201 research outputs found

    Afforestation and Reforestation: Drivers, Dynamics, and Impacts

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    Afforestation/reforestation (or forestation) has been implemented worldwide as an effective measure towards sustainable ecosystem services and addresses global environmental problems such as climate change. The conversion of grasslands, croplands, shrublands, or bare lands to forests can dramatically alter forest water, energy, and carbon cycles and, thus, ecosystem services (e.g., carbon sequestration, soil erosion control, and water quality improvement). Large-scale afforestation/reforestation is typically driven by policies and, in turn, can also have substantial socioeconomic impacts. To enable success, forestation endeavors require novel approaches that involve a series of complex processes and interdisciplinary sciences. For example, exotic or fast-growing tree species are often used to improve soil conditions of degraded lands or maximize productivity, and it often takes a long time to understand and quantify the consequences of such practices at watershed or regional scales. Maintaining the sustainability of man-made forests is becoming increasingly challenging under a changing environment and disturbance regime changes such as wildland fires, urbanization, drought, air pollution, climate change, and socioeconomic change. Therefore, this Special Issue focuses on case studies of the drivers, dynamics, and impacts of afforestation/reforestation at regional, national, or global scales. These new studies provide an update on the scientific advances related to forestation. This information is urgently needed by land managers and policy makers to better manage forest resources in today’s rapidly changing environments

    Variations and controlling factors of vegetation dynamics on the Qingzang Plateau of China over the recent 20 years

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    The impacts of climate change and human activities on vegetation dynamics have attracted wide attention, especially in sensitive and vulnerable areas such as the Qingzang Plateau of China. In this region, a series of ecological restoration projects have been launched while the effectiveness of these projects requires evaluation and further improvements. Remote sensing with high temporal resolution and spatial coverage is an effective way for the vegetation dynamics research in this region. In this study, the spatial and temporal distribution of climate factors and vegetation coverage as well as the influencing factors such as air temperature, precipitation, land use, slope, slope direction, soil and altitude were analyzed. The geographical detector was used to analyze the influence of climate factors on vegetation coverage and the interaction among factors in different eco-geographical regions. The results showed that: 1) the average values from the 20 years of normalized difference vegetation index (NDVI) decreased gradually from southeast (> 0.61) to northwest (0.12). The overall average of NDVI increased 0.02 per year from 1998 to 2018 and the impact factors varied among different eco-geographical regions; 2) some controlling factors showed nonlinear enhancement such as altitude and slope; 3) land use was an important factor affecting the distribution of vegetation especially in humid, semi-arid and arid areas, but the impacts of elevation and temperature were stronger than land use types in semi-humid and humid areas. The design and construction of ecological protection and restoration projects on the Qingzang Plateau required scientific and detailed demonstration as well as monitoring and evaluation. In addition, new tools and theories were also needed in the selection of ecosystem restoration strategies. Based on the findings, this study also provides suggestions for the sustainable ecological restoration on the Qingzang Plateau

    Land Use Conflict Detection and Multi-Objective Optimization Based on the Productivity, Sustainability, and Livability Perspective

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    Land use affects many aspects of regional sustainable development, so insight into its influence is of great importance for the optimization of national space. The book mainly focuses on functional classification, spatial conflict detection, and spatial development pattern optimization based on productivity, sustainability, and livability perspectives, presenting a relevant opportunity for all scholars to share their knowledge from the multidisciplinary community across the world that includes landscape ecologists, social scientists, and geographers. The book is systematically organized into the optimization theory, methods, and practices for PLES (production–living–ecological space) around territorial spatial planning, with the overall planning of PLES as the goal and the promotion of ecological civilization construction as the starting point. Through this, the competition and synergistic interactions and positive feedback mechanisms between population, resources, ecology, environment, and economic and social development in the PLES system were revealed, and the nonlinear dynamic effects among subsystems and elements in the system identified. In addition, a series of optimization approaches for PLES is proposed

    Vegetation Dynamics Revealed by Remote Sensing and Its Feedback to Regional and Global Climate

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    This book focuses on some significant progress in vegetation dynamics and their response to climate change revealed by remote sensing data. The development of satellite remote sensing and its derived products offer fantastic opportunities to investigate vegetation changes and their feedback to regional and global climate systems. Special attention is given in the book to vegetation changes and their drivers, the effects of extreme climate events on vegetation, land surface albedo associated with vegetation changes, plant fingerprints, and vegetation dynamics in climate modeling

    Soil Erosion in a Highly Dynamic, Terraced Environment - the Effect of the Three Gorges Dam in China

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    Worldwide, soil erosion is one of the most pressing environmental problems of present times. Particularly, soil erosion triggered by overland flow and runoff seriously affects the productivity and stability of ecosystems. The loss of fertile topsoil and soil's water storage capacity, and the discharge of sediments and associated contamination of waterbodies due to diffuse matter transport of particle-bounded agrochemicals from cropland highly elicit call a for action to combat soil erosion for a future securing of food supply and high drinking water quality. Globally, China belongs to one of those countries most affected by soil erosion. Technical problems as well as high economic off-site damages and costs resulting from reservoir siltation and thus, reduced project's lifespan due to soil erosion are typical for numerous large-scale dam projects in China. In addition to the natural disposition to soil erosion, especially, anthropogenic impacts associated to the dam construction distinctly affect the soil erosion risk potential in the adjacent ecosystems. This can be exemplarily seen at the currently worldwide largest dam project, the Three Gorges Dam at the Yangtze River in Central China. This megaproject has been controversially discussed since its planning, and most recently since its construction and full operation in 2007. It contains the largest installed hydropower capacity worldwide, and is supposed to distinctly improve the river navigation and to secure the water supply to the northern country in the long-term. The realization of the dam project has already required massive resettlements of rural and urban population of more than one million people long before its start of operation. Additionally, large-scale land use changes, e.g., land reclamation for the road and settlement construction, for small scale subsistence farming and for cash crop production as well as shifts in land uses, on the steep sloping uphill-site above the impounded area are expected to considerably foster the soil erosion in the short- to long-term. Due to their partially direct connection to the stream network agriculturally used land with high soil erosion potential affects the water quality. Precise knowledge on the quality and quantity of soil loss, and its spatial and temporal variability can help to control the soil erosion by developing an adapted land use management and identifying conducive soil conservation measures, such as contour-aligned bench terraces. Under optimum conditions, bench terraces balance the geomorphic settings and anthropogenic use and can present a fair and sound basis for economic growth in mountainous areas. The focus of the present thesis lies on the risk potential of soil erosion by water in the newly created reservoir of the Three Gorges Dam. Therefore, the central research questions aimed at the natural soil erosion risk potential and the effect of the dam-induced land use dynamics on the dimension and spatial and temporal distribution of soil losses. Due to the data scarcity and limited access to the terrain, a further focus of the research conducted lied on the data-based regionalization of soil erosion factors to use as input in soil erosion modeling. The research was conducted in the subtropical Xiangxi catchment (3,200 km²) that was considered to adequately represent the Three Gorges Area in terms of physical settings and human interventions attributing to the dam project. The Xiangxi River joins the Yangtze River as a first class tributary approximately 40 km upstream the Three Gorges Dam. Due to the dam construction, the widely terraced landscape of the Xiangxi catchments is also affected by rapid, high land use dynamics with consequences on the slope stability. Particularly, the backwater area in the southern catchment area with the impounded lower reach of the Xiangxi River is characterized by steep to extremely steep sloping terrain and predominantly shallow soils with moderate to very high soil erodibility. Additionally, the very high rainfall erosivity increases the high physical vulnerability of the entire Xiangxi catchment. Between 1987 and 2007, a governmental-driven decrease of arable land and an increase of woodland and shrubland affected the northern headwater zone of the catchment. In the immediate reservoir area, the land use change from 1987 to 2007 was mainly controlled by a distinct conversion of arable land to orange orchards. Within the framework of this thesis, methods for data survey and data processing were tested and adapted in order to evaluate the risk potential of soil erosion. In addition, comprehensive field investigations focusing on soil erosion processes and on pedological properties and further erosion-relevant factors were conducted. Relevant parameters derived from remote sensing data and land use classifications as well as the documented land use change from 1987 to 2007 were used for the parameterization of the empirical soil erosion model RUSLE. This model was applied to estimate and evaluate the spatial distribution and dynamic of the soil erosion risk potential, and to spatially localize high-risk areas. The new conceptual model TerraCE was developed and tested for the identification and spatial analysis of different terrace conditions and their causes. By means of data mining approaches, a prediction of the spatial distribution of the identified terrace conditions was computed. By integrating environmental and anthropogenic indicators on the impact of the terrain and the human influence, the causes and the strength of disturbances on the terrace conditions, and thus terrace degradation were analyzed. During the observation period from 1987 to 2007, the Xiangxi catchment is generally characterized by a decrease of average annual soil losses and their maxima due to implemented environmental programs. However, a very high soil erosion risk potential in the entire catchment must be assumed. Frequency and intensity of soil erosion mainly concentrate in the backwater area at the lower reaches of the Xiangxi River. Here, land use changes, resettlements, and infrastructure construction have the highest impact. An inadequate construction of terraces that is not adapted to the local terrain conditions and an insufficient maintenance of the farming terraces can further strongly affect the soil erosion dynamic. Moreover, rapid ecosystem changes and an associated intensification and reclamation of terraces can lead to their degradation. The tempo of the land use dynamics hardly considers available capital and labor for the cost and time-consuming restoration and maintenance of terraces, mainly cultivated with oranges. The high increase of the reclaimed area for the orange production within very short term caused a surplus production and thus, a price decline on the local and regional markets. Due to the not very profitable sale of oranges, a lack of farmers' motivation and little or no capital are made responsible for the gradual worsening of the terrace conditions. As many of the resettled peasants, that were formerly used to farm the flat valley bottoms, are often not familiar with the new and difficult terrain settings and farming techniques, there is also a lack of knowledge on adequate terrace cultivation. Subsequently, inappropriate management of those terraces leads to an increase in the soil erosion The findings of the present thesis suggest designating the terraces as important, sensitive ecosystem service as they present - if properly maintained - a very effective soil erosion control and enable for a sustainable land use in the mountainous Xiangxi catchment and throughout the entire Three Gores Area. Considering the data scarcity in terms of spatial and temporal resolution, the results further show that soil erosion factors can be successfully regionalized and used for a valid soil erosion modeling. Against the background of ongoing research within the 'Yangtze Project' as well as further projected large dam projects at the Yangtze River and worldwide, the research conducted offers an important starting point for further research on the soil erosion risk potential and associated environmental threats, such as water pollution

    Modelling in ungauged catchments using PyTOPKAPI : a case study of Mhlanga catchment.

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    Masters Degree. University of KwaZulu-Natal, Durban.Hydrological modeling of rainfall-runoff processes is a powerful tool used in various water resources applications, including the simulation of water yield from ungauged catchments. Many rivers in developing countries are poorly gauged or fully ungauged. This gives rise to a challenge in the calibration and validation of hydrological models. This study investigated the applicability of PyTOPKAPI, a physically based distributed hydrological model, in simulating runoff in ungauged catchments, using the Mhlanga River as a case study. This study is the first application of the PyTOPKAPI model to simulate daily runoff on an ungauged catchment in South Africa. The PyTOPKAPI model was parameterised using globally available digital elevation data (DEM), satellite-derived land cover, soil type data and processed hydro-meteorological data collected from various sources. Historical 30-year (1980-2009) quaternary monthly streamflow (from a well-tested and calibrated model) and daily meteorological variables (rainfall, temperature, humidity and so on) were obtained. The rainfall data were subjected to double mass curve test to check for consistency. The monthly streamflow was transposed to the catchment and disaggregated to daily streamflow time step. The PyTOPKAPI model was calibrated using an average runoff ratio as an alternative to matching streamflow data that is usually used for model calibrations. The simulated results were thereafter compared with the disaggregated monthly quaternary data. The model results show good overall performance when compared with the average runoff ratio, monthly disaggregated streamflow and the expected mean annual runoff in the catchment. In general, PyTOPKAPI can be used to predict runoff response in ungauged catchments, and thus may be adopted for water resources management applications

    Climate Change and Environmental Sustainability-Volume 4

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    Anthropogenic activities are significant drivers of climate change and environmental degradation. Such activities are particularly influential in the context of the land system that is an important medium connecting earth surface, atmospheric dynamics, ecological systems, and human activities. Assessment of land use land cover changes and associated environmental, economic, and social consequences is essential to provide references for enhancing climate resilience and improving environmental sustainability. On the one hand, this book touches on various environmental topics, including soil erosion, crop yield, bioclimatic variation, carbon emission, natural vegetation dynamics, ecosystem and biodiversity degradation, and habitat quality caused by both climate change and earth surface modifications. On the other hand, it explores a series of socioeconomic facts, such as education equity, population migration, economic growth, sustainable development, and urban structure transformation, along with urbanization. The results of this book are of significance in terms of revealing the impact of land use land cover changes and generating policy recommendations for land management. More broadly, this book is important for understanding the interrelationships among life on land, good health and wellbeing, quality education, climate actions, economic growth, sustainable cities and communities, and responsible consumption and production according to the United Nations Sustainable Development Goals. We expect the book to benefit decision makers, practitioners, and researchers in different fields, such as climate governance, crop science and agricultural engineering, forest ecosystem, land management, urban planning and design, urban governance, and institutional operation.Prof. Bao-Jie He acknowledges the Project NO. 2021CDJQY-004 supported by the Fundamental Research Funds for the Central Universities and the Project NO. 2022ZA01 supported by the State Key Laboratory of Subtropical Building Science, South China University of Technology, China. We appreciate the assistance of Mr. Lifeng Xiong, Mr. Wei Wang, Ms. Xueke Chen, and Ms. Anxian Chen at School of Architecture and Urban Planning, Chongqing University, China
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