In sub-Saharan Africa, urban and peri-urban food production has been identified as an important resource for meeting the challenges of rapidly growing cities, and the positive aspects of such production have been well documented in the literature. This paper examines some of the health and environmental concerns associated with urban and peri-urban agriculture (UPA). Empirical evidence from the city of Kano in northern Nigeria suggests that there is currently much reason for concern as industrial and domestic toxins are reaching dangerously high levels. As soils and water channels become increasingly polluted, the sustainability of urban and peri-urban food production is questioned. Since the health implications of long-term exposure to toxins are unclear, it is suggested that coordinated longitudinal research involving urban planners, agricultural scientists and health specialists is urgently needed. In addition, it remains crucial that government and institutional actors effectively monitor and enforce both environmental and zoning by-laws, if the health and environmental constraints of UPA are to be overcome, and the future sustainability of production is to be assured.
In this work, the DRASTIC and GALDIT models were employed to determine the groundwater vulnerability to contamination from anthropogenic activities and seawater intrusion in Kapas Island. In addition, the work also utilized sensitivity analysis to evaluate the influence of each individual parameter used in developing the final models. Based on these effects and variation indices of the said parameters, new effective weights were determined and were used to create modified DRASTIC and GALDIT models. The final DRASTIC model classified the island into five vulnerability classes: no risk (110-140), low (140-160), moderate (160-180), high (180-200), and very high (>200), covering 4, 26, 59, 4, and 7 % of the island, respectively. Likewise, for seawater intrusion, the modified GALDIT model delineates the island into four vulnerability classes: very low (<90), low (90-110), moderate (110-130), and high (>130) covering 39, 33, 18, and 9 % of the island, respectively. Both models show that the areas that are likely to be affected by anthropogenic pollution and seawater intrusion are within the alluvial deposit at the western part of the island. Pearson correlation was used to verify the reliability of the two models in predicting their respective contaminants. The correlation matrix showed a good relationship between DRASTIC model and nitrate (r = 0.58). In a similar development, the correlation also reveals a very strong negative relationship between GALDIT model and seawater contaminant indicator (resistivity Ωm) values (r = -0.86) suggesting that the model predicts more than 86 % of seawater intrusion. In order to facilitate management strategy, suitable areas for artificial recharge were identified through modeling. The result suggested some areas within the alluvial deposit at the western part of the island as suitable for artificial recharge. This work can serve as a guide for a full vulnerability assessment to anthropogenic pollution and seawater intrusion in small islands and will help policy maker and manager with understanding needed to ensure sustainability of the island's aquifer.
Cities worldwide are experiencing rapid spatial growth and cities in the less developed countries are already accounting for more of this growth. If such rapid growth is unplanned and uncontrolled, it would have adverse effect on the environment and in most cases, vegetation is highly endangered. Such removal of vegetation cover causes great harm to the ecosystem and contributes greatly to the global warming effect. The aim of this paper is to analyze urban expansion and its impact on vegetation cover in Kaduna metropolis, Nigeria using geospatial techniques. Landsat MSS imagery of 1973, Landsat TM image obtained in 1990, Landsat ETM+ data of 2001 and Nigerian Sat-1 image (2009) were used. Visual interpretation method was used to sort the various datasets into land use/cover classes. The built-up area and vegetation cover were extracted and the rates of change were ascertained for each of the landcover types. ILWIS 3.3 software was used for the analysis. The results show that the built-up area increased from 14.3% in 1973 to 44.1% in 2009.
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