Recent ecological trajectory of lake Taihu and land-use history reconstructed from lake sediment DNA

Author(s):  
Charline Giguet-Covex ◽  
Qi Lin ◽  
Ludovic Gielly ◽  
Fabien Arnaud ◽  
Ke Zhang

<p>More than 80% of shallow lake ecosystems in the Yangtze floodplain suffer significant disturbances from the 50’s, especially eutrophication. These environmental degradations and subsequent loss of services are related with the important and rapid development of the agriculture, industry, urban areas and the population boom in the region. Lake Taihu is one of the largest lakes of the floodplain and represents an important water resource (for drinking and fishing) for the population of the two big cities on the lake shore. This lake experimented two shifts toward the degradation of the trophic state: one in the 50-60’s and a second in 80’s.</p><p>In order to document the causes of these ecological shifts, we applied the DNA metabarcoding approach on lake sediments and focused on plants as proxy of land use. Whereas this proxy has been successfully applied in many lakes over the world, it has never been tested in large shallow lakes and not in China either.</p><p>We show important changes in land use in 50’s and 80’s related with agricultural developments (i.e. intensification) and urban expansion, respectively. In fact, in the 50’s crop plants are increasing (rapeseed and/or cabbage, rice and/or wheat, barley and <em>Poaceae</em>) whereas in 80’s, we record the development of several plants associated to gardens (e.g. ornamental species). Moreover, this last period is characterised by the presence of trees mostly cultivated along stream banks to protect dikes against erosion. Between the 80’s and the years 2000, the plant diversity recorded in the sediment strongly increase, which may be due to higher detrital inputs (i.e. more efficient DNA transfer). The timing in land-use changes corresponds to the main shifts in lake trophic state.</p>

2021 ◽  
Author(s):  
Eric Vaz ◽  
Lisa Bowman

Urban growth has had unprecedented consequences on environmental sustainability and anthropogenic activity. The eroding coastlines throughout the world are subject to the massive expansion of urban areas and the accountability of sustainable hinterland landscapes. The Golden Horseshoe is Canada’s fastest growing region extending from the Niagara Peninsula and one of the most active economic regions in North America. This paper adopts a combined assessment of land use change and transitions in the coastal stretches of the Greater Golden Horseshoe. Comprising the urban expansion of the region between 1990 and 2011, an integrated assessment was carried out to: (i) detect changes in coastal lines along Lake Ontario; (ii) derive land use changes along the coast through spatial accounting matrices; and (iii) integrate climate change data for a combined assessment of future erosion loci. Visible erosion was found between the decade of 1990 and 2000, while certain areas have shown coastal recession in the southern region. The maximum recession was found to be 30 m, with an increasing urban sprawl of 19.8% between 1990 and 2000. A combined temperature increase of 2 °C over the coming decades brings the increase in urban heat islands leading to the importance of combined land policies to mitigate the common problem of erosion in vulnerable urban stretches and liveability concerning spatial resilience of growing urban regions in North America.


2020 ◽  
Author(s):  
Inês Amorim Leitão ◽  
Carla Sofia Santos Ferreira ◽  
António José Dinis Ferreira

<p>Land-use changes affect the properties of ecosystems, and are typically associated with decreasing ability to supply services, which in turn causes a decrease in the social well-being. Urbanization is identified as one of the main causes of ecosystem degradation, once it is considered an artificial space that replaces natural areas.This study investigates the impact of land-use changes during 20 years (1995-2015) on the potential supply of ecosystem services in Coimbra municipality, central Portugal. The assessment was based on the evaluation performed by 31 experts familiar with the study area, through questionnaires. The experts ranked the potential supply of 31 ecosystem services, grouped in regulation, provisioning and cultural services, for the several land-uses existent. Experts performed a qualitative evaluation, considering ‘strong adverse potential’, ‘weak adverse potential’, ‘not relevant’, ‘low positive potential’ and ‘strong positive potential’. The qualitative evaluation was converted into a quantitative classification (-2, -1, 0, 1, 2). Quantitative values were then used to develop an ecosystem services quantification matrix and to map the information in the study area, using Geographic Information Systems (GIS). An urban expansion from 14% to 18% was recorded over the last 20 years. Agricultural land decreased 8% due to conversion into forest (4% increase) and urban areas (4% increase). This has led to a decrease in the supply of provision (e.g. food) and regulation services (e.g. flood regulation). In fact, over the last years, recurrent floods have been increasingly noticed in Coimbra city. On the other hand, the growth of forest areas has led to an increase in general ESs supply. The adverse impacts of urbanization were partially compensated by enlarging the benefits provided by forest areas, which is the land-use with greatest ESs potential supply. In order to support urban planning and develop sustainable cities, it is essential to quantify the potential supply of ecosystem services considering local scale and characteristics.</p>


Land ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 445 ◽  
Author(s):  
Abebe Mengaw Wubie ◽  
Walter T. de Vries ◽  
Berhanu Kefale Alemie

The contemporary urbanization and its implication to land use dynamics especially in the peri-urban areas are emerging as a cross-cutting theme in policy debates and scientific discourse. As most cities in developing countries, including Ethiopia, are experiencing continuous expansion of built-ups and dynamic land use changes, monitoring and an in-depth analysis of the past, present and future predictions of these changes are important for a holistic understanding of the problem, its consequence, and to regulate proper land use intervention options. Thus, the main objective of this research is to assess land use dynamics and processes of land intervention in the peri-urban areas of Bahir Dar city using a socio-spatial analysis. It assesses to what extent the existing peri-urban land intervention processes and land use decisions are effective in combating and controlling unwanted land use changes. Primary socio-economic data were collected using questionnaires, focus group discussions (FGDs) and key informant interviews; in addition, spatial data including Landsat and Sentinel imageries of 1993, 2001, 2011 and 2020 were utilized. Land use/land cover (LULC) classes were computed using the integration of spectral and object-based image classification techniques. The results signal that built-ups are expanding horizontally with unpredicted patterns. This is because the existing land intervention processes are lacking effectiveness to govern the spatial patterns of built-ups. The results further depict that processes of land use intervention do not only determine horizontal urban expansion but also determine the nature of people-to-land relationships, which involve both formal and informal processes. This creates haphazard, disputed and unregulated land use systems in peri-urban areas of Bahir Dar. The socio-spatial methodology applied in this research is effective in monitoring both the spatial and social dimensions of land use changes. The spatial results effectively demonstrate the dynamics of land uses; whereas, the social analysis supports understanding of the processes of land use interventions. In conclusion, monitoring processes of land use interventions are key policy and decision making directions to regulate and manage land use dynamics in the peri-urban area.


2021 ◽  
Author(s):  
Eric Vaz ◽  
Lisa Bowman

Urban growth has had unprecedented consequences on environmental sustainability and anthropogenic activity. The eroding coastlines throughout the world are subject to the massive expansion of urban areas and the accountability of sustainable hinterland landscapes. The Golden Horseshoe is Canada’s fastest growing region extending from the Niagara Peninsula and one of the most active economic regions in North America. This paper adopts a combined assessment of land use change and transitions in the coastal stretches of the Greater Golden Horseshoe. Comprising the urban expansion of the region between 1990 and 2011, an integrated assessment was carried out to: (i) detect changes in coastal lines along Lake Ontario; (ii) derive land use changes along the coast through spatial accounting matrices; and (iii) integrate climate change data for a combined assessment of future erosion loci. Visible erosion was found between the decade of 1990 and 2000, while certain areas have shown coastal recession in the southern region. The maximum recession was found to be 30 m, with an increasing urban sprawl of 19.8% between 1990 and 2000. A combined temperature increase of 2 °C over the coming decades brings the increase in urban heat islands leading to the importance of combined land policies to mitigate the common problem of erosion in vulnerable urban stretches and liveability concerning spatial resilience of growing urban regions in North America.


2020 ◽  
Vol 18 (11) ◽  
Author(s):  
Abdul Ghapar Othman ◽  
Nurul Hanisah Jizan

Urbanization is the process of transforming a characteristically rural society into an urban one. The urban population is growing at an increasing rate while the rural population is declining, giving rise to imbalances in the development between urban and rural areas. The government’s strategy is to distribute the development to the major settlement centres in the rural areas, which are experiencing the same effects of urbanization as the urban areas in terms of changes to the use of land, especially the reduction of agricultural land and the increase in built-up areas. This study used the method of overlay in GIS applications to investigate land use changes, the speed of urban expansion and direction of development that has taken place from the period 2001 to 2018 in the town of Kuala Nerang, Kedah. This town has undergone a change in its status from a main settlement centre to a district administrative centre. Agricultural lands, which were targeted for development in the rural areas, have been converted into built-up areas. The speed of urban expansion has been slow, although some areas have recorded a higher rate. The development is moving towards the west along the main road connecting the major towns in this part of the state. The functions of the district administrative centre have influenced land use changes.


2019 ◽  
Vol 11 (21) ◽  
pp. 6174 ◽  
Author(s):  
Jinming Yang ◽  
Shimei Li ◽  
Huicui Lu

The spatial structure and configuration of land-use patches, i.e., landscape patterns could affect the flow of energy and materials in inner-urban ecosystems, and hence the sustainable development of urban areas. Studying landscape pattern changes under the process of urbanization would have implicational significance to urban planning and urban sustainability. In this paper, land-use change and urban expansion intensity (UEI) were treated as the inducement factors for changes in landscape patterns, and stepwise regression and geographically weighted regression (GWR) were adapted to quantify their integrated and distributed magnitude effects on landscape patterns, respectively. The findings suggested that land-uses have different contributions to changes in landscape patterns at different urban development zones (downtown, suburban plain area and mountainous suburban areas). Furthermore, the GWR analysis results indicated that the effect of UEI on landscape patterns has spatial and temporal heterogeneity. From 1987 to 2000, the UEI had great explanatory capacity on changes in landscape patterns and helped the landscape assemble faster in the downtown and adjacent areas. However, with the shifting of the center of urban construction from downtown to the suburbs, the high explanatory ability was oriented towards suburban areas during 2000–2016 and the magnitude of influence spatially changed. Therefore, a compact city and protection policy should be adapted to different regions in the study area to achieve strong urban sustainability.


Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 312
Author(s):  
Barbara Wiatkowska ◽  
Janusz Słodczyk ◽  
Aleksandra Stokowska

Urban expansion is a dynamic and complex phenomenon, often involving adverse changes in land use and land cover (LULC). This paper uses satellite imagery from Landsat-5 TM, Landsat-8 OLI, Sentinel-2 MSI, and GIS technology to analyse LULC changes in 2000, 2005, 2010, 2015, and 2020. The research was carried out in Opole, the capital of the Opole Agglomeration (south-western Poland). Maps produced from supervised spectral classification of remote sensing data revealed that in 20 years, built-up areas have increased about 40%, mainly at the expense of agricultural land. Detection of changes in the spatial pattern of LULC showed that the highest average rate of increase in built-up areas occurred in the zone 3–6 km (11.7%) and above 6 km (10.4%) from the centre of Opole. The analysis of the increase of built-up land in relation to the decreasing population (SDG 11.3.1) has confirmed the ongoing process of demographic suburbanisation. The paper shows that satellite imagery and GIS can be a valuable tool for local authorities and planners to monitor the scale of urbanisation processes for the purpose of adapting space management procedures to the changing environment.


2021 ◽  
Vol 13 (10) ◽  
pp. 5718
Author(s):  
Changqing Sui ◽  
Wei Lu

The urban fringe, as a part of an urban spatial form, plays a considerably major role in urban expansion and shrinking. After decades of rapid development, Chinese cities have advanced from a simple expansion stage to an expansion–shrinking-coexistence stage. In urban shrinking and expansion, the urban fringe shows different characteristics and requirements for specific aspects such as urban planning, land use, urban landscape, ecological protection, and architectural form, thereby forming expanding and shrinking urban fringes. A comprehensive study of expanding and shrinking urban fringes and their patterns is theoretically significant for urban planning, land use, planning management, and ecological civilisation construction.


2020 ◽  
Vol 12 (11) ◽  
pp. 4346 ◽  
Author(s):  
Huina Wang ◽  
Lina Tang ◽  
Quanyi Qiu ◽  
Huaxiang Chen

Understanding the spatiotemporal variability of habitat quality as a function of land-use changes is important for expanding scientific knowledge of ecological conservation. In this study, the impacts of land-use change on habitat quality were assessed in two urban agglomerations in China at different stages of development, namely (1) the Yangtze River Delta Urban Agglomeration (YRDUA), which has reached the middle and late stage of urbanization, and (2) the Golden Triangle of Southern Fujian (GTSF), which has reached the middle and early stage. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) habitat quality model was applied to determine the habitat quality and the degree of habitat degradation in these two agglomerations. Overall, the habitat quality in the YRDUA was found to be clearly inferior to that in the GTSF. In the GTSF, more than 65% of the habitat was of good or excellent quality, whereas in the YRDUA, less than 45% of the habitat reached this quality. By combining the concepts of land use, landscape, and habitat, the boundary of degradation and the general increase in habitat quality from 2000 to 2015 were found to be mainly related to the landform, the dominant landscape, and the concentration of non-habitat areas. Additionally, the type, distribution, and fragmentation of the dominant habitat were shown to play important roles in habitat quality. Moreover, changes in industrial composition over time were demonstrated to be critical drivers of changes in areas of construction land.


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