widely interpreted as the Tana River Delta, although searches there have not revealed specimens of this species. The locality of the material described herein comes from Ngaia Forest, Meru County, Kenya, approximately 420 km, northwest of the Tana Delta. We discuss dispersal in caecilians and their likely use of riverine corridors.We speculate that more species in this genus are likely to be found in Kenya.

Rediscovery ofBoulengerula denhardtiNieden 1912 (Amphibia: Gymnophiona: Caeciliidae) in Meru County, Kenya

The dearth of information on caecilian amphibians is most likely due to a lack of directed field studies. Here we report the rediscovery of a population of Boulengerula denhardti nearly a century after its description by Nieden in 1912. Morphological examination of seven specimens suggests that they are closer to the type of B. denhardti than to any other member of the genus. Nieden's type locality has been widely interpreted as the Tana River Delta, although searches there have not revealed specimens of this species. The locality of the material described herein comes from Ngaia Forest, Meru County, Kenya, approximately 420 km, northwest of the Tana Delta. We discuss dispersal in caecilians and their likely use of riverine corridors. We speculate that more species in this genus are likely to be found in Kenya.

Dispersal distance of rice (Oryza Sativa L.) pollen at the Tana River delta in the coast province, Kenya

Rice is a staple food in Kenya and its production needs to be increased. Genetically modified (GM) rice may be a solution, but before it can be introduced, potential ecological impacts, such as pollen mediated gene flow from GM rice to non-GM rice or to its wild indigenous relatives, need to be understood. Pollen dispersal in rice (Oryza sativa) was studied in the Tana River district in the coast province of Kenya. O. sativa seedlings were planted in a 50 m diameter circular experimental design. Pollen traps (glass slides coated by vaseline attached to a board) were used to measure pollen flow at 2 heights and at increasing distances from the source plot. Pollen dispersal decreased rapidly with increasing distance from the pollen source up to 250 m, no pollen was found at 300 m. There was a significant (P 0.05) in pollen count between upper and lower pollen traps. The highest daily pollen count was observed between 11:00 am and 12:00 noon, and at a narrow range of temperatures 28 ± 2oC. On the basis of these data, an adequate isolation distance of more than 250 m should be considered to minimize chances of gene flow from transgenic rice to conventional or wild rices.

Primate census and habitat evaluation in the Tana delta region, Kenya

AbstractNineteen indigenous forest patches in the Tana River delta region, Kenya were surveyed between October and November 2000 for primates and habitat disturbance. Special emphasis was placed on the endangered Tana River red colobus (Procolobus rufomitratus Peters) and crested mangabeys (Cercocebus galeritus galeritus Peters), both of which are endemic to the region. Habitat disturbances evident in the forests included cutting of trees, harvesting of thatching material, firewood collection, dyke construction, cultivation, palm wine tapping and charcoal burning. A total of 85 groups of five primate species were counted. These comprised eighteen, ten, 22, 31 and four groups of red colobus, crested mangabey, baboons (Papio cynocephalus L.), sykes monkeys (Cercopithecus mitis Wolf) and vervet monkeys (Cercopithecus aethiops L.), respectively. A wider distribution of red colobus and crested mangabeys than was documented previously was noted, implying that they are probably more abundant than hitherto reported. It is hypothesized that extensive studies on some fauna considered endangered world‐wide would probably redefine their conservation status. Future studies in the lower Tana River region should cover the previously unsurveyed forests and focus on ways of curbing forest destruction.