Urban expansion and ecological pattern evolution of coastal zone in Jiangdong New District of Haikou City in the past 30 years

Based on GIS and RS technology, this paper introduces the relative resistance factors of different land grades to build the urban expansion ecological resistance surface model（UEER） on the basis of the minimum cumulative resistance model（MCR）. What′s more, combined with the hydrological analysis model, using the multi temporal research method, this paper makes a dynamic simulation analysis on the expansion pattern of construction land in 1988, 2001, 2009, 2017 and 2019 of Jiangdong New District in Haikou, and then discusses the trend of urban expansion and ecological pattern evolution in the coastal zone of Jiangdong New District in Haikou from the perspective of ecological security. The results show that:（1） Before 2018, the key construction areas in the study area showed a "pie spreading" pattern, but the area of the key construction areas in the study time domain increased from 49.48 km~2 to 61.57 km~2. Generally, the construction land is gradually concentrated, showing a trend of outward expansion centered on important transportation hubs, existing residential areas and commercial areas.（2） Urban expansion is carried out along the suitable expansion path of construction land. Because it is subject to the ecological isolation zone and is not directly connected with adjacent construction land, the "suitable expansion path" guides the optimal development of construction land to avoid blind outward expansion of construction land. In addition, the ecological isolation zone gradually infiltrates into the construction land, breaking the expansion trend of centralized and contiguous areas of construction land suitability.（3） Because Dongzhaigang Mangrove is listed as a National Nature Reserve, the sheet area formed by Dongzhaigang Mangrove Nature Reserve on the east coast of Jiangdong New District is the core area of ecological security. Although the ecological risk in the study area has been reduced to a certain extent with the support of relevant policies, it should still be paid attention to and protected.（4） Combined with the actual development of the study area, the expansion of construction land in the study area is greatly affected by policy factors. The proportion of the existing construction land in the prohibited construction area and ecological restoration area in the total construction area of the study area has increased from 0.30% to 15.65%, indicating that although the construction land in the coastal zone and its vicinity has a trend of evoluti