Yanglin Wang

Assessing vulnerability to drought based on exposure, sensitivity and adaptive capacity: A case study in middle Inner Mongolia of China

In this paper, we proposed a framework for evaluating the performance of ecosystem strategies prepared for enhancing vulnerability reduction in the face of hazards due to climate change. The framework highlights the positive effects of human activities in the coupled human and natural system (CHANS) by introducing adaptive capacity as an evaluation criterion. A built-in regional vulnerability to a certain hazard was generated based upon interaction of three dimensions of vulnerability: exposure, sensitivity and adaptive capacity. We illustrated the application of this framework in the temperate farming-grazing transitional zone in the middle Inner Mongolia of the northern China, where drought hazard is the key threat to the CHANS. Specific indices were produced to translate such climate variance and social-economic differences into specific indicators. The results showed that the most exposed regions are the inner land areas, while counties located in the eastern part are potentially the most adaptive ones. Ordos City and Bayannur City are most frequently influenced by multiple climate variances, showing highest sensitivity. Analysis also indicated that differences in the ability to adapt to changes are the main causes of spatial differences. After depiction of the spatial differentiations and analysis of the reasons, climate zones were divided to depict the differences in facing to the drought threats. The climate zones were shown to be similar to vulnerability zones based on the quantitative structure of indexes drafted by a triangular map. Further analysis of the composition of the vulnerability index showed that the evaluation criteria were effective in validating the spatial differentiation but potentially ineffective because of their limited time scope. This research will be a demonstration of how to combine the three dimensions by quantitative methods and will thus provide a guide for government to vulnerability reduction management.

Correlations between Urbanization and Vegetation Degradation across the World’s Metropolises Using DMSP/OLS Nighttime Light Data

Changes in biodiversity owing to vegetation degradation resulting from widespread urbanization demands serious attention. However, the connection between vegetation degradation and urbanization appears to be complex and nonlinear, and deserves a series of long-term observations. On the basis of the Normalized Difference Vegetation Index (NDVI) and the image’s digital number (DN) in nighttime stable light data (NTL), we delineated the spatiotemporal relations between urbanization and vegetation degradation of different metropolises by using a simplified NTL calibration method and Theil-Sen regression. The results showed clear and noticeable spatiotemporal differences. On spatial relations, rapidly urbanized cities were found to have a high probability of vegetation degradation, but in reality, not all of them experience sharp vegetation degradation. On temporal characteristics, the degradation degree was found to vary during different periods, which may depend on different stages of urbanization and climate history. These results verify that under the scenario of a vegetation restoration effort combined with increasing demand for a high-quality urban environment, the urbanization process will not necessarily result in vegetation degradation on a large scale. The positive effects of urban vegetation restoration should be emphasized since there has been an increase in demand for improved urban environmental quality. However, slight vegetation degradation is still observed when NDVI in an urbanized area is compared with NDVI in the outside buffer. It is worthwhile to pay attention to landscape sustainability and reduce the negative urbanization effects by urban landscape planning.

Net primary productivity (NPP) dynamics and associated urbanization driving forces in metropolitan areas: a case study in Beijing City, China

ContextEco-environmental effects of urbanization are a focus in landscape ecology.ObjectiveThe influences of population, economic and spatial development during the urbanization process in Beijing City, China on net primary productivity (NPP) were analyzed. The responding mechanism of NPP in different urbanization stages was also examined to develop advice about eco-environmental sustainability of urban development.MethodsUsing the Carnegie Ames Stanford Approach model, we estimated NPP. Using linear regression and polynomial regression analysis, we analyzed NPP responses to stages of urbanization.ResultsHigh NPP areas were located in northeast Yanqing, northwest Miyun, northern Huairou and Pinggu. The distribution of NPP generally occurred in the following order from high NPP to low NPP: outer suburbs, inner suburbs, encircled city center, and inner city. Because of the heat island effect in winter, the estimated NPP in the encircled city center and inner city was higher in 2009 than in 2001. There was a negative correlation between NPP and both economic and spatial urbanization, but an increase in population did not necessarily lead to an immediate decrease in NPP. An analysis of NPP dynamics in five kinds of urban development zones showed that urbanization resulted in a lasting and observable loss of NPP over time and space, although there was some promotion of NPP in highly urbanized zones.ConclusionThere are three stages in the response of NPP to urbanization: damage stage, antagonistic stage, and coordination stage. The stage threshold depends on local eco-environmental management and urban planning interventions.

Evaluation for regional ecosystem health: methodology and research progress

Abstract The evaluation for ecosystem health is one of the hotspots in the fields of macro-ecology and ecosystem management. Conducting analysis at the regional scale is an important direction for evaluating ecosystem health. Changing the spatial scale from the local to the regional level leads to great differences in targets and methodologies for ecosystem health evaluation and creates a new direction for regional ecosystem health research. Compared with the ecosystem health at the local scale, which refers to a single ecosystem type, the regional ecosystem health focuses on the health conditions and spatial patterns of different ecosystem types. However, there has been little attention paid to this very research up to now. Based on the progress on ecosystem health studies at the regional scale, the study reported in this article aims to discuss the implications of the conception of regional ecosystem health and to put forward a methodology for evaluating the regional ecosystem health. The main results include: (1) there is a significant scaling effect on the ecosystem health analysis, and the regional level is the key scale used to focus on the correlation between spatially neighboring ecosystems in terms of ecosystem health; (2) regional ecosystem health can be defined through 4 aspects, i.e., vigor, organization, resilience, and ecosystem service functions; (3) the basic evaluation objects of the regional ecosystem health is spatial entity, which is the matrix of different ecosystem types; (4) indicator system method is the only approach to evaluate regional ecosystem health; (5) the absolute thresholds of the evaluation indicators for the regional ecosystem health do not exist; the aim of the evaluation is to discuss the temporal dynamic changes and spatial differences of health conditions rather than to ascertain whether a region is healthy or not in view of ecological sustainability; and (6) the integration of evaluation results at multispatial scales, the application of this methodology in the landscape ecology, and the utilization of geographic information systems (GIS), remote sensing (RS), and Global Positioning Systems (GPS) technologies are the main directions for further research.

Landscape spatial changes associated with rapid urbanization in Shenzhen, China

Rapid urbanization and a building boom in Chinese cities, together with the increase in human disturbances in ecosystems, have resulted in a range of ecological and land-use problems. The formulation of policies relating to urban land use requires adequate understanding of the landscape dynamics. The objective of the study was to describe spatial patterns and dynamic changes of the regional landscape of Shenzhen in the past 20 years. Based on MSS & TM images from 1978, 1986, 1990, 1995 and 1999, a landscape classification map of Shenzhen was constructed. Three kinds of spatial pattern indices, including landscape diversity, spatial configuration and characteristics of patches, as well as a human disturbance index, were examined using models and GIS. In the past two decades, the regional landscape in Shenzhen has changed dramatically, from a typical agricultural landscape to a rapidly urbanizing landscape. The gradual reduction in the cultivated land area and the dramatic increase in the built-up areas illustrate this progress clearly. Indices for the landscape spatial pattern have changed substantially. Some of the changes, reflecting the reasonable control of urban planning on the regional landscape, are the consequence of careful planning, but many of them are the result of disordered human disturbances that have occurred during the rapid urbanization process. These findings are helpful to future landscape development and land-use planning.

Evaluation for sustainable land use in coastal areas: A landscape ecological prospect

Evaluation of sustainability is the core of research on sustainable land use. To a certain extent, traditional social, economic and ecological evaluation for sustainable land use can be regarded as an appraisal on the temporal scale without evaluation of spatial patterns. Landscape ecology can help to realize spatial evaluation for sustainable land use. In this paper, we construct landscape ecological indicators for evaluating sustainable coastal land use from the aspects of landscape productivity, threats and stability, to realize a synthetic temporal-spatial evaluation. These cover the five pillars of sustainable land use, i.e. productivity, security, protection, viability and acceptability. The results of applying landscape ecological evaluation to a case study in Wudi County in China show that land use sustainability is somewhat low and there are great regional differences between its 11 villages. We classified the 11 villages into 5 grades: strong sustainable land use, sustainable land use, weak sustainable land use, weak unsustainable land use, and strong unsustainable land use. Each grade has different land use characteristics and differs in the counter-measures required. But the core countermeasures in all the grades are to improve landscape productivity, to reduce human threats and to optimize landscape patterns.

Vegetation Dynamics and Associated Driving Forces in Eastern China during 1999–2008

Vegetation is one of the most important components of the terrestrial ecosystem and, thus, monitoring the spatial and temporal dynamics of vegetation has become the key to exploring the basic process of the terrestrial ecosystem. Vegetation change studies have focused on the relationship between climatic factors and vegetation dynamics. However, correlations among the climatic factors always disturb the results. In addition, the impact of anthropogenic activities on vegetation dynamics was indeterminate. Here, vegetation dynamics in 14 provinces in Eastern China over a 10-year period was quantified to determine the driving mechanisms relating to climate and anthropogenic factors using partial correlation analysis. The results showed that from 1999 to 2008, the vegetation density increased in the whole, with spatial variations. The vegetation improvement was concentrated in the Yangtze River Delta, with the vegetation degradation concentrated in the other developed areas, such as Beijing-Tianjin-Hebei Region and the Pearl River Delta. The annual NDVI changes were mainly driven by temperature in Northeast China and the Pearl River Delta, and by precipitation in the Bohai Rim; while in the Yangtze River Delta, the driving forces of temperature and precipitation almost equaled each other. Furthermore, the impact of anthropogenic activities on vegetation dynamics had accumulative effects in the time series, and had a phase effect on the vegetation change trend.

Analyzing nonlinear variations in terrestrial vegetation in China during 1982-2012.

Quantifying the long-term trends of changes in terrestrial vegetation on a large scale is an effective method for detecting the effects of global environmental change. In view of the trend towards overall restoration and local degradation of terrestrial vegetation in China, it is necessary to pay attention to the spatial processes of vegetative restoration or degradation, as well as to clarify the temporal and spatial characteristics of vegetative growth in greater geographical detail. However, traditional linear regression analysis has some drawbacks when describing ecological processes. Combining nonparametric linear regression analysis with high-order nonlinear fitting, the temporal and spatial characteristics of terrestrial vegetative growth in China during 1982–2012 were detected using the third generation of Global Inventory Modeling and Mapping Studies (GIMMS3g) dataset. The results showed that high-order curves could be effective. The region joining Ordos City and Shaanxi Gansu Ningxia on the Loess Plateau may have experienced restoration–degradation–restoration processes of vegetative growth. In the Daloushan Mountains, degradation–restoration processes of vegetative growth may have occurred, and the occurrence of several hidden vegetative growth processes was located in different regions of eastern China. Changes in cultivated vegetation were inconsistent with changes in other vegetation types. In southern China and some high-altitude areas, temperature was the primary driver of vegetative growth on an interannual scale, while in the north, the effect of rainfall was more significant. Nevertheless, the influence of climate on vegetation activity in large urban areas was weak. The trend types of degradation–restoration processes in several regions were inconsistent with the implements of regional land development and protection strategy. Thus, the role of human activity cannot be ignored. In future studies, it will be still necessary to quantify the effects of human management on spatial patterns, develop trend-fitting methods, and explore more refined methods of analyzing the driving forces affecting large-scale changes in vegetative growth.

Diversification of Land Surface Temperature Change under Urban Landscape Renewal: A Case Study in the Main City of Shenzhen, China

Unprecedented rapid urbanization in China during the past several decades has been accompanied by extensive urban landscape renewal, which has increased the urban thermal environmental risk. However, landscape change is a sufficient but not necessary condition for land surface temperature (LST) variation. Many studies have merely highlighted the correlation between landscape pattern and LST, while neglecting to comprehensively present the spatiotemporal diversification of LST change under urban landscape renewal. Taking the main city of Shenzhen as a case study area, this study tracked the landscape renewal and LST variation for the period 1987–2015 using 49 Landsat images. A decision tree algorithm suitable for fast landscape type interpretation was developed to map the landscape renewal. Analytical tools that identified hot-cold spots, the gravity center, and transect of LST movement were adopted to identify LST changes. The results showed that the spatial variation of LST was not completely consistent with landscape change. The transformation from Green landscape to Grey landscape usually increased the LST within a median of 0.2 °C, while the reverse transformation did not obviously decrease the LST (the median was nearly 0 °C). The median of LST change from Blue landscape to Grey landscape was 1.0 °C, corresponding to 0.5 °C in the reverse transformation. The imbalance of LST change between the loss and gain of Green or Blue landscape indicates the importance of protecting natural space, where the benefits in terms of temperature mitigation cannot be completely substituted by reverse transformation.

Identification of multiple climatic extremes in metropolis: a comparison of Guangzhou and Shenzhen, China

Identifying historical trends in the integrated frequencies of various climate extremes is meaningful in climatic hazard research. However, the variation trends in regional climate extremes still need to be described by more effective indices, correlations among multiple climatic extremes and different regions need to be quantified, and the urban heat island backgrounds and thermal bioclimate conditions in which people live need to be noted. In this study, the threats of heat wave, heavy rain, strong wind, and Universal Thermal Climate Index (UTCI) stress were identified both by units of days using the 90th percentile threshold, and by an unscaled magnitude index derived from kernel density functions for Guangzhou and Shenzhen, China, in 1960–2013. The results show that both metropolises experienced an increase in heat wave threat and a decrease in strong wind threat, and the change amplitudes were higher for Guangzhou than Shenzhen. The correlation of heat wave threat between the two metropolises was significant, while the other correlations depended on the city and index. The heat wave threat was correlated with the UTCI stress in Guangzhou, while both heat wave threat and UTCI stress were correlated with strong wind threat in Shenzhen. The UTCI stress indicated that bioclimate conditions for human habitat have not deteriorated, especially in Shenzhen. In the daily-level results, the heat waves had close relationship between the two adjacent cities, and people suffered from hazard events were usually in high weighted indices of extremes.