Senior Lecturer, Kaduna State University
Evaluating Land Use Dynamics over Time
Land use change is a common feature of economic development all over the World. Most of this change is concentrated in locations where concern for ecological footprint and sustainable livelihood is very high. Available evidences showed that the World communities are at brink of major land use change and the land use change professionals and policy makers are uncertain about the direction and implications of these changes on the people and the environment. Therefore, an assessment of the global land use change will give an insight into the trend, driving factors and the implications land use change will have on food security biodiversity loss and climatic change such that a policy reversal that will maintain balance between socio – economic and ecological development may be advocated and implemented.
Recently, studies of agricultural land use dynamics are becoming important in order to assess the potential for agricultural land expansion and to make relevant information available to the local communities, investors and the government on locations where investments will bring higher returns and to steer investors away from fragile or marginal lands where agricultural investments could have adverse economic and or environmental implications. Information on productive capacity of land would help in appreciating alternative options for land use planning, assessing environmental impacts of land use and evaluating resilience and vulnerability of land use under different scenarios. Thus, my research activities involve assessment of trend, identification of drivers and hotspots of future land use change and projection of the implications of land use dynamics for food security, biodiversity loss and climatic change in major economies of the World with the use of spatially explicit datasets.
Abstract: Abstract Understanding factors that drive urban growth is essential to cellular automata (CA) based urban modeling. Multicollinearity among correlated factors may cause negative effects when building CA transition rules, leading to a decrease in simulation accuracy. We use a nonparametric generalized additive model (GAM) to evaluate these relationships through flexible smooth functions to capture the dynamics of urban growth. A GAM-based CA (termed GAM-CA) model was then developed to simulate the rapid urban growth in Shanghai, China from 2000 to 2015. GAM highlights the significance of each candidate factor driving urban growth during the past 15 years. Compared to logistic regression, the GAM-CA transition rules fitted the observed data better and yielded improved overall accuracy and hence more realistic urban growth patterns. The new CA model has great potential for capturing key driving factors to simulate dynamic urban growth, and can predict future scenarios under various spatial constraints and conditions.
Pub.: 20 Jul '17, Pinned: 12 Aug '17
Abstract: Neotropical cloud forests are a critically endangered ecosystem characterised by their unusual hydrological conditions which frequently make them important sources of clean potable water. To facilitate any meaningful research on cloud forest streams it is necessary to first describe the structure and composition of the local lotic aquatic communities and to establish which environmental factors structure them under natural conditions. The present study sampled the macroinvertebrate communities of rivers draining the montane cloud forests of Cucuso National Park in Honduras, where increasing anthropogenic pressures are threatening water quality. Using multivariate techniques a bottom-up approach was adopted to establish groups of similar sites and identify environmental factors driving the differences between these. Three site groupings emerged based largely on differences in taxon composition driven mainly by pH and altitude.Neotropical cloud forests are a critically endangered ecosystem characterised by their unusual hydrological conditions which frequently make them important sources of clean potable water. To facilitate any meaningful research on cloud forest streams it is necessary to first describe the structure and composition of the local lotic aquatic communities and to establish which environmental factors structure them under natural conditions. The present study sampled the macroinvertebrate communities of rivers draining the montane cloud forests of Cucuso National Park in Honduras, where increasing anthropogenic pressures are threatening water quality. Using multivariate techniques a bottom-up approach was adopted to establish groups of similar sites and identify environmental factors driving the differences between these. Three site groupings emerged based largely on differences in taxon composition driven mainly by pH and altitude.
Pub.: 02 Nov '16, Pinned: 12 Aug '17
Abstract: Prevention and control of wildlife disease invasions relies on the ability to predict spatio-temporal dynamics and understand the role of factors driving spread rates, such as seasonality and transmission distance. Passive disease surveillance (i.e., case reports by public) is a common method of monitoring emergence of wildlife diseases, but can be challenging to interpret due to spatial biases and limitations in data quantity and quality.We obtained passive rabies surveillance data from dead striped skunks (Mephitis mephitis) in an epizootic in northern Colorado, USA. We developed a dynamic patch-occupancy model which predicts spatio-temporal spreading while accounting for heterogeneous sampling. We estimated the distance travelled per transmission event, direction of invasion, rate of spatial spread, and effects of infection density and season. We also estimated mean transmission distance and rates of spatial spread using a phylogeographic approach on a subsample of viral sequences from the same epizootic. Both the occupancy and phylogeographic approaches predicted similar rates of spatio-temporal spread. Estimated mean transmission distances were 2.3 km (95% Highest Posterior Density (HPD95): 0.02, 11.9; phylogeographic) and 3.9 km (95% credible intervals (CI95): 1.4, 11.3; occupancy). Estimated rates of spatial spread in km/year were: 29.8 (HPD95: 20.8, 39.8; phylogeographic, branch velocity, homogenous model), 22.6 (HPD95: 15.3, 29.7; phylogeographic, diffusion rate, homogenous model) and 21.1 (CI95: 16.7, 25.5; occupancy). Initial colonization probability was twice as high in spring relative to fall.Skunk-to-skunk transmission was primarily local (< 4 km) suggesting that if interventions were needed, they could be applied at the wave front. Slower viral invasions of skunk rabies in western USA compared to a similar epizootic in raccoons in the eastern USA implies host species or landscape factors underlie the dynamics of rabies invasions. Our framework provides a straightforward method for estimating rates of spatial spread of wildlife diseases.
Pub.: 02 Aug '17, Pinned: 12 Aug '17
Abstract: We quantify tree dynamics over a century of free development in a small broad-leaved forest dominated by Fraxinus excelsior and Ulmus glabra. What are the internal and external factors driving the changes, and how predictable are they? What were the time scale and effects of the spread of Dutch elm disease (DED)?Vårdsätra, eastern central Sweden.The survival, growth and recruitment of all trees (≥12 cm girth) were monitored in 1912, 1967, 1988 and 2013 (more often for a part of the forest). Woody species in the field and shrub layers were surveyed in permanent plots in 1976 and 2012. We used transition matrix models to project changes in population sizes and species composition within the century and for 2050.The results indicate that the forest was in a successional development during the first period. The species composition had stabilized by 1967, except for an expansion of Acer platanoides and the drastic effect of DED that struck the forest around 2000. It took only a decade to kill virtually all large elms in the forest, leading to strong decrease in stem density and basal area. The evidence for effects of DED is still weak, but there has been an increase in saplings, notably of Fraxinus, Prunus padus, Ulmus, and of shoots of Corylus avellana. Several species that are abundant in the vicinity and as seeds fail to establish (Picea abies, Betula spp., Quercus robur, Populus tremula). Projections for 2050 based on the third period (1988–2013) are probably unrealistic since Fraxinus may also disappear because of the recent arrival of ash dieback.Slow dynamics in forests that could follow from climate change will locally probably be overruled by unforeseen catastrophes, such as invasions of forest pathogens. These initiate changes with long lag phases that are difficult to quantify. Still, a dense deciduous forest can resist invasion of colonist species and of regionally dominant conifers; the reason being unfavourable conditions for establishment rather than dispersal limitation.
Pub.: 14 Jul '17, Pinned: 29 Jul '17
Abstract: Understanding the response of plant species to soil factors on coastal sand dunes is critical for effective conservation of coastal habitats in the Mediterranean basin. Our main objectives were to investigate: i) the main soil factors driving species composition in a Mediterranean coastal dune environment; ii) the ecological requirements of focal plant species with respect to single soil factors; iii) whether the focal species of a given macrohabitat (including EU habitats) have similar edaphic needs. We identified 108 plots with three macrohabitats as strata (embryo dunes; mobile dunes; fixed dunes) by random stratified sampling design along the Tyrrhenian coast of central Italy in areas with a high degree of biodiversity and naturalness. Vegetation and soil data were collected in the plots.
Pub.: 08 Jun '17, Pinned: 29 Jul '17
Abstract: The differential response of marine populations to climate change remains poorly understood. Here, we combine common garden thermotolerance experiments in aquaria and population genetics to disentangle the factors driving the population response to thermal stress in a temperate habitat-forming species: the octocoral Paramuricea clavata. Using eight populations separated from tens of meters to hundreds of kilometers, which were differentially impacted by recent mortality events, we identify 25 °C as a critical thermal threshold. After one week of exposure at this temperature, seven of the eight populations were affected by tissue necrosis and after 30 days of exposure at this temperature, the mean % of affected colonies increased gradually from 3 to 97%. We then demonstrate the weak relation between the observed differential phenotypic responses and the local temperature regimes experienced by each population. A significant correlation was observed between these responses and the extent of genetic drift impacting each population. Local adaptation may thus be hindered by genetic drift, which seems to be the main driver of the differential response. Accordingly, conservation measures should promote connectivity and control density erosion in order to limit the impact of genetic drift on marine populations facing climate change.
Pub.: 13 Jul '17, Pinned: 29 Jul '17
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