Genesis T. Yengoh

Anthropogenic sources and environmentally relevant concentrations of heavy metals in surface water of a mining district in Ghana: a multivariate statistical approach

The levels of heavy metals in surface water and their potential origin (natural and anthropogenic) were respectively determined and analysed for the Obuasi mining area in Ghana. Using Hawths tool an extension in ArcGIS 9.2 software, a total of 48 water sample points in Obuasi and its environs were randomly selected for study. The magnitude of As, Cu, Mn, Fe, Pb, Hg, Zn and Cd in surface water from the sampling sites were measured by flame Atomic Absorption Spectrophotometry (AAS). Water quality parameters including conductivity, pH, total dissolved solids and turbidity were also evaluated. Principal component analysis and cluster analysis, coupled with correlation coefficient analysis, were used to identify possible sources of these heavy metals. Pearson correlation coefficients among total metal concentrations and selected water properties showed a number of strong associations. The results indicate that apart from tap water, surface water in Obuasi has elevated heavy metal concentrations, especially Hg, Pb, As, Cu and Cd, which are above the Ghana Environmental Protection Agency (GEPA) and World Health Organisation (WHO) permissible levels; clearly demonstrating anthropogenic impact. The mean heavy metal concentrations in surface water divided by the corresponding background values of surface water in Obuasi decrease in the order of Cd > Cu > As > Pb > Hg > Zn > Mn > Fe. The results also showed that Cu, Mn, Cd and Fe are largely responsible for the variations in the data, explaining 72% of total variance; while Pb, As and Hg explain only 18.7% of total variance. Three main sources of these heavy metals were identified. As originates from nature (oxidation of sulphide minerals particularly arsenopyrite-FeAsS). Pb derives from water carrying drainage from towns and mine machinery maintenance yards. Cd, Zn, Fe and Mn mainly emanate from industry sources. Hg mainly originates from artisanal small-scale mining. It cannot be said that the difference in concentration of heavy metals might be attributed to difference in proximity to mining-related activities because this is inconsistent with the cluster analysis. Based on cluster analysis SN32, SN42 and SN43 all belong to group one and are spatially similar. But the maximum Cu concentration was found in SN32 while the minimum Cu concentration was found in SN42 and SN43.

Crop Yield Gaps in Cameroon

Although food crop yields per hectare have generally been increasing in Cameroon since 1961, the food price crisis of 2008 and the ensuing social unrest and fatalities raised concerns about the country’s ability to meet the food needs of its population. This study examines the country’s potential for increasing crop yields and food production to meet this food security challenge. Fuzzy set theory is used to develop a biophysical spatial suitability model for different crops, which in turn is employed to ascertain whether crop production is carried out in biophysically suited areas. We use linear regression to examine the trend of yield development over the last half century. On the basis of yield data from experimental stations and farmers’ fields we assess the yield gap for major food crops. We find that yields have generally been increasing over the last half century and that agricultural policies can have significant effects on them. To a large extent, food crops are cultivated in areas that are biophysically suited for their cultivation, meaning that the yield gap is not a problem of biophysical suitability. Notwithstanding, there are significantly large yield gaps between actual yields on farmers’ farms and maximum attainable yields from research stations. We conclude that agronomy and policies are likely to be the reasons for these large yield gaps. A key challenge to be addressed in closing the yield gaps is that of replenishing and properly managing soil nutrients.

Determinants of yield differences in small-scale food crop farming systems in Cameroon

BackgroundIn sub-Saharan Africa, small-scale farmers make up the majority of food producers. While recognizing that the yields per hectare for main food crops are generally low in small-scale food production systems in this region, there are considerable differences in yield output among individual farmers. At the very local scale, why do these differences exist? By examining factors that are associated with yield differences, policy can be better informed and tailored to respond to challenges of food production among this important group of producers.ResultsWhen the influence of biophysical factors is controlled by sampling farmers within the same environment, the analysis distinguishes three clusters of factors with which food crop yield differences can be associated: the input, management and socio-cultural clusters. In the input cluster, the use of basic inputs such as animal droppings and improved seeds do significantly improve yields. However, there are constraints at farm and household levels that may have to be overcome to optimize the availability and use of these inputs. In the farm management cluster, the method of residue management and the control of pests and crop diseases are important in determining yield differences. Issues of gender rights and access to agricultural production resources dominate socio-cultural clusters.ConclusionsSmall investments that are properly targeted to improve basic techniques of farming can make an appreciable difference in food crop yields and food security at the local level. While directed investments in services such as extension may contribute significantly to propagate the use of some technologies (composting, residue management, manure use), cost constraints limit the propagation of other technologies (advanced seed development and improvement, production of inorganic fertilizers) to higher levels of food governance systems. Women form an important population among small-scale farmers and play an indispensable role in food production. Addressing constraints to their access to food production resources (physical, financial, cultural, legal) would be a vital step towards sustainably improving food production. Present food demand trends in sub-Saharan Africa offer an opportunity through which many small-holder farming communities can be drawn out of poverty if some local-level challenges to yield improvement can be overcome.

Agro-climatic resources and challenges to food production in Cameroon

The agro-climatic resources of Cameroon are examined in light of the potential for food crop production and challenges presented by climate change. We find that the diversity of Cameroons agro-climate offers the potential for the cultivation of a variety of food crops. This feature of Cameroonian agriculture can be used in addressing the countrys adaptive capacity to climate change. However, the Savanna zones of the country, which are its most productive, are also the most vulnerable to climate change. The main climate change challenge in these Savanna zones is that of drought and associated agricultural water demand. Appropriate management strategies to address agricultural water demand can also address important problems in Cameroonian agriculture, such as the effects of climatic uncertainties in small-scale food crop production and soil nutrient depletion. To ensure the success of these management strategies, a number of obstacles may have to be addressed.

Management of natural resources in a conflicting environment in Ghana: unmasking a messy policy problem

Resource use conflict is an enduring problem for science and policy making. Using in-depth interviews and focus group discussions with resource users, policy makers and key informants, we explored four case examples of resource use conflict within lands and forestry, fisheries, oil and the mining sectors in Ghana. Results indicate that resource use conflict consists of a complex, non-linear system of balancing and reinforcing feedback loops that recur across resource sectors. The conflicts are difficult to clearly define, have many interdependencies and are multi-causal. Specifically, dysfunctional policy, commoditisation of land, infringement on rights of users, shift from communal to private land ownership, renegotiation of rights, and unclear roles and responsibilities of government agencies, exacerbate conflicts among resource users, managers and policy makers in Ghana. In addition, supranational policy such as the protocol of the Economic Community of West African States, which promotes free movement of people and goods within the 16-nation community, is a driver of conflict between native farmers and nomadic Fulani herders. Clear policy directions from government that outlines the specific roles of various departments involved in resource issues together with a holistic community participatory approach is therefore required to comprehensively understand and address such conflicts.

Mapping of noise risk zones derived from religious activities and perceptions in residential neighbourhoods in the Cape Coast metropolis, Ghana

Ambient noise levels emanating from religious activities in residential neighbourhoods are an emerging environmental problem that educes little attention from enforcement agencies and policy makers in Ghana. This paper set out to quantify religious noise exposure in urban residential neighbourhoods in the Cape Coast metropolis of Ghana. Subjective annoyance levels of residents in selected communities were determined. Noise risk zones were mapped using ARCGIS 9.3 software and surface interpolation for the data was carried out using inverse distance weighting. The results show that most (77 and 86 per cent) of the locations recorded noise levels that were above the Ghana Environmental Protection Agency maximum permissible limit for day and night, respectively. Pearsons correlation coefficient for day and night noise exposure shows strong association (0.714) at the 0.01 level. There is variability in the levels of noise for both day and night, which are rather high (standard deviation = 7.59477 and 7.94022, respectively). Generally, levels of noise exposure correlated with levels of annoyance of residents, except that the highest noise exposure was not recorded in the community where the annoyance level of residents was highest. Residential neighbourhoods within the study area largely experienced safe to tolerable levels of religious noise, although 5 per cent were within the high-risk zone. Given that the selected residential areas have high population densities, even when the dispersion of noise risk is spatially limited, it affects a large number of people who belong to different socio-economic classes.

Floods in the Douala metropolis, Cameroon: attribution to changes in rainfall characteristics or planning failures?

With urban populations worldwide expected to witness substantial growth over the next decades, pressure on urban land and resources is projected to increase in response. For policy-makers to adequately meet the challenges brought about by changes in the dynamics of urban areas, it is important to clearly identify and communicate their causes. Floods in Douala (the most densely populated city in the central African sub-region), are being associated chiefly with changing rainfall patterns, resulting from climate change in major policy circles. We investigate this contention using statistical analysis of daily rainfall time-series data covering the period 1951–2008, and tools of geographic information systems. Using attributes such as rainfall anomalies, trends in the rainfall time series, daily rainfall maxima and rainfall intensity–duration–frequency, we find no explanation for the attribution of an increase in the occurrences and severity of floods to changing rainfall patterns. The culprit seems to be the massive increase in the population of Douala, in association with poor planning and investment in the citys infrastructure. These demographic changes and poor planning have occurred within a physical geography setting that is conducive for the inducement of floods. Failed urban planning in Cameroon since independence set the city up for a flood-prone land colonization. This today translates to a situation in which large portions of the citys surface area and the populations they harbor are vulnerable to the citys habitual annual floods. While climate change stands to render the city even more vulnerable to floods, there is no evidence that current floods can be attributed to the changes in patterns of rainfall being reported in policy and news domains.

Applications of NDVI for Land Degradation Assessment

In the late 1960s, several researchers began using red and near-infrared reflected light to study vegetation (Pearson and Miller 1972). In the late 1960s, ratios of red and near-infrared light were used to assess turf grass condition and tropical rain forest leaf area index (Birth and McVey 1968; Jordan 1969). Compton Tucker was the first to use it for determining total dry matter accumulation, first from hand-held instruments (Tucker 1979), and then from NOAA AVHRR satellite data (Tucker et al. 1981, 1985), demonstrating that the growing season integral of frequent NDVI measurements represented the summation of photosynthetic potential as total dry matter accumulation. Starting in July 1981, a continuous time series of global NDVI data at a spatial resolution of 8 km has been available from the AVHRR instrument mounted on NOAA weather satellites. Soon, researchers realized the value of NDVI time-series remote sensing (Goward et al. 1985; Justice et al. 1985; Townshend et al. 1985; Tucker et al. 1985). This early work was the spur for development of the higher-resolution Moderate-Resolution Imaging Spectroradiometer (MODIS) instrument. The application of satellite NDVI data has blossomed into many fields of natural resources investigation (see Annex 1). One particular appeal of remote sensing in the study of large geographic areas, or at multiple times over the year(s), is the potential for cost savings (Pettorelli 2013). We examine the use of NDVI in research on land-use and land-cover change, drought, desertification, soil erosion, vegetation fires, biodiversity monitoring and conservation, and soil organic carbon (SOC).

Key Issues in the Use of NDVI for Land Degradation Assessment

A substantial body of research has established the correlation between NDVI and aboveground biomass, and knowledge of the theoretical basis for using satellite-derived NDVI as a general proxy for vegetation conditions has advanced (Mbow et al. 2014; Pettorelli et al. 2005; Sellers et al. 1994). Reduction of primary productivity is a reliable indicator of the decrease or destruction of the biological productivity, particularly in drylands (Wessels et al. 2004; Li et al. 2004). NPP expressed in g of C m−2 years−1 and quantifies net carbon fixed by vegetation. According to Cao et al. (2003), NPP is “the beginning of the carbon biogeochemical cycle,” defined mathematically as in Eq. (5.1):