John K. Maingi

A Landscape Approach for Detecting and Evaluating Change in a Semi-Arid Environment

Vegetation change in the American West has been a subject of concern throughout the twentieth century. Although many of the changes have been recorded qualitatively through the use of comparative photography and historical reports, little quantitative information has been available on the regional or watershed scale. It is currently possible to measure change over large areas and determine trends in ecological and hydrological condition using advanced space-based technologies. Specifically, this process is being tested in a community-based watershed in southeast Arizona and northeast Sonora, Mexico using a system of landscape pattern measurements derived from satellite remote sensing, spatial statistics, process modeling, and geographic information systems technology. These technologies provide the basis for developing landscape composition and pattern indicators as sensitive measures of large-scale environmental change and thus may provide an effective and economical method for evaluating watershed condition related to disturbance from human and natural stresses. The project utilizes the database from the North American Landscape Characterization (NALC) project which incorporates triplicate Landsat Multi-Spectral Scanner (MSS) imagery from the early 1970s, mid 1980s, and the 1990s. Landscape composition and pattern metrics have been generated from digital land cover maps derived from the NALC images and compared across a nearly 20-year period. Results about changes in land cover for the study period indicate that extensive, highly connected grassland and desertscrub areas are the most vulnerable ecosystems to fragmentation and actual loss due to encroachment of xerophytic mesquite woodland. In the study period, grasslands and desertscrub not only decreased in extent but also became more fragmented. That is, the number of grassland and desertscrub patches increased and their average patch sizes decreased. In stark contrast, the mesquite woodland patches increased in size, number, and connectivity. These changes have important impact for the hydrology of the region, since the energy and water balance characteristics for these cover types are significantly different. The process demonstrates a simple procedure to document changes and determine ecosystem vulnerabilities through the use of change detection and indicator development, especially in regard to traditional degradation processes that have occurred throughout the western rangelands involving changes of vegetative cover and acceleration of water and wind erosion.

Factors influencing wildfire occurrence and distribution in eastern Kentucky, USA

Most wildfires in Kentucky occur in the heavily forested Appalachian counties in the eastern portion of the state. In the present study, we reconstructed a brief fire history of eastern Kentucky using Landsat Thematic Mapper and Enhanced Thematic Mapper Plus images acquired between 1985 and 2002. We then examined relationships between fire occurrence and area burned, and abiotic and human factors. Abiotic factors included Palmer Drought Severity Index, slope, aspect, and elevation, and human factors included county unemployment rates, distance to roads, and distance to populated places. Approximately 83% of the total burned area burned only once, 14% twice, and 3% thrice. More fires burned in the winter compared with the fall, but the latter fires were larger on average and accounted for ~71% of the total area burned. Fire size was negatively correlated with Palmer Drought Severity Index for certain times of the year. There were significant relationships between elevation and slope and fire occurrence, but not between aspect and fire occurrence. We found links between fire location and proximity to roads and settlements, but we found no correlations between monthly unemployment rates and arson-caused fires.

Spatiotemporal patterns of elephant poaching in south-eastern Kenya

Abstract Context. Poaching of the African elephant for ivory had been on the increase since 1997 when the Convention on International Trade in Endangered Species (CITES) allowed a one-off legal sale of ivory by several southern Africa countries. In Kenya, reports indicate continuous year-to-year increase in elephant poaching since 2003. Aims. The goals of the study were to describe the temporal and spatial patterns of elephant poaching in south-eastern Kenya between 1990 and 2009, and examine relationships between observed patterns of poaching, and human and biophysical variables. The study aimed to answer the following questions: (1) how has elephant poaching varied seasonally and annually; (2) what are the spatial patterns of elephant poaching in the Tsavo Conservation Area (TCA); and (3) what are the relationships between observed patterns of poaching and human and biophysical variables? Methods. The study used elephant-poaching data and various GIS-data layers representing human and environmental variables to describe the spatial and temporal patterns of elephant poaching. The observed patterns were then related to environmental and anthropogenic variables using correlation and regression analyses. Key results. Elephant poaching was clustered, with a majority of the poaching occurring in the dry season. Hotspots of poaching were identified in areas with higher densities of roads, waterholes, rivers and streams. The Tsavo East National Park and the Tsavo National Park accounted for 53.7% and 44.8% of all poached elephants, respectively. The best predictors for elephant poaching were density of elephants, condition of vegetation, proximity to ranger bases and outposts, and densities of roads and rivers. Conclusions. Predictor variables used in the study explained 61.5–78% of the total variability observed in elephant poaching. The location of the hotspots suggests that human–wildlife conflicts in the area may be contributing to poaching and that factors that quantify community attitudes towards elephant conservation may provide additional explanation for observed poaching patterns. Implications. The poaching hotpots identified can be a used as starting point by the Kenya Wildlife Service (KWS) to begin implementing measures that ensure local-community support for conservation, whereas on other hotspots, it will be necessary to beef-up anti-poaching activities. There is a need for Kenya to legislate new anti-poaching laws that are a much more effective deterrence to poaching than currently exist.

Assessment of environmental impacts of river basin development on the riverine forests of eastern Kenya using multi-temporal satellite data

The utility of Landsat MSS (Multispectral Scanner) and SPOT XS data in monitoring the impacts of river basin development on a riverine forest located in the lower Tana River Basin of eastern Kenya was evaluated. Land cover change maps derived from Landsat MSS indicated little change in total forest area between 1975 and 1984. Land cover change maps derived from SPOT XS data indicated a 27% decline in forest area between 1989 and 1996. Mean patch size and area-perimeter ratio of the closed riverine forest remained virtually unchanged whereas these parameters for the open forest class decreased by 31% and 4% respectively. In addition, the average extent of the open riverine forest from the river channel declined by about 200 m between 1989 and 1996. This decline was attributed to decreased extent of floods along the floodplain following construction of dams in the upper river basin, and increased exploitation of the forests for fuelwood, especially in the vicinity of the established Bura Irrigation and Settlement Project. The greater lateral movement observed in the location of the river channel for the 1975-1985 period, compared to the 1985-1996 period, was also attributed to construction of dams in the upper river basin.

Growth rings in tree species from the Tana river floodplain, Kenya

ABSTRACT Growth rings of 19 tree species obtained from the Tana riverine forests in Kenya were studied for potential usefulness in dendrochronology. Among the growth ring characteristics used to qualitatively evaluate the potential usefulness of each species for dendrochronology included: distinctiveness of ring boundaries, ring circuit uniformity, ring wedging and ring sensitivity. Five species were identified as having the most desirable growth ring characteristics and therefore presented the best opportunity to crossdate ring width series among different trees. Crossdating among different trees would lead to the development of tree ring chronologies. These species included Acacia elatior, Acacia robusta, Tamarindus indica and Newtonia hildebrandtii, common on inactive levees occurring toward the edge of the floodplain, and Rinorea elliptica, an understory species found on levees. The timing of growth ring formation and exogenous factors responsible for its formation are yet to be identified. Drought conditions during the low river flow months of August and September are thought responsible for initiation of ring formation as these species grow in a semi-arid region and are thus entirely dependent on ground water.

Mapping Fire Scars in a Mixed‐Oak Forest in Eastern Kentucky, USA, Using Landsat ETM+ Data

Abstract Satellite images have been used successfully to map fire scars in a variety of ecosystems, but to date there are no documented studies on the application of this technology in the oak‐dominated deciduous forests of the eastern United States. The goal of the current study was to develop an approach suitable for mapping fire scars in eastern Kentucky using a single‐date Landsat ETM+ image. No single spectral band or spectral vegetation index appears successful in mapping fire scars in senesced oak‐dominated hardwood forests. Results obtained in this study suggest that a combination of Landsat spectral bands, particularly ETM+ 3, ETM+ 4, and ETM+ 7, are necessary for separating burned areas from low‐reflectance targets such as water bodies and shadows areas, and other land cover types such as senesced forests, and clear‐cut/strip mine surfaces. Of the techniques evaluated, the unstandardized principal components analysis (UPCA) resulted in the highest overall classification accuracy (85.3%) while KT brightness, greenness, and wetness resulted in the lowest overall fire scar classification accuracy (69.9%).

Mapping insect-induced pine mortality in the Daniel Boone National Forest, Kentucky using Landsat TM and ETM+ data

A decision tree classifier was used to create a three-species conifer map of the Daniel Boone National Forest, Kentucky using Landsat TM images and ancillary data. The resulting map had an overall classification accuracy of approximately 82%. In the second part of the study, Landsat TM and ETM+ images acquired in 1995 and 2002, respectively, were used to evaluate five change-detection techniques for mapping conifer damage caused by southern pine beetle (SPB). PCA and SARVI2 change-detection techniques resulted in the highest classification accuracies. Over 60% of the conifer species were killed as a result of SPB infestation.

BIOGEOGRAPHIC PATTERNS OF FOREST DIVERSITY AT MOUNT KASIGAU, KENYA

ABSTRACT Mount Kasigau, the most northeastern mountain in the Eastern Arc, rises steeply from arid plains to a moist summit at 1641 m. This paper examines the diversity contributions of this afromontane setting by compiling a chorological analysis of tree species richness, measuring ecological differences among forest community types, and interpreting physical-environmental and human-historical factors that influence diversity patterns. Between 2002 and 2006, stem densities and basal areas of woody plants > 10 cm dbh were measured in 55 (0.1 ha) plots placed at different elevations. The study reports 140 species, 46 were measured in only one plot, and affinities for 75 species to the Somalia-Masai (43%), Afromontane (29%), and Zanzibar-Inhambane (Coastal, 28%) floristic regions. Cluster and Indicator Species Analyses identified eight community types. Mount Kasigau uniquely conserves much forest cover and a diversity of woody plant species below evergreen forest at 1000 m. Ordination, using Nonmetric Multidimensional Scaling (NMDS), resulted in a three-dimensional solution that explained 47.9% of the variation among plots. Axis 2 showed the strongest relationship with elevation (R2= 0.523), but lower montane community types also vary by slope form, slope aspect, and past human activities. We show how this biogeographical analysis of diversity patterns at Mount Kasigau can guide local management and support important opportunities for montane forest conservation in East Africa.

Producing an urban system for the spatial development of Ghana: lessons for sub-Saharan Africa

This paper illustrates the power of geography in solving spatial problems. We demonstrate how an urban system can be produced to meet spatial development objectives stated in Ghana’s nascent National Urban Policy. Even though the growth pole, functional, territorial and economy of affection approaches have been used to theorize the role of towns, we conceptualize the role of towns in the development process as arenas for providing services, infrastructure, livelihoods, housing, governance and environmental protection. Urban systems are therefore produced to meet development objectives which are often spelled out in development plans or societal imperatives. Based on our conceptualization of the role of towns, we identify the current functional structure of Ghana’s urban system. This is followed by a determination of functional gaps and weaknesses in the country’s urban system. We offer ways of filling the gaps and strengthening weaknesses in the country’s urban system in the light of objectives of the proposed NUP. We conclude the paper with general lessons for sub-Saharan African countries.

Embedded histories and biogeographic interpretations of forest diversity at Mt. Kasigau, Kenya

Abstract Forest resources conserved at Mt. Kasigau, an Eastern Arc peak in southeastern Kenya, show a complex legacy of unique cultural adaptations influenced by profound effects from outside interventions. We compiled place-name maps, landscape narratives, and semi-structured interviews (2002–2015) to spatially interpret a dynamic history of biogeographical change since early settlement by the Kasigau Taita, influenced by regional trade networks, colonial ‘war-time’ authority, export markets, conservation enterprises, and a persistently growing need for incomes to offset livelihood insecurity. Adaptive co-management, if empowered through local participation, needs to better recognize and account for extra-local influences on livelihood strategies and their ecological effects.