Geochemistry of groundwater of shallow coastal aquifers of Eastern Dahomey Basin, Southwestern Nigeria

Coastal basins offer valuable land, water and economic resources and have high economic contribution to national and global development; hence the high population of coastal cities around the world due to their commercial, industrial and agricultural significance. Some of the cities and towns situated in coastal parts of Africa rely on the freshwater of the coastal aquifers to meet the vast shortage in water supply resulting from infrastructural deficiency and decay. Complexity of groundwater occurrence and distribution in basement aquifers lead most of the developing countries to depending on basins to meet their daily water demand as these basins are known for high freshwater potential. The Eastern Dahomey Basin (EDB) is not an exemption. The high rate of population growth, unpredictable rainfall patterns, rise in sea-levels, coupled with over abstraction and seawater intrusion, land use activities, climate conditions, and the geological setting have significant influence on groundwater chemistry and quality. Recently, groundwater resources management has become preferentially higher in the agenda of the sustainable development goal of the United Nations with much attention on developing countries where groundwater remains their source of water demand for various usages. As data and information on groundwater is critical to its sustainable management, especially at a basin scale. This study presents a comprehensive groundwater geochemistry of the Eastern Dahomey basin to contribute to the amount of knowledge available to better increase the effective framework of integrated water resources management in Sub-Saharan Africa. A total of 230 water samples were collected between May 2017 and April 2018, a period which spanned through wet and dry seasons, from the shallow boreholes and hand-dug wells. These 230 groundwater samples (97 in wet season and 133 in dry season) were analysed for essential water quality parameters such as pH, Electrical Conductivity (EC), Total Dissolved solid (TDS), Total Hardness (TH), Ca, Mg, Na, K, HCO3, Cl, SO4, NO3, F and the trace metals As, Cd, Fe, Mn, Pb and Si and stable Environmental Isotopes of δ18O and δ2H. In addition to these, stable isotopes of δ18O and δ2H in precipitation data from three selected GNIP stations, Douala, Cotonou and Kano within the West Africa, were collected for comparative analysis. These data were subjected to evaluation for different quality indices such as GQIswi, SMI, GWQI and ionic ratios, while modelling, plotting and statistical were carried out using analysis using ArcGIS, MATLAB, Geochemist Workbench, SPSS, Origin pro and Microsoft Excel. Electrical resistivity prospecting and borehole logging were carried out in locations with enhanced electrical conductivity around the coastal communities. Three traverses A-B, C-D and E-F were selected along which ERT and IP were carried out in directions perpendicular and parallel to the coastline and correlated with borehole logs. Higher salinities above 1000 μS/cm were observed in wells located around communities in Seme, Lekki, Eleko, Okun-Ajah, Ode-Mahin and Igbokoda. HFE-D revealed that mixed groundwater of Na+Ca-HCO3, Na-Cl and Ca-Cl dominate the area due to gravity-driven flow leading to groundwater freshening inland from the coastline towards the northern part of the basin. The groundwater quality index from SMI and GQIswi show areas within 3 km from the coastline that are more sensitive vulnerable to seawater intrusion. This result therefore guided our selection of areas for electrical resistivity geophysical investigation. Electrical resistivity tomography (ERT) and induced polarisation (IP) indicated a saline water-saturated layer of fine-grained sand and silty clay which is overlaid by the unconsolidated unconfined freshwater aquifer in area around Lekki and Okun Ajjah while low resistivity of clay lenses were found at Igbokoda, Ugbonla and Ode-Mahin. Correlation of selected ERT results with borehole logs further affirmed the suspected lithology from the sections. Results of the hydrochemical model revealed Ca-HCO3 and Na-Cl as dominant water types with other mixing water types such as Ca-SO4, Ca-Cl, Na-SO4 and K-Mg-HCO3 which characterised early stage of groundwater transformation in the shallow coastal basin. In addition, a comparison of the δ18O and δ2H isotopic compositions of groundwater and precipitation in the three selected stations, with their respective D-excess values established low evapotranspiration induced isotope enrichment, which could be due to higher precipitation and humidity in the region resulting in low isotope fractionation, hence, little effect of seasonal variations. Assessing the future use of groundwater for irrigation suggests some parts of the aquifer may have unsuitable quality based on the percentage sodium (%Na), Kelly’s ratio (KR), magnesium ratio (MR) and total hardness. Results of GQWI revealed 44.8, 22.9 and 12.5% of water samples during the wet season fell in the class of excellent, good and moderate quality respectively, while 8.3 %, 1.0 and 10.4 % fell in a class of poor, very poor and nonpotable water quality. Correlating the spatial distribution of the GWQI with the land use pattern map of the area revealed the least potable water is clustered around settlement areas, indicating groundwater quality has been impacted by municipal, industrial and agricultural waste. The linear regression modelling established significant relationships between SWL, SO42−, NO3−, Fe, and Eh for both wet and dry seasons with the p-value falling between 75% and 95%, which can also be seen in the plots of Eh/ORP against Fe2+, Mn2+, SO42−, and NO3−. This study has identified groundwater quality deterioration within the shallow coastal aquifers of the eastern Dahomey basin. Hydrochemical and geophysical approach established saltwater intrusion into freshwater aquifer occurred both as seawater intrusion, dissolution of evaporites within the clay lenses and sea spraying within the close proximity to the sea. Hydrochemical and environmental Isotopes classified as young from a meteoric source, which is still in the early stage of geochemical evolution with short residence time. A combination of groundwater quality indices (GWQI) and biogeochemical (redox) analysis also established the influence of natural and anthropogenic effect of climate change, urbanisation, industrialisation and agriculture on the groundwater quality of the basin. The present study provides information of value to planners and policy-makers for the sustainable management and protection of coastal groundwater resources in the Eastern Dahomey Basin. There is a need for waste management policy review and enforcement to support sustainable groundwater resource management and sustainable development goal number 6 (SDG6). Keywords: Groundwater; Saltwater intrusion; Groundwater quality index; freshwater; Coastal aquifer; Clay lenses; Saline water; Freshwater; Geoelectrical Layers; Hydrogeochemistry; mineral dissolution; Saturation Index; Stable Isotopes; Environmental Isotopes; Precipitation; Groundwater Origin; Residence time; Climate change; Biogeochemical Processes; Redox and Metals mobilisation; land use; seasonal effects; Anthropogenic; water resource management.Coastal basins offer valuable land, water and economic resources and have high economic contribution to national and global development; hence the high population of coastal cities around the world due to their commercial, industrial and agricultural significance. Some of the cities and towns situated in coastal parts of Africa rely on the freshwater of the coastal aquifers to meet the vast shortage in water supply resulting from infrastructural deficiency and decay. Complexity of groundwater occurrence and distribution in basement aquifers lead most of the developing countries to depending on basins to meet their daily water demand as these basins are known for high freshwater potential. The Eastern Dahomey Basin (EDB) is not an exemption. The high rate of population growth, unpredictable rainfall patterns, rise in sea-levels, coupled with over abstraction and seawater intrusion, land use activities, climate conditions, and the geological setting have significant influence on groundwater chemistry and quality. Recently, groundwater resources management has become preferentially higher in the agenda of the sustainable development goal of the United Nations with much attention on developing countries where groundwater remains their source of water demand for various usages. As data and information on groundwater is critical to its sustainable management, especially at a basin scale. This study presents a comprehensive groundwater geochemistry of the Eastern Dahomey basin to contribute to the amount of knowledge available to better increase the effective framework of integrated water resources management in Sub-Saharan Africa. A total of 230 water samples were collected between May 2017 and April 2018, a period which spanned through wet and dry seasons, from the shallow boreholes and hand-dug wells. These 230 groundwater samples (97 in wet season and 133 in dry season) were analysed for essential water quality parameters such as pH, Electrical Conductivity (EC), Total Dissolved solid (TDS), Total Hardness (TH), Ca, Mg, Na, K, HCO3, Cl, SO4, NO3, F and the trace metals As, Cd, Fe, Mn, Pb and Si and stable Environmental Isotopes of δ18O and δ2H. In addition to these, stable isotopes of δ18O and δ2H in precipitation data from three selected GNIP stations, Douala, Cotonou and Kano within the West Africa, were collected for comparative analysis. These data were subjected to evaluation for different quality indices such as GQIswi, SMI, GWQI and ionic ratios, while modelling, plotting and statistical were carried out using analysis using ArcGIS, MATLAB, Geochemist Workbench, SPSS, Origin pro and Microsoft Excel. Electrical resistivity prospecting and borehole logging were carried out in locations with enhanced electrical conductivity around the coastal communities. Three traverses A-B, C-D and E-F were selected along which ERT and IP were carried out in directions perpendicular and parallel to the coastline and correlated with borehole logs. Higher salinities above 1000 μS/cm were observed in wells located around communities in Seme, Lekki, Eleko, Okun-Ajah, Ode-Mahin and Igbokoda. HFE-D revealed that mixed groundwater of Na+Ca-HCO3, Na-Cl and Ca-Cl dominate the area due to gravity-driven flow leading to groundwater freshening inland from the coastline towards the northern part of the basin. The groundwater quality index from SMI and GQIswi show areas within 3 km from the coastline that are more sensitive vulnerable to seawater intrusion. This result therefore guided our selection of areas for electrical resistivity geophysical investigation. Electrical resistivity tomography (ERT) and induced polarisation (IP) indicated a saline water-saturated layer of fine-grained sand and silty clay which is overlaid by the unconsolidated unconfined freshwater aquifer in area around Lekki and Okun Ajjah while low resistivity of clay lenses were found at Igbokoda, Ugbonla and Ode-Mahin. Correlation of selected ERT results with borehole logs further affirmed the suspected lithology from the sections. Results of the hydrochemical model revealed Ca-HCO3 and Na-Cl as dominant water types with other mixing water types such as Ca-SO4, Ca-Cl, Na-SO4 and K-Mg-HCO3 which characterised early stage of groundwater transformation in the shallow coastal basin. In addition, a comparison of the δ18O and δ2H isotopic compositions of groundwater and precipitation in the three selected stations, with their respective D-excess values established low evapotranspiration induced isotope enrichment, which could be due to higher precipitation and humidity in the region resulting in low isotope fractionation, hence, little effect of seasonal variations. Assessing the future use of groundwater for irrigation suggests some parts of the aquifer may have unsuitable quality based on the percentage sodium (%Na), Kelly’s ratio (KR), magnesium ratio (MR) and total hardness. Results of GQWI revealed 44.8, 22.9 and 12.5% of water samples during the wet season fell in the class of excellent, good and moderate quality respectively, while 8.3 %, 1.0 and 10.4 % fell in a class of poor, very poor and nonpotable water quality. Correlating the spatial distribution of the GWQI with the land use pattern map of the area revealed the least potable water is clustered around settlement areas, indicating groundwater quality has been impacted by municipal, industrial and agricultural waste. The linear regression modelling established significant relationships between SWL, SO42−, NO3−, Fe, and Eh for both wet and dry seasons with the p-value falling between 75% and 95%, which can also be seen in the plots of Eh/ORP against Fe2+, Mn2+, SO42−, and NO3−. This study has identified groundwater quality deterioration within the shallow coastal aquifers of the eastern Dahomey basin. Hydrochemical and geophysical approach established saltwater intrusion into freshwater aquifer occurred both as seawater intrusion, dissolution of evaporites within the clay lenses and sea spraying within the close proximity to the sea. Hydrochemical and environmental Isotopes classified as young from a meteoric source, which is still in the early stage of geochemical evolution with short residence time. A combination of groundwater quality indices (GWQI) and biogeochemical (redox) analysis also established the influence of natural and anthropogenic effect of climate change, urbanisation, industrialisation and agriculture on the groundwater quality of the basin. The present study provides information of value to planners and policy-makers for the sustainable management and protection of coastal groundwater resources in the Eastern Dahomey Basin. There is a need for waste management policy review and enforcement to support sustainable groundwater resource management and sustainable development goal number 6 (SDG6). Keywords: Groundwater; Saltwater intrusion; Groundwater quality index; freshwater; Coastal aquifer; Clay lenses; Saline water; Freshwater; Geoelectrical Layers; Hydrogeochemistry; mineral dissolution; Saturation Index; Stable Isotopes; Environmental Isotopes; Precipitation; Groundwater Origin; Residence time; Climate change; Biogeochemical Processes; Redox and Metals mobilisation; land use; seasonal effects; Anthropogenic; water resource management

Landscape Architecture Framed from an Environmental and Ecological Perspective

Landscape architecture involves designing, planning, and managing natural and built environments. Its goal is to balance natural spaces with the human element. As such, new methods and analysis techniques are necessary for creating healthy and user-friendly spaces in both urban developments and natural environments. This book discusses these approaches to planning and designing natural spaces with a focus on sustainability

Assessing the effects of urban development and climate change on flooding in the Greater Port-Harcourt watershed, Niger Delta, Nigeria

Developing countries have been rapidly urbanising over the last decades, resulting in major environmental pressures and increased vulnerability to natural disasters. A complex combination of factors, including climate change, land use change, poorly implemented regulation and a lack of integrated planning has often resulted in environmental degradation and disproportionate impacts of natural disasters affecting millions worldwide, particularly in tropical cities. The main aim of this study is to understand the effects of land-use and climate change on flooding in the Greater Port-Harcourt watershed. The specific research objectives were: to understand the historical and future land use /land cover changes; to understand the magnitude of change in hydrologic and hydraulic conditions due to land-use and climate changes; to assess the influence of different forest mitigation scenarios on peak-discharge; and to make recommendations on how to improve future planning using insights from this study. Methodologically, the post-classification change detection method was applied to examine the extent and nature of historical LULC changes using remotely sensed data. Future LULC changes were estimated by superimposing the 2060 digitised Masterplan map on the year 2003 baseline imagery. Hydrologic changes were assessed using HEC-HMS model, while changes in the hydraulic condition were assessed using HEC-RAS model. Model output was further used to map flood hazards, flood zones and damage potential. Priority areas and infrastructure at risk were identified by means of their location in flood zones and exposure to floods with high damage potential. On the extent of change, this study revealed that urbanisation and loss of agricultural land had been the dominant and intensive land use change in the watershed. Urbanisation is projected to almost double its 2003 extent by 2060 and is likely to remain the dominant force of land use change. On the nature of change, this study found that urban land was the most dynamic in terms of gross gain and net change. It exhibited the grossest gain (about 9% of the watershed) and the grossest loss leading to a high net change of about 8.6%. In fact, the most prominent transition was the conversion of agricultural land (about 422km2) to urban land, and roughly 93.3% of all conversions to urban land resulted from agricultural land. On the process of change, urban land mainly experienced a net-type of change (change in quantity), whereas changes in agricultural land was more of a swap-type of change (change in location). Importantly, the study reveals that the impact on flood flow was historically significant (about 68%) and is projected to amplify in future, however, these changes are largely attributed to increased storm size. Urbanisation is likely to have little or no impact on annual maximum peak flow at the watershed scale; however, urbanisation is projected to have a considerable impact on peak flow in a number of subbasins, which could have severe implications for flash flooding in those subbasins. Similarly, afforestation could have little or no impact on future maximum peak flow when assessed at the watershed scale. Although some subbasins experienced changes in peak flow, the effect of forest is variable. The study concludes that although the impact of urbanisation is projected to be insignificant at the watershed scale, it could also increase flood risk due to increasing developments in floodplains and channel encroachment. Priority infrastructure and areas requiring urgent flood risk management include the Port-Harcourt seaports, Onne seaport, the University of Science and Technology and cement factory. Priority areas in the Masterplan are mainly in the south (Phase 3), comprising of the Air force base and the residential area near Onne seaport. Lastly, approximately 8.1km and 189m of road and rail network are at greater risk of flooding by means of their exposure to floods with the highest damage potential. Based on this study, I have furthered understanding by showing that the transition to urban land category was dominated by net changes (i.e. changes in quantity). I have also furthered understanding by showing that substantial changes in future urban land-use may not have significant effect on flood parameters. My main contribution to knowledge is that despite the high rate of urbanisation in the GPH watershed and its minimal impact on flooding (which could be due the large size of the storm and watershed), urbanisation could still increase flood risk due to greater exposure of elements at risk in the flood plains to damaging floods. Based on the results, the study recommends that the development authorities should integrate both structural measures (mainly for flood defence around existing developments) and non-structural measures (primarily for future developments). For flood risk management research, this study recommends that conclusions about the effects of urbanisation should not be made solely on the basis of changes in hydrology and river hydraulics, however researchers should also consider the exposure of important elements at risk within the floodplains under study to better understand the effects of urbanisation. Moreover, to better understand urbanisation effects on runoff dynamics in other watersheds, this study recommends that research efforts should be concerted in understanding subbasin-scale changes given that the effects of urbanisation are more pronounced in smaller basins

Integrated assessment of soil erosian processes and policy in Oguta Lake watershed IMO state South East Nigeria

PhD ThesisSoil erosion is one of the most severe environmental problems in Nigeria, especially in the south east region of the country. Oguta Lake watershed is one of the affected watersheds in the region because of various human activities in the area. This thesis presents a thorough assessment of soil erosion processes and policy analysis which simultaneously integrates the physical condition, socio-economic context, institutions, and policy reforms in which stakeholders are embedded. Remote Sensing (RS), reconnaissance survey, two modelling assessment techniques (RUSLE and MPSIAC models) were applied to produce land use/land cover dynamics maps and spatial map of soil erosion, and key factors responsible for soil erosion in the location. Review of environmental regulations, semi-structured interview and focus group discussion were applied and analysed using Institutional Analysis and Development (IAD) framework. Land use and land cover changes were significant during the period 1990 – 2014 as 17% of the watershed was shifted to unstable zones and, thus, contributed to soil erosion by water in the watershed. Human activities like sand mining, deforestation, overgrazing and poor crop farming practice contributed significantly to land use/cover dynamics. Consequently, 14% of the forest and pastureland cover was lost due to human activities in the watershed. The spatial soil erosion map showed that severe soil erosion class was 25-36 tonnes/h/year and covered about 18% of the watershed. On the other hand, two (2) focus group discussions and forty-four (44) semi-structured interviews were conducted with the relevant stakeholders. It was observed that poverty and unemployment were the key drivers of land misuses and environmental degradation in the watershed. Based on the Institutional Analysis and Development (IAD) result. For the land ownership and allocation, this study proposes that the powers and influence of the traditional leaders and local government staff in land allocation and ownership in the watershed should be recognised by the government to increase land use compliance as stipulated in the Land Use Act 1978. For the sand mining, this study proposes an alternative arrangement that empowers the state government to have a shared management responsibility of managing sand mining activity in the watershed. For agricultural practice, this study proposes that operational level organisations should be domiciled in the local community where soil erosion is dominant. Women should be empowered with land and have an improved official representation in agricultural management. This would eliminate the barrier of poor communication channel and promote on the ground monitoring of farming activities and compliance among farmers.Tertiary Education Trust Fund (TETFund) and Federal University of Technology Owerri (FUTO

Comparative analysis of effects of climate-smart agriculture practices and conventional agriculture on selected soil physicochemical properties in Nyimba district, Zambia

Background. Many smallholder farmers in the developing world live in adverse poverty and rely on agriculture as their primary source of income and household food. In Zambia, agriculture production is the main activity for people in rural areas of the country. The study evaluated the effects of climate-smart practices: Gliricidia sepium alley cropping, conservation agriculture basin, ripping, and conventional agriculture cropland on selected physicochemical properties of soil among smallholder farmers’ croplands in Nyimba district, Zambia. Materials and Methods. Cropland under conservation agriculture basin, ripping, agroforestry gliricidia alleyed cropping, and conventional agriculture cropland hosting the practices for more than five years were considered for soil sample collection. Thirty (30) composite soil samples were collected: gliricidia alley cropping (n = 6), conservation agriculture ripping (n = 6), basin (n = 6), conventional agriculture one (n = 6), and conventional agriculture two (n = 6) following a zigzag pattern on soil surface depth of 0–30 cm. The collected composite soil samples were analyzed at the University of Zambia Soil Science Laboratory. Soil laboratory results were analyzed with Minitab Statistical Software version 17 for mean squares, standard deviations, and Tukey’s LSD. Results and Discussion. The study revealed significant effects (p <0.05) of gliricidia alley cropping, conservation agriculture ripping, and basin on soil bulk density, porosity, power of hydrogen (pH), cation exchange capacity, available phosphorus, total nitrogen, exchangeable bases sodium, calcium, and potassium. Exchangeable base magnesium was recorded as insignificant across the considered practices off-course with minimal mean variations with conventional agriculture cropland. Conclusion. The study shows that implementing climate-smart agriculture practices has the potential to improve crop productivity per hectare through reclaiming and amending depleted soil physicochemical properties in a mid and long run. This also indicates the importance of climate-smart agricultural practices implementation among smallholder farmers’ cropping fields

Vulnerability of the Nigerian coast and communities to climate change induced coastal erosion

Improving coastal resilience to climate change hazards requires understanding past shoreline changes. As the coastal population grows, evaluation and monitoring of shoreline changes are essential for planning and development. Population growth increases exposure to sea level rise and coastal hazards. Nigeria, where the study is situated, is among the top fifteen countries in the world for coastal population exposure to sea level rise. This study provided a novel lens in establishing a link between social factors and the intensifying coastal erosion along the Akwa Ibom State study coast. The mixed-method approach used in the study to assess the vulnerability of the Nigerian coast and communities to climate change-induced coastal erosion proved to be essential in gathering a wide range of data (physical, socio economic, participatory GIS maps and social learning) that contributed to a more robust and holistic assessment of coastal erosion, which is a complex issue due to the interplay between the human and natural environments. Remotely sensed data was used to examine the susceptibility and coastal evolution of Akwa Ibom State over 36 years (1984 -2020). Longer-term (1984- 2020) and short-term (2015-2020) shoreline change analyses were used to understand coastal erosion and accretion. From 1984-2020, the total average linear regression rate (LRR) was - 2.7+0.18m/yr and from 2015-2020, it was -3.94 +1.28m/yr, demonstrating an erosional trend along the study coast. Although the rate of erosion varies along the study coast, the linear regression rates (LRR) results show a predominant trend of erosion in both the short and longer term. According to the 2022 Intergovernmental Panel on Climate Change report, loss of land, loss of assets, community disruption and livelihood, loss of environmental resources, ecosystem, loss of life, or adverse health impact are all potential risks along the African coast due to climate change – this study shows that these risks are already occurring today. To quantify the anticipated future coastal erosion risk by 2040 along the study coast, the findings in this study show an overall average LRR of -2.73+ 0.99 m/yr which anticipates that coastal erosion will still be prevalent along the coast by 2040. And, given the current global climate change situation, should be expected to be much higher than the current forecasting. This study re-conceptualised the European Environmental Agency Driver-Pressure StateImpact-Response (DPSIR) model to show Hazard-Driver-Pressure-State-Impact ResponseObservation causal linkages to coastal erosion hazards. The results showed how human activities and environmental interactions have evolved through time, causing coastal erosion. Removal of vegetation cover/backstop for residential and agricultural purposes, indicate that human activities significantly contribute to the study area's susceptibility, rapid shoreline changes, and vulnerability to coastal erosion, in addition to oceanic and climate change drivers such as sea level rise and storminess. Risk perception of coastal erosion in the study area was analysed using the rhizoanalytic method proposed by Deleueze. The method demonstrates how connections and movements can be related and how data can be used to show multiplicity, mark and unmark ideas, rupture pre-conceptions and make new connections. This study shows that coastal erosion awareness is insufficient to build a long-term management plan and sustain coastal resilience. The Hino's conceptual model which provides in-depth understanding on planned retreat was used to illustrate migratory and planned retreat for the study coast where relocation has already occurred due to coastal erosion. The result fell within the Self-Reliance quadrant, indicating that people left the risk zone without government backing or retreat plans. Other coastal residents who have not relocated fell within the Hunkered Down quadrant, showing that they are willing to stay in the risk zone and cope with the threat unless the government/environmental agencies relocate them. This study shows that coastal resilience requires adaptive capacity and government support. However, multilevel governance has inhibited government-community dialogue and involvement, increasing coastal erosion vulnerability. The coastal vulnerability index to coastal erosion was calculated using the Analytical Hierarchy Process weightings. It revealed that 67.55% of the study coast falls within the high-very high vulnerability class while 32.45% is within the very low-low vulnerability class. This study developed and combined a risk perception index to coastal erosion (RPIerosion) and participatory GIS (PGIS) mapping into a novel coastal vulnerability index called the integrated coastal erosion vulnerability index (ICEVI). The case study evaluation in Akata, showed an improvement in the overall vulnerability assessment to reflect the real-world scenario, which was consistent with field data. This study demonstrated not only the presence and challenges of coastal erosion in the research area but also the relevance of involvement between the local stakeholders, government and environmental agencies. Thus, showing the potential for the perspectives of the inhabitants of these regions to inform the understanding of the resilience capacity of the people impacted, and importantly to inform future co-design and/or selection of effective adaptation methods, to better support coastal climate change resilience in these communities. Overall, the study provides a useful contribution to coastal erosion vulnerability assessments in data-scarce regions more broadly, where the mixed-methods approach used here can be applied elsewhere

APPLICATION OF GEOPHYSICAL AND GEOCHEMICAL METHODS FOR SOIL CHARACTERISATION IN SUSTAINABLE PRECISION AGRICULTURE IN SELECTED FARMS

All soils have potential for high yield for specific crops. Nigerian soils have potential for medium to high yield, but poor farming practices including the misuse of chemical fertilizers result in a number of constraints such as soil salinity, degradation and declining fertility, which militate against high crop yields. Nigeria, currently battling with food insecurity because population growth is not commensurate with agricultural production. Thus, there is need for urgent intervention in the agricultural sector. The aim of this study was to integrate geophysical and geochemical methods for sustainable precision agriculture in two farm sites of Covenant University and Landmark University, Nigeria. In this study, electrical resistivity, geochemical and satellite imagery methods were used for soil characterisation in farm sites at Covenant University, Ota, Southwest and Landmark University, Omu-Aran, North-central Nigeria between June, 2018 and January, 2019. The electrical resistivity data were processed using RES2DINV and Win-Resist software. Geochemical analysis of soil samples from the sites was conducted using ICP-MS in ACME laboratory, Canada. Monthly MERRA satellite data was used to determine the soil temperature and soil moisture content while soil salinity was estimated from Landsat-8 satellite imagery. The study showed that electrical resistivity of the topsoil in Covenant University farm ranged from 120 -500 Ωm, while that of Landmark University farm ranged from 345-527 Ωm. The soil types delineated at the Covenant University farm were clayey sand and lateritic clay; sand/lateritic gravelly sand was delineated at Landmark University farm. Potentially toxic elements were detected in the soil samples of both sites; arsenic (As), chromium (Cr), lead (Pb) and copper (Cu) exceeded FAO/WHO recommended standard limits in Covenant University farm. The pollution indices of Co, Cr, Ni, Pb and Mn in the Covenant University farm were within low to high contamination, while As was within medium to high contamination. In Landmark University farm, the pollution indices of Pb, Cu, Zn, Co and Cd ranged from low to medium, while As has pollution index within low to high contamination. Results showed elevated concentrations of As in all samples. Ca-Mg, P-Mg, Fe-Al, Ca-K, Mg-K and Na-K paired nutrients were positively correlated at 5% level of significance in both farmlands, indicating similar increase in both farmlands. Also, the geospatial maps revealed zones of high and low accumulation of essential macro nutrients within the farmlands. Landmark University farmland indicated higher soil salinity than Covenant University farm land. Soil temperature (ST) data at Covenant University farm ranged from 296 - 314 K, while ST at Landmark University farm ranged from 289 - 317 K. Soil moisture content data for both farms ranged from 23 – 113 3 3 mmand 10 - 110 3 3 mmin Covenant and Landmark University farms, respectively. The sandy gravelly soil of Landmark University farm is suitable for the planting of root and tuber crops such as carrot, yam, potatoes, turmeric and beets. Cabbage, leafy vegetables and lemon grass can be grown successfully in Covenant University farm. The ecological risk assessment of toxic metals, showed that arsenic may present a moderate to very high biological risk to both plants and animals that feed on the soil of both farm lands. The site-specific information of the farm sites has been provided. This study provides database that can serve as useful guide in soil management decision making for better yiel

Evaluation of the impact of climate and human induced changes on the Nigerian forest using remote sensing

The majority of the impact of climate and human induced changes on forest are related to climate variability and deforestation. Similarly, changes in forest phenology due to climate variability and deforestation has been recognized as being among the most important early indicators of the impact of environmental change on forest ecosystem functioning. Comprehensive data on baseline forest cover changes including deforestation is required to provide background information needed for governments to make decision on Reducing Emissions from Deforestation and Forest Degradation (REED). Despite the fact that Nigeria ranks among the countries with highest deforestation rates based on Food and Agricultural Organization estimates, only a few studies have aimed at mapping forest cover changes at country scales. However, recent attempts to map baseline forest cover and deforestation in Nigeria has been based on global scale remote sensing techniques which do not confirm with ground based observations at country level. The aim of this study is two-fold: firstly, baseline forest cover was estimated using an ‘adaptive’ remote sensing model that classified forest cover with high accuracies at country level for the savanna and rainforest zones. The first part of this study also compared the potentials of different MODIS data in detecting forest cover changes at regional (cluster level) scale. The second part of this study explores the trends and response of forest phenology to rainfall across four forest clusters from 2002 to 2012 using vegetation index data from the MODIS and rainfall data obtained from the TRMM.Tertiary Education Trust Fund, Nigeri