Rehabilitation of grasslands after eradication of alien invasive trees

Invasive alien plants (IAPs) remain a serious threat to the water supply and to stor-age reservoirs throughout South Africa. IAPs are known to use a large quantity of water through evapotranspiration, and the clearing and control of IAPs has been a major activity of the Working for Water (WfW) programme. Successful clearing of these often aggressive woody trees and shrubs requires careful regeneration of ef-fective indigenous vegetation cover after the physical clear-felling and removal of the IAPs. Application of effective post-clearing management regimes is required in order to improve the grass cover within catchments and this can ensure that there is controlled runoff and groundwater re-charge. South Africa's water catchment areas receive insufficient rainfall (Blignaut and De Wit 2004). In addition, limited options for the construction of new reservoirs and water schemes has stimulated the need to explore other options for increasing and conserving water supplies (Ashton and Seetal 2002) and improved demand management

Influence of land cover degradation on the water balance of the Northern Drakensberg high altitude mesic grasslands, South Africa.

Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.Mountainous regions provide vital ecosystem services, such as water provisions to low land areas. However, these regions are also considered sensitive to the effects of environmental change, due to their high levels of endemism and biodiversity. Thus, environmental change within these regions could have significant consequences beyond the extent of the region itself. An important implication of environmental change is the impact a change in land cover could have on the water balance of a catchment, especially within the headwater catchments. The Drakensberg mountains in South Africa, is such a mountain region, which is vital for its provision of ecosystem services and generation of water resources. This mountainous region is under threat from anthropogenic environmental change. The Drakensberg mountain range has been identified within South Africa as a strategic water source area (SWSA) and within the Northern-Drakensberg SWSA exists the Maloti-Drakensberg Park, which is a protected area managed by Ezemvelo KZN Wildlife and a World Heritage site. The Northern-Drakensberg mountain range natural grasslands are under threat from two forms of land cover change degradation, that of woody encroachment and following disturbance, invasion of bracken fern. Woody encroachment occurs within the natural grasslands following the removal of fire, which is of concern within the protected areas, where fire is a current management tool to maintain the natural grassland cover. Outside the protected area, disturbances due to human activities such as overgrazing and poor land management have led to a substantial level of degradation occurring, providing ideal conditions for the invasion of bracken fern. To safeguard and maintain the assurance of supply from an important SWSA of South Africa, there is the need for improved understanding on the impacts of land cover change and degradation within the Northern-Drakensberg mountain range on the water balance of the region. Thus, the overall aim of this thesis is to understand the influence of land cover change related degradation on the water balance of the Northern-Drakensberg high-altitude mesic grasslands and what this in turn means for the water supply generated from this SWSA of South Africa. To achieve the main aim, the research was scaled from a point measurement to a basin scale where management decisions are made. To improve our understanding of the impact of degradation related land cover change on the water balance an observational approach is required. Located within the Maloti-Drakensberg Park is the long-term Cathedral Peak research catchments which provided the platform for the observation component of this research. Of interest in the Cathedral Peak research catchments were three hydrologically individual catchments. Catchment III which consists of a degraded bracken fern land cover following the historical research experiments within the catchment on the impacts of commercial Pinus patula plantation on streamflow. Despite rehabilitation efforts following the removal of the plantation, the catchment transitioned to a degraded state and is currently near-completely invaded with bracken fern. Catchment VI which is under natural grassland condition, is managed with a bi-annual spring burn as proven best practice within the Drakensberg region. This catchment formed the baseline catchment for this research. Catchment IX is a woody encroached land cover following the protection of fire since the 1950s as part of research into the implications of removing fire from the natural grasslands. These three catchments provided the ideal platform from which the change in water balance components under each land cover could be monitored and investigated. The process of evapotranspiration (ET), which forms the connection between the energy and water balances, is well understood to be one of the most affected components of the water balance following a change of land cover. Therefore, ET was the focus of the initial point observation research. Due to the cost and stringency of the prominent method for ET measurement of eddy covariance (EC), an alternative more financially feasible method of surface renewal (SR) was tested over both Leucosidea sericea (woody) and Pteridium aquilinum (bracken) vegetation in comparison to EC. It was determined that the SR method, and in particular the SR dissipation theory (SRDT) method, which is independent of EC, was the best alternative and cheapest method to EC. The SR method is now used within the Cathedral Peak research catchments for long-term estimations of ET over both vegetation canopies. During this research, calibration factors (α) for the surface renewal 1 (SR1) method were determined for both the Leucosidea sericea (woody) and Pteridium aquilinum (bracken) vegetation types for winter and summer. Having confirmed the SRDT ability as an alternative to EC, the seasonal ET of Leucosidea sericea (woody) and Pteridium aquilinum (bracken) was determined. Providing first insight into the seasonality of ET over these vegetation types. Both vegetations followed a similar seasonal ET cycle to the natural grasslands, with the largest difference occurring in winter when the grasslands become dormant. It was also found that the energy balance was altered under the degraded land covers, with both forms increasing available energy and latent heat flux. Following the understanding of the seasonal change in ET through point measurements, the research focus was scaled up to the research catchment. A comparison of catchment VI and IX was conducted to identify changes in the headwater catchment water balance between the natural grassland and woody encroachment land covers. Long-term data sets of precipitation and streamflow from the Cathedral Peak research catchments, in combination with the seasonal ET observations showed that over time, as woody encroachment increased, the catchment rainfall:runoff response ratio decreased, as did streamflow under woody encroachment compared to natural grassland. Having gained an understanding of the impacts on a water balance of a headwater catchment, hydrological modelling in combination with scenario analysis was used to understand the impacts on water supply from the upper-uThukela catchment were both land cover degradation threats left unmanaged. Land cover parameters were unavailable for Leucosidea sericea (woody) and Pteridium aquilinum (bracken), and therefore were derived from understanding gained during observation. The ACRU agrohydrological model was utilised and confirmed to simulate current land cover conditions within the upper-uThukela satisfactorily at both the headwater and catchment levels. It was identified that both forms of land cover change resulted in a reduction in streamflow. This was largest for woody encroachment. The most affected flows were the low flows and winter dry period flows. Headwater catchments were also identified as the most impacted by land cover change. The key conclusions of the research were: • that the surface renewal methodology is a viable alternative for obtaining estimates of evapotranspiration over indigenous vegetation types; • that the energy balance and ET of woody vegetation in comparison to the natural grassland was significantly altered; • the importance of fire, as not only a management tool for the maintenance of the natural grasslands, but also to ensure the sustainability of the vital water resources and ensuring water security; • that there is an evident lag between the onset of degradation in the form of woody encroachment and the resultant impacts on streamflow; • the disproportionally large impact degradation related land cover change within these headwater catchments has on the downstream water balance relative to low land catchments. Following the analysis and with the understanding gained, it is recommended that the natural grasslands continue to be managed using fire, and continued protection of the natural grasslands needs to be maintained. Observation within these headwaters is key to improving the understanding of change and to drive decision making, allowing for the optimal management of the important SWSA.Author's Publications listed on pages iv-v

An Integrated Approach to Assessing Spread of Commercial Horticulture and Related Environmental Impacts on Watersheds : Cases in Central Highlands of Kenya

Intensive horticulture production has broad environmental implications due to the high dependency on natural resources. Numerous reports indicate positive socio-economic gains associated with the Kenyan horticulture sub-sector. Even so, few highlight the extent of the negative environmental impacts. We adopt a holistic approach that integrates deskwork, Geographical Information Systems (GIS), field study and remote sensing tools to evaluate the spread and growth of commercial horticulture, and the effects on: i) surface water quality, and ii) vegetation condition, in watersheds experiencing increased production within the central highlands. The desk research utilized Google Earth archives and GIS data, to map greenhouse distribution, determining area under production and factors predicting choice of location. This was followed by a field study to sample and characterize surface water quality in select sub-watersheds with intensive horticulture, thereby highlighting potential pollutant source-processes. Twenty five years of remote sensing data were also analyzed to establish vegetation condition and responses to increased farming and human disturbances. This was followed by a detailed study to quantify land use and land cover changes, and finally a chapter illustrating trends in horticulture exports volumes. Results from the desk research showed heterogeneous spread of farming, where area under production increased rapidly between 2000 and 2011. Population density, average slope, average rainfall and dams were significant predictors to farming location. Results from the field study show predominance of anthropogenic trace elements of cadmium, phosphate, and zinc in waters draining from regions with intensive large scale horticulture. The long-term vegetation study indicates spatially varying inter-annual NDVI, which continuously declined post 1990s in sub watersheds with increased farming. The study to quantify land transformation dynamics, indicate varying magnitudes of change with rates of change differing between land-uses, and between case studies, attributable to socio-economic drivers. We also find that horticultural exports had positive trends until 2008/2009, and 2010, where the effects of post-election violence and volcanic eruption are evident. Overall, the research has demonstrated the efficacy of integrated approaches in understanding implications intensified production on watershed resources. This knowledge is important in developing policies and regulatory frameworks that supports sustainable resource utilization and best management practices

Assessing land use-land cover changes and their effects on the hydrological responses within the Nyangores River Catchment, Kenya

Philosophiae Doctor - PhDThis thesis aimed at contributing knowledge on how the widespread changes in land use/cover resulting from increasing human population and their associated activities, are influencing hydrological responses in a sub-humid catchment. The study therefore hypothesised that reduced forest cover over time in favour of agricultural activities is altering hydrological processes of the catchment which is affecting the flow characteristics in a sub-humid catchment. The sub-humid catchment selected to investigate these issues is the Nyangores River Catchment in Kenya

Soil threats in Europe

Although there is a large body of knowledge available on soil threats in Europe, this knowledge is fragmented and incomplete, in particular regarding the complexity and functioning of soil systems and their interaction with human activities. The main aim of RECARE is to develop effective prevention, remediation and restoration measures using an innovative trans-disciplinary approach, actively integrating and advancing knowledge of stakeholders and scientists in 17 Case Studies, covering a range of soil threats in different bio-physical and socio-economic environments across Europe. Existing national and EU policies will be reviewed and compared to identify potential incoherence, contradictions and synergies. Policy messages will be formulated based on the Case Study results and their integration at European level. A comprehensive dissemination and communication strategy, including the development of a web-based Dissemination and Communication Hub, will accompany the other activities to ensure that project results are disseminated to a variety of stakeholders at the right time and in the appropriate formats to stimulate renewed care for European soils.JRC.H.5-Land Resources Managemen

Assessing climate change impacts on productivity of sugarbeet and sugarcane using aquacrop.

Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.Globally, the use of biofuels has grown over the years and their importance in helping to reduce a) dependency on fossil-based fuels and b) greenhouse emissions has been widely recognised. Various feedstocks are used for biofuels, viz. sugar-based crops for bioethanol production and oil from vegetable crops for biodiesel production. The research presented in this study focused on sugar crops such as sugarcane and sugarbeet. The sugarcane industry is widely established in South Africa, whereas sugarbeet is still a new crop and hence, there is little information on its water use efficiency (WUE) and potential yields under South African growing conditions. Overall, there is a need to better understand the agricultural potential and water use requirements of these feedstocks, in order to grow the biofuels industry in South Africa in a sustainable manner. Furthermore, climate change poses a threat to global food security as well as to biofuel feedstock production. There are uncertainties regarding the potential impacts of climate change on the yield and WUE of agricultural crops. One of the main objectives of this study was to calibrate the AquaCrop crop model for sugarcane and sugarbeet using experimental datasets. This study then followed a modelling approach to estimate dry yields and WUEs of these two sugar feedstocks to add to the existing knowledge base for potential biofuel production in South Africa. Sugarbeet was planted at the Ukulinga research farm and field equipment was used to collect data for the calibration of the crop model to better estimate attainable yield and WUE. Growth and yield datasets were provided by the South African Sugarcane Research Institute to calibrate the model for sugarcane, as well as validate AquaCrop for both feedstocks. The performance of the crop model was tested using various statistical methods. The model’s performance was satisfactory after calibrating it for sugarcane. However, the calibration process was compromised by the lack of sufficient leaf area index data. For sugarbeet, AquaCrop simulated the canopy cover, yield and WUE well, but tended to over-estimate observations. For the validation process, simulations closely matched the observed yields for both feedstocks. However, the model’s ability to simulate soil water content at Ukulinga was considered unsatisfactory. The calibrated AquaCrop model was used for long term assessments of yield and WUE. Baseline simulations were undertaken using 50 and 30 years of climate data and the results indicated that the 30 years of data could adequately estimate the long-term attainable productivity of sugarcane and sugarbeet. According to the literature, an ensemble approach to climate change modelling reduces uncertainty in long-term assessments. Hence, climate projections from several global climate models (GCMs), that were downscaled using dynamical and statistical approaches, were obtained and used to assess the potential impacts of climate change on yield and WUE of the selected feedstocks. An increase in yield and WUE of both feedstocks is projected in the distant future. The statistically downscaled GCMs projected higher increases compared to the dynamically downscaled GCMs. Increases in future WUE are much higher compared to yields projections. The so-called “CO2 fertilisation” effect largely benefits C3 crops (sugarbeet) with regards to yield improvements. However, the results also show that C4 crops (sugarcane) also benefit from improved WUE. Both sugarcane and sugarbeet will benefit from the anticipated climate change when planted in February and May, respectively. However, it is recommended that other planting dates should be studied for sugarcane

Forest Management and Water Resources in the Anthropocene

Decades of research has provided a depth of understanding on the relationships among forests and water, and how these relationships change in response to climate variability, disturbance, and forest management. This understanding has facilitated a strong predictive capacity and the development of best management practices to protect water resources with active management. Despite this understanding, the rapid pace of changes in climate, disturbance regimes, invasive species, human population growth, and land use expected in the 21st century is likely to create substantial challenges for watershed management that may require new approaches, models, and best management practices. These challenges are likely to be complex and large scale, involving a combination of direct effects and indirect biophysical watershed responses, as well as socioeconomic impacts and feedbacks. We explore the complex relationships between forests and water in a rapidly changing environment, examine the trade-offs and conflicts between water and other resources, and examine new management approaches for sustaining water resources in the future

Climate Change and Environmental Sustainability-Volume 4

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