As an important ecosystem type in the coastal zone, mangroves have important ecological functions, such as maintaining coastal biodiversity, preventing wind and consolidating the coast, promoting silt and building land. It is of great significance to understand the protected status of mangroves in the context of climate change and rapid urbanization. Based on the mangrove classification data from remote sensing interpretation, through vacancy analysis, the in-situ protection status of mangroves in China is analyzed. The results show that the total area of mangroves distributed in China is 264 km² (excluding the statistical data of Hong Kong, Macao and Taiwan), of which 61.4% are protected in natural reserves. In terms of the main provinces where mangroves are distributed, the mangrove area distributed in Hainan Province is small but the protection proportion is high, while the mangrove area distributed in Guangxi and Guangdong Province is large but the proportion of protected areas is relatively low. Among the three mangrove types, Rhizophora apiculate-Xylocarpus granatum and Rhizophora stylosa-Bruguiera gymnorrhiza had high proportions (>90%) covered by reserves, but relatively small areas. In contrast, Kandelia candel-Aegiceras corniculatum-Avicennia marina had relatively low reserve coverage (52.6%), but a large area. The study puts forward the key areas of mangrove distribution outside the nature reserve, and suggests that they should be protected by delimiting ecological protection red lines.

Shore line change is considered as one of the most dynamic processes, which were mapped along the coast of Tiruvallur district by using topographic maps of 1976 and multi-temporal satellite images. The satellite images pertaining to 1988, 1991, 2006, 2010, 2013 and 2016 were used to extract the shorelines. It is important to map and monitor the HTL (High Tide Line) at frequent time intervals as the shoreline was demarcated by using visual interpretation technique from satellite images and topographic maps. Followed by this, an overlay analysis was performed to calculate areas of erosion and accretion in the study area. The results revealed that the coast of Tiruvallur district lost 603 ha and gained 630 ha due to erosion and accretion respectively. It was confirmed after the ground truth survey carried out in the study area. The high accretion of 178 ha was found nearby Pulicat Lake and low accretion of 19 ha was seen between Pulicat Lake and Kattupali Port. The high erosion area was found along the Pulicat Lake, Kattupali and Ennore ports, and Ennore creek mouth and southern Ennore such as Periya Kuppam, Chinna Kuppam, Kasi Koil Kuppam, and Thyagarajapuram. It may be concluded that the coastal erosion and accretion in the study area were mainly caused by anthropogenic and natural factors, which altered the coastal environment.