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Among the critical global crises curbing world development and sustainability, air quality degradation has been a long-lasting and increasingly urgent one and it has been sufficiently proven to pose severe threats to human health and social welfare. A higher level of model prediction accuracy can play a fundamental role in air quality assessment and enhancing human well-being. In this paper, four types of machine learning models—random forest model, ridge regression model, support vector machine model, extremely randomized trees model—were adopted to predict PM2.5 concentration in ten cities in the Jing-Jin-Ji region of north China based on multi-sources spatiotemporal data including air quality and meteorological data in time series. Data were fed into the model by using the rolling prediction method which is proven to improve prediction accuracy in our experiments. Lastly, the comparative experiments show that at the city level, RF and ExtraTrees models have better predictive results with lower mean absolute error (MAE), root mean square error (RMSE), and higher index of agreement (IA) compared to other selected models. For seasonality, level four models all have the best prediction performances in winter time and the worst in summer time, and RF models have the best prediction performance with the IA ranging from 0.93 to 0.98 with an MAE of 5.91 to 11.68 μg/m3. Consequently, the demonstration of how each model performs differently in each city and each season is expected to shed light on environmental policy implications. [ABSTRACT FROM AUTHOR]

Cities have become a major source of greenhouse gas (GHG) emissions and controlling urban GHG emissions is a critical response to global climate change. Many previous studies on urban GHG emissions focused on inventories, changes and impact factors but few investigated the distribution of spatial sources within a city. Although inventories of a city can give information of GHG emissions from different sectors, urban government and planners need to know where emissions occur and how (or why) they occur where they do. It is thus important to spatially apportion GHG emission within a city for the practical application of GHG emission management and policies. In this study, we develop a framework for the spatial apportionment of urban GHG emissions. Xiamen is taken as a typical rapidly urbanizing city in China to demonstrate the framework of spatial apportionment. Results show that the ranking of GHG emission intensity for different land-use types of the city is manufacturing, mining, warehouse land, service industry land, transportation land, residential land and agriculture land with a ratio of 89:54:23:14:1. The vast majority of land for GHG sequestration was located in the peripheral area of the city and most land-use types in the central region of Xiamen had high GHG emissions. The implication for low-carbon urban planning is then discussed in terms of structure and connection strategies. Integrated with socioeconomic factors and urban land-use distribution, the spatial apportionment of GHG emission inventory can provide a more accurate analysis of emission sources and better management of emission sources through urban planning. [ABSTRACT FROM AUTHOR]

Due to rapid urbanization and increasing energy consumption, human society poses increasing pressure on the surrounding ecosystems that it depends on. As a result, evaluation of urban development should view cities as complex ecosystems including human and natural elements. This paper establishes a carbon balance index (CBI) for an urban ecosystem based on its socio-economic development and land use and land cover change in Xiamen, a rapidly urbanizing coastal city in southeast China. Dynamic changes in CBI can quantitatively indicate the sustainability of the urbanization process from a carbon cycling perspective. Results show that Xiamen's carbon balance condition experienced three stages: the period 1987–2002 where CBI decreased slightly, 1992–2002 where CBI moderately increased from 1.4 to 4.2, and 2003–2011 where CBI rapidly increased from 5.2 to 17.3. The carbon imbalance increased with the expansion of urban scale and urbanization. By stepwise multiple regression analysis, it was found that the main influencing factors of CBI are urbanization rate, industrial coal consumption, length of roadway network and forest area, and city managers should take these factors into consideration to achieve low-carbon city development. Finally, the CBI for the year 2030 is predicted based on CO2emissions and sequestration scenarios. [ABSTRACT FROM AUTHOR]

Since there is an increasing demand for integrating landscape ecology and urban planning theories to study complex urban ecosystems and establish rational and ecological urban planning, we introduced a new concept-urban functional landscapes which can be reclassified based on detailed land use data to fulfill the various urban functions, such as residential, commercial, industrial, and infrastructure purposes. In this paper, urban functional landscapes were defined based on urban land use data produced from Pleiades images, and then landscape metrics and population density were combined to identify the urban functional zones along an urban–rural gradient. The features of urban functional landscape patterns and population density were also analyzed, and their relationship has been explored. The results showed that the pattern of urban functional landscapes and population density in the urban functional zones (Urban center, Urban peripheral area, Landscape barrier, Satellite city and Far-suburb) along the urban–rural gradient in Xiamen doesn't totally conform to the classical theories in spatial and social aspects. Urban functional landscapes is potential of acting as bridges between the landscape ecology and urban planning theories, providing scientific support for rational urban landscape planning and urban land use policy making. [ABSTRACT FROM AUTHOR]

The ecological indicator system (EIS) is widely used. It is vital to develop a scientific and rational EIS for practical application. Assessment of an EIS's effectiveness is important to understand the gaps between practical indicators and indicators that are considered theoretically ideal. In this paper we develop a conceptual method to quantitatively assess the effectiveness of a practical EIS by comparing it with the ideal EIS that is considered perfect by using three assessment indices: linkage, coverage and representation degrees. Linkage degree reveals the relevance of individual indicators to the ideal system. Coverage degree shows the integrity of the practical indicator system compared with the ideal system. Representation degree is the ultimate goal of the quantitative assessment and can detect the gap and overlap between the practical indicator system and the ideal one. Case study on the Ecological Province Construction Indicators (EPCI) proved that our conceptual method is useful to assess the effectiveness of a practical EIS. Compared with an ideal EIS, the EPCI has a high linkage and coverage degree but biased representation. Although the practical EIS covers most of the objectives detailed in the Fujian eco-province construction documents, many social development indicators are overlooked, including ecological culture and green consumption. Using the quantitative method will improve the practical application of an EIS by detecting its redundancy and weakness. [ABSTRACT FROM AUTHOR]

Food supply and consumption are critical for sustaining urban system functions, and are key determinants of the quantity and pathways of nutrient flow in cities. Nutrient elements from urban food consumption are becoming major pollutant sources in urban environments. Therefore, understanding flow magnitude and pathways, the role of a growing population, and changing dietary structure and technology in future nutrient metabolism are essential to understand cities as ecosystems and urban environmental management. Taking the city of Xiamen, a rapid urbanizing area of Southeast China as a case study, we simulated urban metabolism of three major food-sourced nutrient elements (carbon, nitrogen, and phosphorus or CNP) over 1991–2010 and environmental emissions. Impacts of future population growth, dietary habit change, and waste treatment improvement on various environments were forecast by scenario analysis. A sensitivity analysis was conducted to test how different waste treatment technologies affect environmental emissions from food-sourced nutrients. Our results show that the food-sourced CNP had various metabolic fluxes through urban systems, with carbon mostly emitted into the air and nitrogen and phosphorus mostly discharged into landfills and water. Population growth and dietary structure change will accelerate increases of nutrient emissions to the environment, whereas enhancing current waste treatment technology can just alter emissions to different environments. Based on the results, we discuss how food-sourced nutrient metabolism can be better managed, to enhance connectivity between cities and their hinterlands and maintain environmental emissions within the carrying capacity of the cities. [ABSTRACT FROM AUTHOR]