Chukwudi Nwaogu

Is Nigeria losing its natural vegetation and landscape? Assessing the landuse-landcover change trajectories and effects in Onitsha using remote sensing and GIS

Abstract Onitsha is one of the largest commercial cities in Africa with its population growth rate increasing arithmetically for the past two decades. This situation has direct and indirect effects on the natural resources including vegetation and water. The study aimed at assessing land use-land cover (LULC) change and its effects on the vegetation and landscape from 1987 to 2015 using geoinformatics. Supervised and unsupervised classifications including maximum likelihood algorithm were performed using ENVI 4.7 and ArcGIS 10.1 versions. The LULC was classified into 7 classes: built-up areas (settlement), waterbody, thick vegetation, light vegetation, riparian vegetation, sand deposit (bare soil) and floodplain. The result revealed that all the three vegetation types decreased in areas throughout the study period while, settlement, sand deposit and floodplain areas have remarkable increase of about 100% in 2015 when compared with the total in 1987. Number of dominant plant species decreased continuously during the study. The overall classification accuracies in 1987, 2002 and 2015 was 90.7%, 92.9% and 95.5% respectively. The overall kappa coefficient of the image classification for 1987, 2002 and 2015 was 0.98, 0.93 and 0.96 respectively. In general, the average classification was above 90%, a proof that the classification was reliable and acceptable.

Soil organic carbon and total nitrogen stocks as affected by different land use in an Ultisol in Imo Watershed, southern Nigeria

ABSTRACT Soil organic carbon (SOC) and soil total nitrogen (STN) concentrations and stocks are essential for improving soil quality and increasing C-reservoir. The study aimed at quantifying the dynamics of soil properties under different land use in Imo watershed where there is no knowledge about the effects of land use on SOC and STN pool. Six land use: arable land (AL), forest land (FL), grassland (GL), shrubland hills (SL), urban built-up green (UL), and freshwater swamp-mangrove wetland (WL) were classified using ArcGIS 10.1 and FAO land use classification system. Soil samples were collected and analyzed from each land use under different soil depths and slope positions with three replications. Topsoil layer (0–30 cm) contributed to more than 90% of the total soil nutrients. Land use significantly affected SOC content, STN content, and bulk density. SOC and STN concentrations were in the order of FL > WL > GL > SL > UL > AL which revealed the potentials of FL and WL for SOC and STN sequestration. The study provides land users with the information to improve soil quality, conserve C and N stocks for ecological sustainability and climate change mitigation.

Land Use—Land Cover Change and Soil-Gully Erosion Relationships: A Study of Nanka, South-Eastern Nigeria Using Geoinformatics

This study aimed at identifying the land use-land cover (LULC) types and their changes by mapping the soil erodibility intensity, and estimating the LULC change caused by soil-gully erosion in Nanka region using geoinformatics tools. Data covering 1991, 2003 and 2015 were acquired from the Global Land Cover Facility (GLCF)-an Earth Science Data Interface, and from the National Space Research and Development Agency, Abuja (NASRDA). In addition, land use-land cover (LULC) data of Nanka and its environs were generated from the local government boundary map and Nigerian Administrative map at 1: 50,000 topographic scale. ENVI (version 4.7), ArcGIS 10.1, the RUSLE model and statistica software packages were used to process and analyse the data. The results revealed that areas with steep slopes have high and severe erosion levels except for Isuofia community which is on steep slope yet, has slight erosion because of the prevalence of dense forest vegetation cover. Integration of Remote Sensing, GIS and the RUSLE model has shown technical benefit, cost-effectiveness with reliable result and should be applied in the future assessment of erosion in Nigeria and other African countries.

Prediction Models for Landscape Development in GIS

Ameliorating the impacts of global change on the physical and socioeconomic environment is essential for the restoration and sustainability of our ecosystems. Landscape modifications have been discovered as one of the primary causes of the environmental change and has therefore gained reasonable attention in the modeling techniques, because understanding the land use-land cover change (LULCC), the drivers and processes provides the solution to the environmental challenge. Sequel to this, several empirical methods and software for modeling LULCC have been developed and applied such as the spatial-statistical based (regressions, Artificial Neural Networks, GISCAME), Markov Chain, Cellular automata, the hybrid (CA-Markov), Agent-Based, CLUE, Land Change Modeler (LCM), Dinamica EGO, GEOMOD, and Scenarios for InVEST. This paper reviews the implementations, prospects, and the limits of these modeling software packages. Comparative assessment review of the models including their capabilities, applications and output were also highlighted. Finally, two of the models (LCM and CLUE) were used to predict the LULCC in a municipal area in south-east, Nigeria (a case study), and this helps to illustrate the afore-mentioned explanations and variations about the outputs of different models in assessing the LULCC of same location in time. Different models can behave differently when applied in same location at the same time as demonstrated by the applications of LCM and CLUE in our study. In addition to other LULC type dynamics in the models outputs, we have prediction map from CLUE showing higher built-up areas (42.7 km2) compared with that of LCM result (35.2 km2) while, the LCM projection revealed more areas for light vegetation cover (29.5 km2) in comparison with the 16.5 km2 from the CLUE model result.

Assessment of the impacts of municipal solid waste dumps on soils and plants

ABSTRACT The study aimed at evaluating the impacts of open municipal solid wastes dumps on soil and vegetation near the main roads linking major cities in Nigeria. We hypothesised that the metals from the wastes exerted substantial impacts at the dump sites which affect the soil and plants. Data were analysed from five dump sites and five control sites. The result revealed that the effects of the heavy metals (HM) were significant and higher at the dump sites where their concentrations were far above the EU, and Canadian environmental quality permissible limits for agricultural soils and vegetation. In contrast with dump sites, a significant relationship (R2 = 0.70; p < .001) was found between the number of plant species and area at control sites. Shrubs and herbs were more tolerance with higher contents of HM compared with grasses. Plants leaves showed more HM contents compared to the shoots or roots. The soil and plants contents of the HM were relatively in the order of Zn > Cr > Pb at both dump sites and control sites. Further study on the effects of more HM on soil and plant is recommended in the area. Recycling and bio-phytoremediation processes should also be introduced.

Evaluating Some Aspects of Gas Geochemistry of some North Sea Oil Fields

Gas geochemistry, an integral part of petroleum geosciences, has been used for evaluating source rocks potential for shale gas and in conventional exploration as a guide for determining potential productive formations. However, in contemporary times, new concepts of gas geochemistry have been applied in delineating the effectiveness of caprocks. Caprock is a vital element of a petroleum system, the volumes of rocks overlaying reservoirs are responsible for the configuration on which the accumulation sits and fosters essential preservation. In this study headspace gas served the purpose of delineating leakage and determining migration pathways, mechanism and discriminating gas types in the formations overlaying the reservoirs.