Change of wetland landscape patterns and its driving factors in Pearl River Delta urban agglomeration

Wetland ecosystem is an important part of urban ecological security system. Pearl River Delta (PRD) urban agglomeration was used as a research area, and the spatial and temporal distribution of wetland resources in the area was investigated using multi-period remote sensing data. At the same time, the changes of wetland structure and landscape pattern were analyzed combined with GIS technology, and eight driving factors were selected for principal component analysis to explore the causes of dynamic changes of wetland landscape in the background of rapid urbanization. The results showed that the main wetland types in PRD urban agglomeration were paddy fields, followed by reservoirs, ponds and canals, and the distribution area of lakes, beaches and marshes was relatively small. From 2000 to 2015, the wetland area of PRD urban agglomeration had been lost, with a total loss of 1 613 km², of which the most serious loss occurred during 2000-2005, and then the damage trend gradually slowed down; the sum of the wetland loss areas in Foshan, Guangzhou, Zhongshan and Huizhou accounted for about 77% of the total loss area. Through the study of the spatio-temporal conversion of wetlands, it was found that human activities had a far-reaching impact on wetland conversion in the past 15 years, mainly manifested in the occupation of wetlands in construction land, the transfer of paddy fields to reservoir/ponds, and the reclamation of beaches into paddy fields. The study of landscape index showed that paddy fields and canals were the dominant landscape types in PRD, with high degree of aggregation, while the spatial distribution of other wetland types tended to be discrete. It was found that human activities were the main factors affecting the wetland landscape pattern changes, and urban expansion was the main pathways of encroachment on wetlands. In addition, the wetland landscape was also influenced by the policies and climate.