Assessment Of Changes In Mangrove Forest Patterns From Multitemporal Remotely Sensed Imagery Over Zhanjiang City, Guangdong Province

As an important part of wetland ecosystems, mangrove has been protected by international biodiversity conservation organizations in recent years. While remote sensing can be a convenient alternative for monitoring mangrove protecting efforts because field investigation is very difficult and costly to conduct. In this paper, using four temporal Landsat remote sensing images dated 1977,1991,2000 and 2005, defined as 3 phases,1977-1991,1991-2000, 2000-2005, a comparative analysis of mangrove forest dynamics for Gaoqiao and Yingzai of Zhanjiang Mangrove National Nature Reserve was conducted with the assistance of the field investigation and some auxiliary data. Specifically, the mangrove extent and aquaculture extent, mangrove density, and the conversion among different land cover types were identified. Additionally, geospatial metrics and the forest fragmentation model were also applied to evaluate the trends of mangrove fragmentation. And by interviewing the local experts responsible for the management of the Reserve, the impacts of mangrove wetland landscape pattern changes over the local biodiversity were also assessed.Results suggested that due to the expansion of aquaculture activities, the mangrove area of the two case areas has undergone a process of decrease and then increase, while the mangrove suffered the most serious fragmentation status in 1991, accompanied by a lowest mangrove area and mangrove density. The dynamics of local biodiversity is consistent with the changing trends of mangrove landscapes over time, and the establishment of Zhanjiang Mangrove National Reserve has promoted the protection and restoration of mangrove in our study areas by afforestation efforts from 1991 to 2005. These results indicated that remote sensing technology is quite favorable for monitoring and assessing mangrove forest structure and dynamics, helping increase the transparency of project implementation process. Finally, the driving forces for mangrove landscape pattern changes were studied, and some regulation and control countermeasures for Zhanjiang Mangrove National Reserve were proposed according to the analyses.