Analysis Of Urban Expansion Characteristics And Evaluation Of Ecological Environment Quality In The Guangdong-Hong Kong-Macao Greater Bay Area

Guangdong-Hong Kong-Macao greater bay area is one of the world’s four greater bay area urban agglomerations to be constructed in China,which will play an important role in "One Belt And One Road" economic zone.When making development plan of huge urban agglomeration like the Guangdong-Hong Kong-Macao greater bay area,it is important to make use of the advanced theory and method of urban planning together with the latest 3S integration technologies to reveal the spatiotemporal variation law of urban expansion pattern and characteristics,and to analyze the impact of urban expansion on ecological environment for the decision making of the future urban agglomeration planning and development.In this paper,Guangdong-Hong Kong-Macao greater bay area was selected as study area,and collects Landsat remote sensing image data,land use classification data and statistical yearbook data for the four years of 1990,2000,2010 and 2015 in the region.And analyzing the characteristics of urban expansion,ecological environment quality,driving factors.The results of urban expansion characteristics have been obtained by using the index method of the proportion of land occupied by construction land,the intensity of urban expansion and landscape expansion index.RSEI model have been constructed based on four index factors of greenness,humidity,heat and dryness to obtain the ecological environmental quality index of the greater bay area.The analysis of driving force was used correlation coefficient and quadratic equation fitting from economic,population,construction land area and other indicators,to reveal the interaction between human activities and the natural ecological environment.The research results have shown that:(1)The characteristics of urban expansion in Guangdong-Hong Kong-Macao greater bay area.From 1990 to 2015,the growth rates of the construction land area of the cities in Guangdong-Hong Kong and Macao bay area in descending order are as follows: Foshan,Guangzhou,Dongguan,Shenzhen,Huizhou,Jiangmen,Zhongshan,Zhuhai,Zhaoqing,Hong Kong and Macao,and the corresponding proportions of construction land in 2015 are 35.59%,22.37%,50.07%,44.73%,6.35%,8.55%,32.72%,25.64%,7.11%,19.81%and 62.19% respectively.Dongguan,Shenzhen,Zhuhai,Foshan,Zhongshan and Macao occupy more than 25% of the construction land,the intensity of expansion in these cities is reflected in the medium-speed expansion and above.Guangzhou,Huizhou,Zhaoqing,Jiangmen and Hong Kong all showed low or slow expansion.According to the summary law,the city with a larger proportion of construction land has a greater expansion intensity.From 1990 to 2015,both the filling and extension type were the main expansion modes of11 cities in the greater bay area,with less outlying distribution.The urban expansion models of Guangzhou,Dongguan,Shenzhen,Foshan and Zhongshan are dominated by filling and complemented by extension.The urban expansion models of Zhuhai,Zhaoqing,Huizhou,Jiangmen,Hong Kong and Macao are dominated by extension and complemented by filling.More than 70% of the construction land is occupied by the area occupied by forest land and cultivated land.(2)Urban ecological environment quality evaluation of Guangdong-Hong Kong-Macao greater bay area in 1990-2015 years.From a holistic perspective,the area with better ecological environment quality is 2.16 times the deteriorated area in Guangdong-Hong Kong-Macao greater bay area,indicating that the ecological environment quality of Guangdong-Hong Kong-Macao greater bay area has been greatly improved.From a regional perspective,it is clear that the ecological environmental quality of Dongguan,Zhongshan,Zhaoqing,Macao has decreased,while that of Guangzhou,Huizhou,Jiangmen and Hong Kong has increased.Shenzhen,Zhuhai and Foshan are no obvious change in ecological environment quality.In terms of the impact of urban expansion on the ecological environment,More than 70% cold spots which presenting good ecological environment are concentrated in the forest land,and about50% hot spots which representing poor ecological environment are concentrated in the construction land.Moreover,through the statistical results of the land use types in the RSEI grades,it is known that the growth of construction land will lead to expand areas of poor ecological environment,and ecological land plays a positive role in the quality of ecological environment.(3)The driving force analysis and ecological protection measures of typical cities in Guangdong-Hong Kong-Macao greater bay area.Economy and population are the main factors affecting urban expansion in Shenzhen;sewage treatment rate,industrial waste gas emissions,water conservancy-environment and public facilities management industry investment are the main factors affecting ecological environment quality.Construction land area growth,social economy and population are indirectly affecting the ecological environment quality.In response to the ecological situation of Guangdong-Hong Kong-Macao greater bay area,paper gives the following suggestions: clear problems exist;control pollution,improvement of ecological environment quality;increase of environmental protection investment,improvement of urban infrastructure construction;rational use of land resources,reduce ecological land use pressure;increase urban green space which can improve the ecological environment quality in the city center area.