An Overview of the Implications of Global Change for Natural and Managed Terrestrial Ecosystems

Changes in vegetation cover and land use can cause the fragmentation and destruction of ecosystems, resulting in a negative impact on biological diversity. It is likely that it occurred in recent decades in the Selva “El Ocote” Biosphere Reserve, in Chiapas, Mexico. Therefore, the objective of this research project was to determine the rate of change in vegetation and land use for the southern zone of the Selva El Ocote Biosphere Reserve (REBISO) and its adjacent area, for the period 1980-2022. First, a characterization of the types of vegetation and land use was carried out in two polygons (areas) located to the south of REBISO based on Landsat images. Subsequently, a supervised classification was carried out, and finally the rate of change in land use and vegetation was determined based on the rate of change formula described by the FAO. The results obtained show that in the polygon called "General Lázaro Cárdenas", in its section located within the REBISO, it consisted of seven types of vegetation cover and land use, of which were Acahual, Selva Median Subperennifolia, Human Settlements, Roads, Pastures, River and Agricultural Zone; while in its section outside REBISO, six types of cover and land uses were identified: Acahuales, Human Settlements, Roads, Pastures, Medium Subevergreen Forest and Agricultural Zones. On the other hand, for the polygon called "Riviera Piedra Parada", in its section located within REBISO, it was characterized by seven types of vegetation cover and land use, which were: Acahuales, Human Settlements, Roads, Pastures, Low Jungle Deciduous, Water Bodies and Agricultural Zones; while, in its section located outside REBISO, nine types of vegetation cover and land uses were identified: Acahuales, Human Settlements, Roads, Bodies of Water, Sinkhole, Pastures, Low Deciduous Forest and Agricultural Zones. The rate of change in the section located within the REBISO of the "General Lázaro Cárdenas" polygon was characterized by the increase of Acahual, Pastizal and Agricultural Zones, and by the decrease of Selva Mediana from 1984 to 2022. The section of this polygon located outside the REBISO, it was characterized by a decrease in Medium Forest, as well as an increase in Grasslands, Acahual, Roads, Human Settlements and Agricultural Zones in the same period. As for the section located within the REBISO of the "Riviera Piedra Parada" polygon, the rate of change was characterized by the decrease in Low Deciduous Forest and an increase in Acahual, Bodies of water and agricultural areas in the same period, while that the section of this polygon located outside the REBISO, was characterized by the decrease of Acahual, Selva Baja Caducifolia from 1984 to 2022. This information suggests the loss of original plant associations and the increase of anthropogenic land uses inside and outside the REVIEW. This information is important to be able to carry out the update of its Management Plan, and allow the creation of different mechanisms that help the sustainable use of its natural resources, contributing to the conservation of its flora and fauna, and the improvement of quality of life of the communities in the area. Los cambios de cobertura vegetal y de uso de suelo pueden ocasionar la fragmentación y destrucción de ecosistemas, resultando en un impacto sobre la diversidad biológica. Es probable que haya ocurrido en las últimas décadas en la Reserva de la Biosfera Selva “El Ocote”, en Chiapas, México. Por ello, el objetivo de este proyecto de investigación fue determinar la tasa de cambio en la vegetación y uso de suelo para la zona sur de la Reserva de la Biosfera Selva El Ocote (REBISO) y su área adyacente, para el periodo 1984-2022. Primero se llevó a cabo una caracterización de los tipos de vegetación y uso de suelo en dos polígonos (áreas) localizados al sur de la REBISO a partir de imágenes Landsat. Posteriormente se realizó una clasificación supervisada, y finalmente se determinó la tasa de cambio de uso de suelo y vegetación a partir de la fórmula de tasa de cambio descrita por la FAO (1996). Los resultados obtenidos muestran que en el polígono denominado “General Lázaro Cárdenas”, en su sección ubicada dentro de la REBISO, constó de siete tipos de cobertura vegetal y uso de suelo, de los cuales fueron Acahual, Selva Mediana Subperennifolia, Asentamientos Humanos, Caminos, Pastizales, Río y Zona Agrícolas; mientras que en su sección fuera de la REBISO, se identificaron seis tipos de cobertura y usos de suelo: Acahuales, Asentamientos Humanos, Caminos, Pastizales, Selva Mediana Subperennifolia y Zonas Agrícolas. Por otro lado, para el polígono denominado “Riviera Piedra Parada”, en su sección ubicada dentro de la REBISO, se caracterizó por siete tipos de cobertura vegetal y uso de suelo los cuales fueron, Acahuales, Asentamientos Humanos, Caminos, Pastizales, Selva Baja Caducifolia, Cuerpos de Agua y Zonas Agrícolas; mientras que, en su sección ubicada fuera de la REBISO, se identificaron nueve tipos de cobertura vegetal y usos de suelo: Acahuales, Asentamientos Humanos, Caminos, Cuerpos de Agua, Dolina, Pastizales, Selva Baja Caducifolia y Zonas Agrícolas. La Tasa de cambio en la sección localizada dentro de la REBISO del polígono “General Lázaro Cárdenas” se caracterizó por el incremento de Acahual, Pastizal y Zonas Agrícolas, y por la disminución de Selva Mediana desde 1984 hasta el 2022. La sección de este polígono localizada fuera de la REBISO, se caracterizó por una disminución de Selva Mediana, así como por un aumento de Pastizal, Acahual, Caminos, Asentamientos Humanos y de Zonas Agrícolas en el mismo periodo. En cuanto a la sección localizada dentro de la REBISO del polígono “Riviera Piedra Parada”, la tasa de cambio se caracterizó por la disminución de Selva Baja Caducifolia y un aumento de Acahual, Cuerpos de agua y de Zonas agrícolas en el mismo periodo, mientras que la sección de este polígono localizada fuera de la REBISO, se caracterizó por la disminución de Acahual, Selva Baja Caducifolia de 1984 al 2022. Esta información sugiere la pérdida de asociaciones vegetales originales y el aumento de usos de suelo antropogénicos dentro y fuera de la REBISO. Esta información es importante para poder llevar a cabo la actualización de su Plan de Manejo, y permitir la creación de distintos mecanismos que ayuden al aprovechamiento sustentable de sus recursos naturales, contribuyendo a la conservación de su flora y fauna, y al mejoramiento de calidad de vida de las comunidades de la zona.

Bernardi, R. E., M. Buddeberg, M. Arim, and M. Holmgren. 2019. Forests expand as livestock pressure declines in subtropical South America. Ecology and Society 24(2):19. https://doi.org/10.5751/ES-10688-240219

Aerial images of the high summits of the Spanish Central Range reveal significant changes in vegetation over the period 1957 to 1991. These changes include the replacement of high-mountain grassland communities dominated by Festuca aragonensis, typical of the Cryoro-Mediterranean belt, by shrub patches of Juniperus communis ssp. alpina and Cytisus oromediterraneus from lower altitudes (Oro-Mediterranean belt). Climatic data indicate a shift towards warmer conditions in this mountainous region since the 1940s, with the shift being particularly marked from 1960. Changes include significantly higher minimum and maximum temperatures, fewer days with snow cover and a redistribution of monthly rainfall. Total yearly precipitation showed no significant variation. There were no marked changes in land use during the time frame considered, although there were minor changes in grazing species in the 19th century. It is hypothesized that the advance of woody species into higher altitudes is probably related to climate change, which could have acted in conjunction with discrete variations in landscape management. The pronounced changes observed in the plant communities of the area reflect the susceptibility of high-mountain Mediterranean species to environmental change.

Part 1 Patterns and determinants of climate and landscape change: scenarios of global warming, Stephen H. Schneider evaluating landscape change - patterns of worldwide deforestation and local fragmentation, Martha J. Groom and Nathan Schumaker population and community processes in the response of terrestrial ecosystems to global change, David S. Schimel. Part 2 Physiology and population responses to environmental change: terrestrial vegetation and climate change - integrating models and experiments, Stephen W. Pacala and George C. Hurtt plant defense, herbivory, and climate change, Matthew P. Ayres population responses to environmental change - operative environments, physiologically structured models, and population dynamics, Arthur E. Dunham climate change and ecological interactions, Anthony R. Ives and George Gilchrist individual-based models for predicting effects of global change, William W. Murdoch. Part 3 Evolutionary responses to environmental change: evolutionary genetics and climatic change - will animals adapt to global warming?, Ary A. Hoffmann and Mark W. Blows evolutionary responses of plants to global change, Monica A. Gever and Todd E. Dawson the evolutionary dynamics of fragmented plant populations, Kent S. Holsinger genetic consequences of extinction and recolonization in fragmented habitats, David E. McCauley evolution and extinction in response to environmental change, Michael Lynch and Russell Lande global change - lessons from and for evolutionary biology, Joseph Travis and Douglas J. Futuyma. Part 4 Community responses to environmental change: species dynamics and global environmental change - a perspective from ecosystem experiments, Stephen R. Carpenter, et al effects of global climate change on North American birds and their communities, Terry L. Root implications of climate change for stream communities, Nancy B. Grimm paleoecological perspectives on modeling broad-scale responses to global change, James S. Clark carbon dioxide limitation and potential direct effects of its accumulation on plant communities, David Tilman a salty and salutary perspective on global change, Robert T. Paine forecasting ecological responses to global change - the need for large-scale comparative studies, Michael L. Pace. Part 5 Landscape change and habitat fragmentation: species invasions and deletions - community effects and responses to climate and habitat change, David M. Lodge species diversity, spatial scale, and global change, Susan Harrison effects of global change on the dynamics of insect host-parasitoid interactions, M.P. Hassell, et al conservation planning for species occupying fragmented landscapes - the case of the Northern Spotted Owl, Kevin McKelvey, et al part contents.

Detecting vulnerability of humid tropical forests to multiple stressors

’s (2012) conclusion that observed climate change is comparableto projections, and in some cases exceeds projections, allows further inferences ifwe can quantify changing climate forcings and compare those with projections.The largest climate forcing is caused by well-mixed long-lived greenhouse gases.Here we illustrate trends of these gases and their climate forcings, and we discussimplications. We focus on quantities that are accurately measured, and we includecomparison with fixed scenarios, which helps reduce common misimpressionsabout how climate forcings are changing.Annual fossil fuel CO

Land management and land-use change can either release carbon (as CO{sub 2}) to the atmosphere, for example when forests are converted to agricultural lands, or withdraw carbon from the atmosphere as forests grow on cleared lands or as management practices sequester carbon in soil. The purpose of this work was to calculate the annual sources and sinks of carbon from changes in land use and management, globally and for nine world regions, over the period 1850 to 2000. The approach had three components. First, rates of land-use change were reconstructed from historical information on the areas of croplands, pastures, forests, and other lands and from data on wood harvests. In most regions, land-use change included the conversion of natural ecosystems to cultivated lands and pastures, including shifting cultivation, harvest of wood (for timber and fuel), and the establishment of tree plantations. In the U.S., woody encroachment and woodland thickening as a result of fire suppression were also included. Second, the amount of carbon per hectare in vegetation and soils and changes in that carbon as a result of land-use change were determined from data obtained in the ecological and forestry literature. These data on land-use change and carbon stocks weremore » then used in a bookkeeping model (third component) to calculate regional and global changes in terrestrial carbon. The results indicate that for the period 1850-2000 the net flux of carbon from changes in land use was 156 PgC. For comparison, emissions of carbon from combustion of fossil fuels were approximately 280 PgC during the same interval. Annual emissions from land-use change exceeded emissions from fossil fuels before about 1920. Somewhat more that half (60%) of the long-term flux was from the tropics. Average annual fluxes during the 1980s and 1990s were 2.0 and 2.2 ({+-}0.8) PgC yr{sup -1} (30-40% of fossil fuel emissions), respectively. In these decades, the global sources of carbon were almost entirely from the tropics. Outside the tropics, the average net flux of carbon attributable to land-use change and management decreased from a source of 0.06 PgC yr{sup -1} during the 1980s to a sink of 0.03 PgC yr{sup -1} during the 1990s. According to these analyses, changes in land use were responsible for sinks in North America and Europe and for small sources in other non-tropical regions.« less

Soil erosion, with the progressive loss of fertile topsoil and its negative impact on agricultural productivity, has become a critical global environmental problem. In the second half of the 20th century, many municipalities in Serbia experienced significant changes in land use, vegetation, and environmental conditions. The drive towards industrialization and urbanization aimed to improve the living standards of the population, but as a consequence, it led to substantial depopulation of rural areas and the adoption of inadequate agricultural practices, which, in turn, further intensified soil erosion. This study focuses on the Sokobanjska Moravica River basin (Eastern Serbia), extending to the Bovan Lake Dam and upstream, with a total area of 540.4 km². The basin is situated in a characteristic karst landscape. Changes in erosion intensity and runoff from this basin are analyzed using the Intensity of Erosion and Outflow (IntErO) model, which algorithmically integrates the widely used Erosion Potential Method (EPM) with innovative computational techniques to predict sediment production and runoff from the river basin accurately. This analysis utilizes GIS software and official statistical yearbook data, focusing on the period from the second half of the 20th century, including the analysis of the current state. According to our research, the most intensive changes in land use occurred between 1961 and 1971, marking the beginning of the period of a decline in rural population and, consequently, a decrease in erosion intensity. Key findings indicate that predominant changes in land use and vegetation led to a shift from crop farming to animal husbandry. After 1971, ongoing depopulation, particularly in rural areas, resulted in a gradual and steady decrease in erosion intensity. The primary aim of this study is to support policymakers in developing more effective soil and water conservation regulations. By making recommendations for the protection of vegetation, and thus the soil within this river basin, this research helps ensure their long-term preservation. Future research should focus on the long-term impacts of current land use practices and develop strategies to mitigate erosion in the context of changing climate conditions.

One of the greatest challenges in global‐change research is to predict the future distribution of vegetation. Most models of vegetation change predict either the response of a patch of present vegetation to climatic change or the future equilibrium distribution of vegetation based on the present relationship between climate and vegetation. Here we present a model that is, to our knowledge, the first model of ecosystem change in response to transient changes in climate, disturbance regime, and recruitment over the next 50‐500 yr. The frame‐based model uses quantitative and qualitative variables to develop scenarios of vegetation change from arctic tundra to boreal forest in response to global changes in climate (as predicted by general circulation models [GCMs]), fire, and land use. Seed availability, tree growth rate, and probability of fire were the model parameters that most strongly influenced the balance between tundra and boreal forest in transitional climates. The rate of climatic warming strongly affected the time lag between the onset of climate change and the simulated ecosystem response but had relatively little effect on the rate or pattern of ecosystem change. The model calculated that, with a gradual ramped change of 3°C in the next century (corresponding to average rate of warming predicted by GCMs), any change from tundra to forest would take 150 yr, consistent with pollen records. The model suggested that tundra would first be invaded by conifer forests, but that the proportion of broad‐leaved deciduous forest would increase, reflecting increased fire frequency, as climatic warming continued. The change in fire frequency was determined more strongly by climatically driven changes in vegetation than by direct climatic effects on fire probability. The pattern of climatic warming was more important than the rate of warming or change in precipitation in determining the rate of conversion from tundra to forest. Increased climatic variability promoted ecosystem change, particularly when oscillations were long relative to the time required for tree maturation. Management policies related to logging and moose‐predator control affected vegetation as much or more than did changes in climate and must be included in future scenarios of global changes in ecosystem distribution. We suggest that frame‐based models provide a critical link between patch and equilibrium models in predicting ecosystem change in response to transient changes in climate over the coming decades to centuries.

Diagnosing climate variability and environmental change in floodable regions is essential for understanding and mitigating impacts on natural ecosystems. Our objective was to characterize environmental degradation in the Brazilian Pantanal by identifying changes in vegetation and water cover over a 30-year period using remote sensing techniques. We evaluated surface physical–hydric parameters, including Land Use and Land Cover (LULC) maps, Normalized Difference Vegetation Index (NDVI), Modified Normalized Difference Water Index (MNDWI), Normalized Difference Moisture Index (NDMI), and precipitation data. There was a decrease in the area of water bodies (−9.9%), wetlands (−5.7%), and forest formation (−3.0%), accompanied by an increase in the area of pastureland (7.4%). The NDVI showed significant changes in vegetation cover (−0.69 to 0.81), while the MNDWI showed a decrease in water surface areas (−0.73 to 0.93) and the NDMI showed a continuous decrease in vegetation moisture (−0.53 to 1). Precipitation also decreased over the years, reaching a minimum of 595 mm. Vegetation indices and land use maps revealed significant changes in vegetation and loss of water bodies in the Pantanal, reinforcing the need for sustainable management, recovery of degraded areas, and promotion of ecotourism to balance environmental conservation and local development.

Northern ecosystems contain up to 455 Gt of C in the soil active layer and upper permafrost. The soil carbon in these layers is equivalent to approximately 60% of the carbon currently in the atmosphere as CO2. Much of this carbon is stored in the soil as dead organic matter. Its fate is subject to the net effects of global change on the plant and soil systems of northern ecosystems. The arctic alone contains about 60 Gt C, 90% of which is present in the soil active layer and upper permafrost. The arctic is assumed to have been a sink for CO2 during the historic and recent geologic past. The arctic has the potential to be a very large, long-term source or sink of CO2 with respect to the atmosphere. In situ experimental manipulations of atmospheric CO2, indicated that there is little effect of elevated atmospheric CO2 on leaf level photosynthesis or whole-ecosystem CO2 flux over the course of weeks to years, respectively. However, there may be longer-term ecosystem responses to elevated CO2 that could ultimately affect ecosystem CO2 balance. In addition to atmospheric CO2, climate may affect net ecosystem carbon balance. Recent results indicate that the arctic has become a source of CO2 to the atmosphere. This change coincides with recent climatic variation in the arctic, and suggests a positive feedback of arctic ecosystems on atmospheric CO2 and global change. Measurements along a latitudinal gradient across the north slope of Alaska indicate a loss of carbon from tussock tundra of 156 g m-2 y-1, and from the wet tundra of 34 g m-2 y-1. If these rates are representative of the circumpolar tundra, then they equate to a net annual global loss of carbon as CO2 to the atmosphere of 0.17 Gt C, 0.14 Gt from tussock tundra, and 0.03 Gt from wet coastal tundra. Depending on the nature, rate, and magnitude of global environmental change, the arctic may have a positive or negative feedback on global change. At present, the initial response of the arctic indicates a net loss of carbon to the atmosphere which could result in a positive feedback on atmospheric C02 concentration and greenhouse warming. There are obvious potential errors in scaling plot level measurements to landscape, mesoscale, and global spatial scales. The research proposed in this application has four principal aspects: (A) Long-term response of arctic plants and ecosystems to elevated atmospheric CO2; (B) Circumpolar patterns of net ecosystem CO2 flux; (C) In situ controls by temperature and moisture on net ecosystem CO2 flux; (D) Scaling of CO2 flux from plot, to landscape, to regional scales (In conjunction with research proposed for NSF support). In Iceland, we will evaluate the long-term (hundreds to thousands of years) effect of atmospheric CO2 enrichment from cold, CO2-rich springs on plant photosynthesis, ecosystem CO2 flux, and community composition and structure. CO2 flux estimates at a circumpolar scale will be initiated with research in the Russian arctic and Iceland (measurements in Iceland will be obtained in the process of determining the long-term effect of elevated CO2 on arctic ecosystems). Temperature and moisture will be manipulated in the field to determine their effects on net ecosystem CO2 flux. In cooperation with a project proposed for funding from NSF's ARCSS LAII program, measurements of CO2 and other trace gas flux at three spatial scales (plot, landscape, and mesoscale) using chamber, tower-based eddy correlation techniques and aircraft-based eddy correlation techniques will be made. The information obtained from each of these techniques will be analyzed and compared, especially in light of defining the most efficient approaches for estimating large spatial scale CO2 in the arctic. Remotely-sensed spectral indices, GIS, process models, and phenomenological models will be used to develop a methodology for efficiently estimating ecosystem CO2 flux over meso- and global scales. Initial testing of the applicability of these methods will be undertaken. Support from the Department of Energy is requested for plat level measurements. support from NSF is also requested for other aspects of scaling.

QuestionsBush encroachment, (i.e. disproportionate woody vegetation increase at the cost of grassland) has negative impacts for biodiversity conservation and tourism by homogenising habitat structure and decreasing grazing and game‐viewing. While herbivory, rainfall, and CO2 all influence changes in woody vegetation cover, fire has the best potential for vegetation management. Changes in fire management can either encourage or suppress bush encroachment and a better understanding of how changes in fire regime affect vegetation structure is needed. Therefore, this study addressed three questions: (a) how has woody cover changed over two decades (1999–2019); (b) what is the role of land use, rainfall, and fire in influencing woody cover change; and (c) what are the management implications?LocationBwabwata National Park (BNP), Namibia.MethodsThe study used a novel combination of repeat ground photography and satellite‐based remote‐sensing products to explore the change in woody vegetation in relation to rainfall, land use, and fire seasonality.ResultsWoody vegetation has increased by 13% since 1999 in BNP. Change in vegetation structure differed in the east and west of the park. Early‐season burns in the east of the park were associated with an increase in trees over 3 m tall consisting primarily of Dialium englerianum, Terminalia sericea and Burkea africana. Repetitive late dry‐season fires in the west of the park were associated with an increase in shrubs under 3 m dominated by Baphia massaiensis and Terminalia sericea.ConclusionsBoth early‐ and late‐season fires are of value in management of bush encroachment. Early dry‐season fires appear to reduce the rate of bush encroachment and contribute to maintaining a heterogeneous vegetation structure. This fire management strategy reduces wildfire risk, conserves biodiversity, and promotes tourism and is, therefore, recommended for the park.

Anthropogenic drivers of global change include rising atmospheric concentrations of carbon dioxide and other greenhouse gasses and resulting changes in the climate, as well as nitrogen deposition, biotic invasions, altered disturbance regimes, and land-use change. Predicting the effects of global change on terrestrial plant communities is crucial because of the ecosystem services vegetation provides, from climate regulation to forest products. In this paper, we present a framework for detecting vegetation changes and attributing them to global change drivers that incorporates multiple lines of evidence from spatially extensive monitoring networks, distributed experiments, remotely sensed data, and historical records. Based on a literature review, we summarize observed changes and then describe modeling tools that can forecast the impacts of multiple drivers on plant communities in an era of rapid change. Observed responses to changes in temperature, water, nutrients, land use, and disturbance show strong sensitivity of ecosystem productivity and plant population dynamics to water balance and long-lasting effects of disturbance on plant community dynamics. Persistent effects of land-use change and human-altered fire regimes on vegetation can overshadow or interact with climate change impacts. Models forecasting plant community responses to global change incorporate shifting ecological niches, population dynamics, species interactions, spatially explicit disturbance, ecosystem processes, and plant functional responses. Monitoring, experiments, and models evaluating multiple change drivers are needed to detect and predict vegetation changes in response to 21st century global change.

Modification of the Earth’s surface i.e. land use change, is the main human activity for survival and is the key player in the management of natural resources, including water. Little attention has, however, been given to understand the role the territorial vegetation changes may play in strategic management of water resources. In the basin of Aswa northern Uganda, the changes in land use due to complex demographic and social economic factors is among the numerous challenges faced in management of the limited water resources in the area. The aim of the current study was to explore the opportunities land use changes in the basin may offer to water resources management, looking mainly at the expansion in future agriculture and afforestation as the critical land use change issues. The study was structured into four broad objectives: The first objective was to generate the reference land use dataset (1986 & 2001). The available techniques (the supervised and the unsupervised image classification) were explored using Landsat multi-spectral images. Through careful evaluation, the supervised image classification with the best classification accuracy of 81.48% was used to generate 1986 and 2001 land use maps. The second objectives of the study was to generate experimental land use scenarios required for testing the effect of spatial land use policies on hydrologic processes in the basin. The Multi-criteria-GIS methodology was developed and six experimental land use scenarios were generated using simple but consistence set of bio-physical and socio-economic parameters. The third objective was to customise the hydrologic process model SWAT that was used to simulate the hydrologic impact of the land use change scenarios. The calibration of the hydrologic model SWAT used monthly historical streamflow records from 1970 to 1974 recorded at the basin outlet. The model was manually calibrated using the Nash-Sutcliffe coefficient as objective function. The efficiency of the model during calibration was 0.46. Validation of the model using an independence monthly streamflow records from 1975 to 1978 was done and the model efficiency was 0.66, much better than in calibration period. The forth and last objective of the study was to simulate the hydrologic processes in the reference years and the hydrologic processes impacted by the land use change scenarios and to evaluate how this impact affects water resources management strategies. An independent validation of the model to identify the validity of extending the optimal parameters set in simulation of 2001 and land use change hydrologic processes was carried out by comparing the simulated actual evapotranspiration fraction with estimated actual evapotranspiration fraction obtained using surface energy balance method and the thermal MODIS images. Validation indicated acceptable model performance in simulating 2001 hydrologic processes, with a spatial correlation coefficient of 0.45. The application of the model in simulations of the hydrologic processes in the reference years noted that 2001 had more water yield than 1986 by 9.2 mm. The analysis of the impact of land use change in the reference years indicated an increase of 2.52 mm of water yield in the year 2001. Simulation of the hydrologic impact of the experimental land use indicated that Land use types, which in this study were restricted to plantation forest and generic agriculture, land use extent and location of the land use with respect to precipitation rate and amount, greatly influence the hydrologic process of the basin and the net water yield. It was noted that the water yield of the basin can be significantly decreased by over 15%, if more than 37% of the plantation forests are introduced in the wet zone. In the dry sub-basins however, afforestation of up to 42% had insignificant effect on water yield, which could therefore be exploited so as to offset the afforestation pressure in the wet sub-basin while at the same time enhancing the basin water yield. The effect of agricultural land use change on water yield was however less sensitive to climatic zones. 53% increase in agricultural land cover responded with an increase in water yield by about 27%.

Lassa Fever is endemic to the eastern region of Sierra Leone. It is a haemorrhagic disease that is often transmitted from rats to humans and then human to humans. Ecological disturbances such as changes in land use involving conversion of natural ecosystems to agriculture, mining or for urban expansion are reported to bring humans into close contact with animals such as the Mastomys rat that carries the Lassa Fever virus thereby posing health problems.The nature and extent of such ecological disturbances or land use changes within areas known to be endemic to Lassa Fever are not clearly understood from a research context in Sierra Leone. This study was therefore undertaken to identify the pattern of changes in land use and cropping practices and their potential to bring humans into close interactions with the Mastomys rat that is the host for the Lassa Fever virus. Four communities were chosen for the study, two rural (Lalehun and Majihun) and two urban (Lambayama section in Kenema City and Largo Square section in Segbwema Town). Different vegetation and land use/cropping practices were identified and observations were made on the pattern of changes at different times in the cropping year. There were four common vegetation and cropping practices found in all communities: upland rice intercropping, old fallow, young fallow, and swamp rice cultivation. The study revealed the variations in land use patterns and cropping practices between urban and rural settlements. Agro-forestry practices such as perennial cash crops cacao and rubber plantations were more common in rural communities. The study also revealed that while fallow vegetation persisted in rural areas there had been expansion of settlements into old fallow vegetation indicating a greater threat to the persistence of natural ecosystem in urban than in rural settlements. These disturbances resulted in habitat fragmentation and increased the likelihood of contact between humans and animal species (e.g. Mastomys rat) associated with various habitats.