Bio

Dr. OLAKA, Lydia Atieno

Education

PreviewAttachmentSize
CV99.43 KB

Publications


2018

Muhati, GL, Olaka L, Olago D.  2018.  Participatory scenario development process in addressing potential impacts of anthropogenic activities on the ecosystem services of MT. Marsabit forest, Kenya. Global Ecology and Conservation. 14:e00402. AbstractFull Text

The Marsabit Forest Reserve (MFR), a green island in an arid environmental setting, generates multiple ecosystem goods and services (ES) to the local community critical for their livelihoods. The forest has been experiencing substantial land conversion for town expansion, agriculture production and settlements threatening long-term ES provision. Sustaining the forest ES under increasing anthropogenic pressures is one of the great challenges of the Marsabit forest community. We used focus group discussions in the thirteen locations around the forest and individual key informant's interviews in the identification of drivers of change and their potential impacts on ES in MFR. We used the scenario development process (SDP) in coming up with four divergent but plausible exploratory scenarios. The study established that the main ES provided by the forest was, water, fuelwood, forage (dry season grazing resource), medicinal plants and timber for construction. Stakeholders identified population pressure, unsustainable utilisation of forest resources, institutional barriers to effective resource management, land use and climate change as the main drivers impacting ES provision in the forest. Land use change and climate change were considered the most significant drivers yet the most uncertain in the future impacting ES provision in the MFR. The SDP identified four alternative future scenarios for the MFR by the year 2043 with the Marsabit we want scenario identified as the most desirable future for the sustainable supply of ES with adequate adaptation to observed changes. Stakeholders came up with a joint action plan implementation matrix for the identified scenario while mitigating the negative aspects of the alternative scenarios. The results support the need for participatory land use planning that takes into to account the growing threat of climate change to natural forest systems.

Muhati, GL, Olago D, Olaka L.  2018.  Quantification of carbon stocks in Mount Marsabit Forest Reserve, a sub-humid montane forest in northern Kenya under anthropogenic disturbance. Global Ecology and Conservation. 14 AbstractFull Text

The quantification of carbon stocks is vital for decision making in forest management, carbon stock change assessment and scientific applications. We applied the land degradation surveillance framework (LDSF) method with a sentinel site of (10 km × 10 km) to assess carbon stock levels and tree diversity in the Marsabit Forest Reserve (MFR). The above ground (ABG) carbon stock was estimated at 12.42 t/ha, while soil organic carbon (SOC) was 12.51 t/ha, with SOC densities increasing with increasing depth. The mean ABG carbon and SOC densities were higher in the least disturbed strata than the disturbed strata. The estimated ABG carbon and SOC stocks were significantly lower than the range observed in a typical dry tropical forest. Twenty-one tree species were recorded belonging to twelve families with the disturbed areas recording nine tree species while the least disturbed recording twelve species. Rubiaceae and Rutaceae were the richest families with four species each while Boraginaceae, Capparaceae, Flacourtiaceae, Tiliaceae, Violaceae, and Ochnaceae the least frequent with one species each. The most common tree species were, Croton megalocarpus, Drypetes gerrardii, Ochna insculpta, Strychnos henningsii and Vangueria madagascariensis. The forest recorded a basal diameter of 14.09 ± 12.15 cm, basal area of 0.016 m 2/ha with a mean height of 8.69 m. The basal size class distribution declined monotonically indicative of a stable population. Livestock grazing, selective logging, and firewood collection were the primary forms of anthropogenic activities recorded in the MFR despite the moratorium imposed on consumptive utilisation of forest products by the Marsabit County security committee. The Pearson correlation coefficient returned an inverse relationship between forest disturbance with SOC and ABG carbon in the disturbed strata suggesting that anthropogenic activities reduced carbon stocks in the MFR. Concerted efforts to mitigate anthropogenic impacts on the MFR could significantly increase its terrestrial carbon sequestration potential and the provision of critical ecosystem goods and services.

Cuni-Sanchez, A, Omeny P, Pfeifer M, Olaka L, Mamo MB, Marchant R, Burgess ND.  2018.  Climate change and pastoralists: perceptions and adaptation in montane Kenya. Climate and Development. :1-12. AbstractFull Text

Tropical montane forests are amongst the most threatened ecosystems by climate change. However, little is known about climatic changes already observed in these montane areas in Africa, or the adaptation strategies used by pastoralist communities. This article, focused on three mountains in northern Kenya, aims to fill these knowledge gaps. Focus-group discussions with village elders were organized in 10 villages on each mountain (n = 30). Villages covered different pastoralist ethnic groups. Historical data on rainfall, temperature and fog were gathered from Marsabit Meteorological station. All participants reported changes in the amount and distribution of rainfall, fog, temperature and wind for the past 20–30 years; regardless of the mountain or ethnicity. They particularly highlighted the reduction in fog. Meteorological evidence on rainfall, temperature and fog agreed with local perceptions; particularly important was a 60% reduction in hours of fog per year since 1981. Starting farming and shifting to camel herding were the adaptive strategies most commonly mentioned. Some adaptive strategies were only mentioned in one mountain or by one ethnic group (e.g. starting the cultivation of khat). We highlight the potential use of local communities’ perceptions to complement climatic records in data-deficient areas, such as many tropical mountains, and emphasize the need for more research focused on the adaptation strategies used by pastoralists.

2016

Olaka, LA, Wilke FDH, Olago DO, Odada EO, Mulch A, Musolff A.  2016.  Groundwater fluoride enrichment in an active rift setting: Central Kenya Rift case study. Science of the Total Environment. 545(1):641-653. AbstractFull Text

Groundwater is used extensively in the Central Kenya Rift for domestic and agricultural demands. In these active rift settings groundwater can exhibit high fluoride levels. In order to address water security and reduce human exposure to high fluoride in drinking water, knowledge of the source and geochemical processes of enrichment are required. A study was therefore carried out within the Naivasha catchment (Kenya) to understand the genesis, enrichment and seasonal variations of fluoride in the groundwater. Rocks, rain, surface and groundwater sources were sampled for hydrogeochemical and isotopic investigations, the data was statistically and geospatially analyzed. Water sources have variable fluoride concentrations between 0.02–75 mg/L. 73% exceed the health limit (1.5 mg/L) in both dry and wet seasons. F− concentrations in rivers are lower (0.2–9.2 mg/L) than groundwater (0.09 to 43.6 mg/L) while saline lake waters have the highest concentrations (0.27–75 mg/L). The higher values are confined to elevations below 2000 masl. Oxygen (δ18O) and hydrogen (δD) isotopic values range from − 6.2 to + 5.8‰ and − 31.3 to + 33.3‰, respectively, they are also highly variable in the rift floor where they attain maximum values. Fluoride base levels in the precursor vitreous volcanic rocks are higher (between 3750–6000 ppm) in minerals such as cordierite and muscovite while secondary minerals like illite and kaolinite have lower remnant fluoride (< 1000 ppm). Thus, geochemical F− enrichment in regional groundwater is mainly due to a) rock alteration, i.e. through long residence times and natural discharge and/or enhanced leakages of deep seated geothermal water reservoirs, b) secondary concentration fortification of natural reservoirs through evaporation, through reduced recharge and/or enhanced abstraction and c) through additional enrichment of fluoride after volcanic emissions. The findings are useful to help improve water management in Naivasha as well as similar active rift setting environments.

Dommain, R, S Riedl ALD, deMenocal PB, Olaka LA, Strecker MR, Potts R.  2016.  Lake level history of Paleolake Siriata and hydrological sub-basin connectivity in the Southern Kenya Rift during the African Humid Period (AHP), December 2016. American Geophysical Union, Fall General Assembly 2016. , San Fransisco Abstract

The AHP is one of the most dramatic examples of late Quaternary hydroclimatic change in the tropics. During this wet period numerous large and deep lakes existed in the eastern arm of the East African Rift System (EARS) as testified by paleo-shorelines and lacustrine sediments. The tempo of onset and termination as well as the duration of the AHP is a matter of ongoing research and are still poorly established for the Southern Kenya Rift. Here we present new paleo-shoreline and sedimentary evidence for the existence of a freshwater lake during the AHP to the east of alkaline Lake Magadi. The AHP lake - Paleolake Siriata - was a critical link in the paleodrainage network that connected the central with the southern Kenya rift lakes and northern Tanzania. To establish the timing and spatial extent of Paleolake Siriata we mapped elevations of paleo-shorelines and associated shoreline facies and diatomaceous lacustrine sediments along the former basin margins. Morphometric and topographic details were mapped using a dGPS and an UAV to create a DEM with a resolution of 5 cm to define shoreline elevations and the characteristics of the former basin outlet. Reservoir age-corrected radiocarbon dates of gastropod and bivalve shells and 40Ar/39Ar ages of pumice from the lacustrine strata provide the chronological framework of the Lake Siriata highstand. In addition, oxygen-isotope measurements of gastropod shells indicate past variations in the former lake water-balance. Paleolake Siriata formed abruptly immediately after the dry Younger Dryas interval and reached a maximum depth of 55 m and a surface area of 30 km2; during highstand conditions the lake overflowed into adjacent Lake Magadi while it received inflow from Lake Naivasha via the Kedong Valley and the Olorgesailie Basin in the north. This hydrological connectivity provides important context for the interpretation of the sediment records from the recently collected Olorgesailie-Koora and Lake Magadi drill cores.

2015

Olaka, LA.  2015.  How Closed are Closed Lakes in Rifts? Significance of Hydraulic Gradients for the Budgets of Paleo-Lakes in East Africa, December 2015 American Geophysical Union, Fall Meeting 2015. , San Fransisco Abstract

The hydrogeology of rift lakes is complex due to the potential influence of faults and porous volcanic and volcanoclastic media on groundwater flow. We conducted a comprehensive study that integrated geological and hydrogeological data as well as the application of a linear decay model to estimate the groundwater flow between the two of the best-studied lake systems in East Africa, the adjacent Lakes Naivasha and Nakuru- Elmenteita in the Central Kenya Rift. Whereas both lake basins host relatively shallow lakes today, paleo-shorelines and sediments suggest >100 m deep lakes during a wetter climate during the Early Holocene during the so-called African Humid Period. Stable isotope data show variations form highly depleted to more enriched d18O waters. The linear-reservoir depletion model simulates the decline of the Early Holocene lakes in both basins to the modern levels. The altitude difference of ca. 100 m of both paleo-lake levels enables us to estimate the duration of the groundwater decline and the connectivity of the two basins via the Eburru/Gilgil barrier. The results suggest a decline of the groundwater levels during ca. 5 kyrs if there is no recharge, and between 2-2.7 kyrs based on the modern recharge of 0.52 m/yr as the end members of the delay time introduced by subsurface water flow to the hydrology of the lake system. The latter value suggests that ca. 40.95 cubic kilometres of water flowed from Lake Naivasha to Nakuru- Elmenteita at maximum lake level in the Early Holocene following the hydraulic gradient concurrent to the topographic slope. The unexpectedly large volume, more than half of the volume of the paleo-Lake Naivasha during the Early Holocene, emphasizes the importance of groundwater in hydrological modelling of paleo-lakes in rifts. Moreover, the subsurface connectivity of rift lakes also causes a significant lag time to the system introducing a nonlinear component to the system that has to be considered while interpreting paleo-lake records.

Baker, T, Kiptala J, Olaka L, Oates N, Hussain A, McCartney M.  2015.  Baseline review and ecosystem services assessment of the Tana River Basin, Kenya. Baseline review and ecosystem services assessment of the Tana River Basin, Kenya. : International Water Management Institute (IWMI) Abstract

The 'WISE-UP to climate'project aims to demonstrate the value of natural infrastructure as a
'nature-based solution'for climate change adaptation and sustainable development. Within
the Tana River Basin, both natural and built infrastructure provide livelihood benefits for
people. Understanding the interrelationships between the two types of infrastructure is a
prerequisite for sustainable water resources development and management. This is
particularly true as pressures on water resources intensify and the impacts of climate change
increase. This report provides an overview of the biophysical characteristics, ecosystem
services and links to livelihoods within the basin.

2014

2012

Stoof-Leichsenring, KR, Junginger A, Olaka LA, Tiedemann R, Trauth MH.  2012.  Natural environmental variability and anthropogenic overprint in the Lake Naivasha Basin Central Kenya Rift: A diatom record over the last two centuries. AbstractNatural environmental variability and anthropogenic overprint in the Lake Naivasha Basin Central Kenya Rift: A diatom record ove

Lake Naivasha, Kenya, is one of a number of freshwater lakes in the East African Rift System. Since the beginning of the twentieth century, it has experienced greater anthropogenic influence as a result of increasingly intensive farming of coffee, tea, flowers, and other horticultural crops within its catchment. The water-level history of Lake Naivasha over the past 200years was derived from a combination of instrumental records and sediment data. In this study, we analysed diatoms in a lake sediment core to infer past lacustrine conductivity and total phosphorus concentrations. We also measured total nitrogen and carbon concentrations in the sediments. Core chronology was established by 210Pb dating and covered a ~186-year history of natural (climatic) and human-induced environmental changes. Three stratigraphic zones in the core were identified using diatom assemblages. There was a change from littoral/epiphytic diatoms such as Gomphonema gracile and Cymbella muelleri, which occurred during a prolonged dry period from ca. 1820 to 1896 AD, through a transition period, to the present planktonic Aulacoseira sp. that favors nutrient-rich waters. This marked change in the diatom assemblage was caused by climate change, and later a strong anthropogenic overprint on the lake system. Increases in sediment accumulation rates since 1928, from 0.01 to 0.08gcm−2year−1 correlate with an increase in diatom-inferred total phosphorus concentrations since the beginning of the twentieth century. The increase in phosphorus accumulation suggests increasing eutrophication of freshwater Lake Naivasha. This study identified two major periods in the lake’s history: (1) the period from 1820 to 1950 AD, during which the lake was affected mainly by natural climate variations, and (2) the period since 1950, during which the effects of anthropogenic activity overprinted those of natural climate variation.

2011

Stoof, KR, Junginger A, Olaka LA, Tiedemann R, Trauth MH.  2011.  Natural environmental variability and anthropogenic overprint in the Lake Naivasha Basin Central Kenya Rift: A diatom record over the last two centuries. Journal of Paleolimnology. 45:353-367.

2010

Trauth, MH, Maslin MA, Deino A, Junginger A, Lesoloyia M, EO O, Olago DO, Olaka L, Strecker MR.  2010.  Human evolution in a variable environment: The amplifier lakes of Eastern Africa.
Olaka, LA, Odada EO, Trauth MH, Olago DO.  2010.  The Sensitivity of East African rift lakes to climate fluctuations. Journal of Paleolimnology. 44:629-644.

2007

Olago, D, Marshall M, Wandiga SO, Opondo M, Yanda PZ, Kangalawe R, Githeko A, Downs T, Opere A, Kabumbuli R, Kirumira E, Ogallo L, Mugambi P, Apindi E, Githui F, Kathuri J, Olaka L, Sigalla R, Nanyunja R, Baguma T, Achola P.  2007.  Climatic Socio-economic and Health Factors Affecting Human Vulnerability to Cholera in the Lake Victoria Basin East Africa. AMBIO: A Journal of the Human Environment. 36:350–358.

UoN Websites Search