The variation of air and surface temperatures in London within a 1km grid using vehicle-transect and ASTER data

Urbanisation can modify the local climate, increasing the temperature of cities compared to rural areas. This phenomenon is known as the Urban Heat Island (UHI), and this paper introduces a methodology to investigate the spatial variability of air and surface temperatures across London. In particular, this study aims to investigate if a widely used spatial resolution (1 km) is appropriate for heat-related health risk studies. Data from vehicle-transect and ASTER thermal images were overlaid on a reference grid of 1 km, used by UHI simulation models. The results showed higher variability of air temperature within some specific modelled grid cells in the city centre, while surface temperatures presented higher variability in the London borders. This investigation suggests that LST has larger variation levels and more grid cells with sub-grid variation above 1°C compared to air temperature measurements

Vegetation Dynamics in Ecuador

Global forest cover has suffered a dramatic reduction during recent decades, especially in tropical regions, which is mainly due to human activities caused by enhanced population pressures. Nevertheless, forest ecosystems, especially tropical forests, play an important role in the carbon cycle functioning as carbon stocks and sinks, which is why conservation strategies are of utmost importance respective to ongoing global warming. In South America the highest deforestation rates are observed in Ecuador, but an operational surveillance system for continuous forest monitoring, along with the determination of deforestation rates and the estimation of actual carbon socks is still missing. Therefore, the present investigation provides a functional tool based on remote sensing data to monitor forest stands at local, regional and national scales. To evaluate forest cover and deforestation rates at country level satellite data was used, whereas LiDAR data was utilized to accurately estimate the Above Ground Biomass (AGB; carbon stocks) at catchment level. Furthermore, to provide a cost-effective tool for continuous forest monitoring of the most vulnerable parts, an Unmanned Aerial Vehicle (UAV) was deployed and equipped with various sensors (RBG and multispectral camera). The results showed that in Ecuador total forest cover was reduced by about 24% during the last three decades. Moreover, deforestation rates have increased with the beginning of the new century, especially in the Andean Highland and the Amazon Basin, due to enhanced population pressures and the government supported oil and mining industries, besides illegal timber extractions. The AGB stock estimations at catchment level indicated that most of the carbon is stored in natural ecosystems (forest and páramo; AGB ~98%), whereas areas affected by anthropogenic land use changes (mostly pastureland) lost nearly all their storage capacities (AGB ~2%). Furthermore, the LiDAR data permitted the detection of the forest structure, and therefore the identification of the most vulnerable parts. To monitor these areas, it could be shown that UAVs are useful, particularly when equipped with an RGB camera (AGB correlation: R² > 0.9), because multispectral images suffer saturation of the spectral bands over dense natural forest stands, which results in high overestimations. In summary, the developed operational surveillance systems respective to forest cover at different spatial scales can be implemented in Ecuador to promote conservation/ restoration strategies and to reduce the high deforestation rates. This may also mitigate future greenhouse gas emissions and guarantee functional ecosystem services for local and regional populations

Quantifying the spatio-temporal temperature dynamics of Greater London using thermal Earth observation

PhD ThesisUrban areas are highly sensitive to extreme events such as heatwaves. In order to understand how cities will respond to thermal stress it is critical to quantify not only their temporal temperature dynamics but also their spatial temperature variability. However, many cities lack weather station networks with a sufficient spatial distribution to characterise spatio-temporal intraurban temperature dynamics. One means by which spatially complete measurements of urban temperature may be derived is to employ satellite thermal Earth observed data. While some success has been achieved in understanding the temperature characteristics of cities using such data, relatively little work has been undertaken on establishing the use of long time-series Earth observed data as a supplement or alternative to screen-level air temperatures frequently utilised in urban climatological studies. In this thesis a software framework, centred around the use of a spatial database, is developed which can be used to gain an improved understanding of how satellite thermal Earth observed data can be used in the long timeseries analysis of urban temperature dynamics. The utility of the system is demonstrated by processing a 23 year time series (1985-2008) of 1,141 Advanced Very High Resolution Radiometer (AVHRR) images and hourly United Kingdom (UK) Met Office weather station measurements for the Greater London area. London was selected as the region of interest as it is the UK’s only megacity, and has been shown to exhibit both a significant urban heat island and a severe increase in population mortality during previous heatwave events. The software framework was employed to conduct two inter-related sets of analysis. First, the relationship over time between AVHRR estimated surface temperature (EST) and screen-level air temperature records is investigated and quantified. The resulting relationships are then used to produce an empirical model that can predict spatially complete summer-season air temperi atures for London. Cross-validation testing of the model at selected London weather stations showed model root mean square error (RMSE) ranging from 2.70 to 2.94°C and absolute errors in air temperature estimation of 0.45 to 1.67°C. A key finding of the thesis is that the minimal variation in prediction error between the different stations indicate a level of spatial robustness in the model across the urban surface, that is within the limits of the AVHRR EST precision. In addition, the model was used to estimate spatially averaged air temperatures over the Greater London area for selected summers, and showed a maximum error in air temperature prediction of 1.44°C. Furthermore, the prediction error for the heatwave summer of 2003 was 0.51°C, suggesting that such a model can successfully be used to estimate air temperatures for extreme heatwave summers. Such predictions are directly relevant to future assessments of urban population exposure to heatwaves, and it is envisaged that they could be used in conjunction with a population vulnerability index to create a spatially complete heatwave risk map for London. This work is then extended to investigate the utility of satellite estimated surface temperature measurements to characterise temporally and spatially intra-urban heatwave dynamics using the commonly employed urban heat island intensity metric (UHII). Analysis of the AVHRR EST found that the data are highly sensitive to local meteorological conditions, and that temporal aggregation at the monthly scale is required to provide robust data-sets for inter-year analysis of summer temperatures and generation of the UHII metric. Statistical testing of EST and air-temperature derived UHII for the heatwave summer of 2003 against other non-heatwave summers showed no significant increase in intensity at the 95% confidence level. This raises questions as to the applicability of the UHII metric to capture increases in urban temperatures during a heatwave event.Engineering and Physical Sciences Research Council and the School of Civil Engineering and Geoscience

The Effect of Land Cover on the Air and Surface Urban Heat Island of a Desert Oasis

Cities often experience a distinct climate compared to the surrounding area characterized by differences in air temperature, humidity, wind speed and direction, and amount of precipitation. Thus far, research on the urban heat island (UHI) effect has focused on cool temperate, Mediterranean and tropical climatic regions, whereas less attention has been given to the study of arid regions where the daytime surface temperature can be extremely high. This study concerns the Al Ahsa oasis, Saudi Arabia, which is a rapidly developing urban centre in an arid region. The aim of this study is to analyze the effect of land cover on the urban and sub-urban environment using ground data and multi-scale and multi-temporal satellite thermal imagery. Land surface temperatures derived from satellite thermal imagery are compared with observations from ground-based fixed and mobile temperature and relative humidity logging stations for periods in February and July. Thermal radiometers from different sensors, Landsat 7 ETM+ and MODIS, were used to measure the outgoing radiation budget at specific locations within the urban landscape. Fieldwork was undertaken contemporary with satellite overpasses to measure the diurnal air temperatures and relative humidity across different land cover types including agriculture, urban, water, exposed rock surfaces, sabkha and sand dunes. These data provide the most complete experiment so far conducted to test and refine models of the thermal radiation budget of the arid zone at the sub-city scale. The findings of this study have emphasized the effectiveness of combining the two methods, ground and satellite data, to investigate the relationship between land cover and UHI intensity. Results reveal a significant relationship between UHI spatial distribution and land cover using the two methods: mobile traverses and remote sensing. The UHI intensity is higher during the summer than the winter and at night-time than in the day. The highest UHI intensity, (10.5 °C), is located over the two major cities in the oasis (Al Hufuf and Al Mubarraz) while the lowest temperatures (- 6.4 °C below UHI), are recorded in the small villages and vegetated areas during summer at night. The outcome of this thesis will help future urban development and planning projects and provide a framework for implementing rules and regulations by local government agencies for a sustainable urban development approach

The effect of spatial settlement patterns on urban climatology

Increasing urbanization, in addition to driving climate change and pollution, can have a profound effect on the ecosystem properties within and even far from urban areas. As such, it is important to understand the energy balance of cities including the extent of its modification by urban form. This PhD thesis examines the effect of spatial settlement pattern on urban climatology. The initial study focussed on UK overpasses of the Moderate Resolution Imaging Spectro-radiometer (MODIS) satellite instrument, covering the period between 2000 and 2017, were sampled to examine the seasonal (winter and summer) night-time clear-sky upwelling long-wave energy for 35 UK cities. Total (area-summed) emitted energy was calculated per city. Well-defined (R2≥0.79) and robust ‘allometric’ scaling against city population was found for all samples. Total night-time emitted energy is found to scale sub-linearly with population on both summer and winter nights, with slope of 0.85±0.03. The scaling of night-time emitted energy with urban areas is close to linear (1.0±0.05). This indicates that UK Cities, although often appearing superficially very different, are similar in their gross thermal properties, i.e., in terms of the components of urban form, which dictate thermal properties. A case study of Nigeria’s cities on allometric scaling of emitted energy with population is also investigated, and it turned out to be very different from the UK study with slope of 0.41±0.05. Nigerian cities show much more sub-linear allometric scaling of total emitted energy with population, indicating slightly economy of scale in terms of nocturnal heat production. Local climate zones are further used to interpret results from the study. The study went further to investigate how the sum measure of the spatial distribution of emitted energy inside the city’s boundary is affected by the urban morphology, using the previous UK study. A fitted distribution of both extremes’ percentiles of emitted energy and land use maps within city were used as basis for comparison across cities in order to delineate the hottest and coldest spots in the distribution of long-wave energy for a sample night

Doctor of Philosophy

dissertationUnderstanding the spatially and temporally variant phenological responses and cycles can greatly assist the administrative planning, policy making and management in grazing, planting, and ecosystem conservation. The linkages of analysis as a basis for management have received increasing attention in the context of climate change. This research focuses on analyzing phenological responses of vegetation as constrained and moderated by environmental factors, such as landscape and season, in the geographically diverse Upper Colorado River Basin (UCRB). Due to the geographic diversity of phenological forcing in the UCRB, several homogeneous phenological subregions (phenoregions) are delineated, and the phenological responses of vegetation are analyzed on a per phenoregion basis. A multivariate adaptive regression splines (MARS) approach is adopted to model and interpret the regionally and seasonally specific relationships between environmental drivers (temperature, precipitation and solar radiant energy) and vegetation abundance, indicated by a Vegetation Index (VI). Short-term predictions of vegetation abundance are made using the models. Taking into consideration the scale of the study area and the time-step of the models, 1 km 7-day interval eMODIS data and the 1 km NASA AMES Ecocast data are used to articulate the dependent and independent variables. The series of models are integrated into a prototype phenological Decision Support System (DSS) to provide predicted vegetation abundance over the growing season and the trends of climatic variables leading to potential grazing management strategies. The implementation of the DSS is a unique attempt to integrate phenological theory and GIS technology, the combination of which makes this DSS analytically-based, intuitive and more user-friendly

Proceedings of the 6th International Workshop of the EARSeL Special Interest Group on Forest Fires Advances in Remote Sensing and GIS Applications in Forest Fire Management Towards an Operational Use of Remote Sensing in Forest Fire Management

During the last two decades, interest in forest fire research has grown steadily, as more and more local and global impacts of burning are being identified. The definition of fire regimes as well as the identification of factors explaining spatial and temporal variations in these fire characteristics are recently hot fields of research. Changes in these fire regimes have important social and ecological implications. Whether these changes are mainly caused by land use or climate warming, greater efforts are demanded to manage forest fires at different temporal and spatial scales. The European Association of Remote Sensing Laboratories (EARSeL)’s Special Interest Group (SIG) on Forest Fires was created in 1995, following the initiative of several researchers studying Mediterranean fires in Europe. It has promoted five technical meetings and several specialised publications since then, and represents one of the most active groups within the EARSeL. The SIG has tried to foster interaction among scientists and managers who are interested in using remote sensing data and techniques to improve the traditional methods of fire risk estimation and the assessment of fire effect. The aim of the 6th international workshop is to analyze the operational use of remote sensing in forest fire management, bringing together scientists and fire managers to promote the development of methods that may better serve the operational community. This idea clearly links with international programmes of a similar scope, such as the Global Monitoring for Environment and Security (GMES) and the Global Observation of Forest Cover/Land Dynamics (GOFC-GOLD) who, together with the Joint Research Center of the European Union sponsor this event. Finally, I would like to thank the local organisers for the considerable lengths they have gone to in order to put this material together, and take care of all the details that the organization of this event requires.JRC.H.3-Global environement monitorin

Ecology of freshwater turtles and other wetland wildlife in a north-central West Virginia watershed

The goal of wetland mitigation in the United States is to achieve a no-net-loss of wetlands; however, mitigated wetlands must be monitored to ensure wetland function is comparable to natural wetlands. In this study, relationships between land use practices and freshwater turtle abundance, wetland connectivity, and heavy metal bioaccumulation were investigated. In Chapter 1, a summary of pre-restoration species abundance and diversity is provided for anurans, birds, benthic macroinvertebrates, fishes, small mammals, plants, and turtles in riparian wetlands along Ruby Run, a tributary of Deckers Creek in north-central West Virginia, USA. These data provide a baseline for comparison after mitigation is completed to monitor effectiveness of achieving near-natural wetland function. In Chapter 2, relationships between relative abundance of two common turtle species found in West Virginia (snapping turtles [Chelydra serpentina] and painted turtles [Chrysemys picta]) and habitat characteristics are investigated across 39 wetlands within the Upper Deckers Creek watershed in north-central West Virginia, USA. The effects of wetland and landscape characteristics on snapping turtle movement among wetlands are also assessed. Out of the 42 adult snapping turtles across 22 wetland sites (0.04–7.45 ha) that were equipped with radio transmitters, movement was documented among wetlands for 27 individuals (66%). Wetland perimeter, substrate depth, vegetative cover, and distance from roads were positively associated with snapping turtle relative abundance. Wetland perimeter and agriculture within 500 m were negatively associated with snapping turtle movement. Wetland vegetative cover and canopy cover were positively associated with painted turtle relative abundance. Landscape-level characteristics such as nearby farm ponds, wetlands, agriculture, and roads should be considered when developing wetland conservation plans to maximize turtle abundance. Wetland connectivity is important because snapping turtles and painted turtles regularly use a diversity of wetland types with abundant vegetation and natural surroundings. In Chapter 3, the presence of cadmium, chromium, lead, mercury, selenium, and zinc concentrations is reported across sites within the Upper Deckers Creek watershed and relate landscape characteristics to concentrations found in wetland soil and turtle tissues. A total of 33 painted turtles and 24 snapping turtles across 22 sites were tested for metal concentrations through non-destructive tissue sampling (i.e. blood and nails). All metal concentrations were higher in nails than blood, but concentration differences between species varied across metals. Selenium levels in soil and turtle nails were positively correlated with proximity to mine land. Turtle nail lead concentrations were positively correlated with wetland soil Pb concentrations. Percent agriculture within 30 m of wetlands was negatively correlated with mercury in blood but positively correlated in nails, and all samples analyzed had mercury levels that exceeded U.S. Environmental Protection Agency consumption limits. Proximity to these land use practices should be considered when implementing and managing wetlands and associated buffer areas. Guidelines for turtle consumption limits should be investigated further to ensure human health and safety

Forest landscapes and global change. New frontiers in management, conservation and restoration. Proceedings of the IUFRO Landscape Ecology Working Group International Conference

This volume contains the contributions of numerous participants at the IUFRO Landscape Ecology Working Group International Conference, which took place in Bragança, Portugal, from 21 to 24 of September 2010. The conference was dedicated to the theme Forest Landscapes and Global Change - New Frontiers in Management, Conservation and Restoration. The 128 papers included in this book follow the structure and topics of the conference. Sections 1 to 8 include papers relative to presentations in 18 thematic oral and two poster sessions. Section 9 is devoted to a wide-range of landscape ecology fields covered in the 12 symposia of the conference. The Proceedings of the IUFRO Landscape Ecology Working Group International Conference register the growth of scientific interest in forest landscape patterns and processes, and the recognition of the role of landscape ecology in the advancement of science and management, particularly within the context of emerging physical, social and political drivers of change, which influence forest systems and the services they provide. We believe that these papers, together with the presentations and debate which took place during the IUFRO Landscape Ecology Working Group International Conference – Bragança 2010, will definitively contribute to the advancement of landscape ecology and science in general. For their additional effort and commitment, we thank all the participants in the conference for leaving this record of their work, thoughts and science

Foraging ecology and conservation of honeybees, bumble bees and solitary bees

This thesis contributes to two inter-related fields of research: bee conservation and bee foraging ecology. The first focuses on solitary bee ecology, identifying forage and habitat requirements along with educating the general public on aspects of solitary bee behaviour to aid in the conservation of the studied species. These results greatly improve our understanding of two rare and understudied species of solitary bee in the UK, Eucera longicornis, the long-horned bee, and Anthophora retusa, the flower potter bee, along with information on the forage requirements of a common and non-native bee species, Colletes hederae, the ivy bee, confirming its specialisation and reliance on the plant species Hedera helix, common ivy. The information provided by this research on the two rare species is currently being used by stakeholders to help conserve populations found on their land. The second focuses on how an important but understudied environmental factor, wind, influences bee foraging behaviour. Two types of common social bees, honey bees and bumblebees, that are major pollinators were studied foraging on both artificial and natural flowers, with implications for increasing our understanding of the potential future impacts of climate change on bees. Among other things, the wind research has identified a novel part of foraging behaviour much influenced by wind, hesitancy to take-off from flowers, which increases at higher wind speeds, and results in significant decreases in flower visitation rate. This thesis has contributed novel knowledge to our understanding of the foraging ecology of two rare bee species in the UK and has identified that having a wide foraging breadth does not necessarily mean a species will be common, as was found to the case for A. retsua. Foraging behaviour was also found to be influenced by the understudied environmental variable, wind, with it being found to reduce the foraging efficiency of honey bees and increase both honey bees and bumble bees hesitancy to take off. Chapter Two studied the population of the rare solitary bee, Anthophora retusa, living at Seaford Head in Sussex, one of the 5 sites it is known from in Britain. Results showed that it forages on a range of flower species, including the very common Glechoma hederacea (ground ivy). The population is small (male population size in 2019 was estimated to be around 160 individuals). Transect surveys showed that the species is restricted to a very small area, c. 30ha area within the Seaford Head reserve. Chapter Three shows that the two populations of the rare Eucera longicornis found on Gatwick Airport land had estimated populations of 300 females and 130 males in 2019, and that these populations remained approximately stable over the three years of data collection. Eucera longicornis females collected pollen predominantly from species within the Fabaceae family, which were highly abundant within the 500m surrounding the aggregations and hence are likely to be key to their success. Chapter Four confirmed that ivy, Hedera helix is the predominant floral resource for the solitary bee, Colletes hederae (ivy bee) in Sussex, with ivy comprising 98% of pollen samples collected from females. Female C. hederae activity was synchronised with ivy bloom. However, C. hederae females did collect pollen from other plant species before ivy was in peak bloom. C. hederae was the most abundant species foraging on ivy, even when honeybee hives were present in the local area. Chapter Five used artificial flowers and wind generated by fans and found that increasing wind speed caused a significant reduction (37%) in flower visits for foraging Apis mellifera. This reduction was due to an increase in ‘hesitancy’, the time to take off from a flower once a bee had finished probing. The indirect effect of flower movement had no effect on flower visitation rate. However, it did cause an increase in flight duration but this was offset by a decrease in search time once a bee was on a flower. Chapter Six found that when foraging on natural flowers of lavender and marjoram Apis mellifera flower visit rate decreased with increasing wind speed due to an increase in handling time per flower. The influence of wind speed on flower visit rate differed between lavender and marjoram, with a sharper reduction when foraging on marjoram. This was not explained by differences in flower movement speed, with flower movement not influencing flower visit rate. Chapter Seven found that when foraging on lavender, Apis mellifera flower visit rate decreased with wind speed, whereas Bombus species flower visit rate was unaffected. However, both species did experience an increase in handling time per flower with increasing wind speed. Also, the number of Bombus foragers on a patch with wind was significantly lower than on a patch where no wind was present, indicating when given the option they will choose to forage in lower wind speeds. Chapter Eight identified that hesitancy to take off increased with wind speed for both Apis mellifera and Bombus species when foraging on seven plant species in naturally varying wind conditions. Hesitancy duration in relation to wind speed did not differ between plant species. However, independently of wind speed it did. Bombus hesitancy was found to increase significantly more with increasing flower movement when compared to A. mellifera