Coastal Reclamation Impacts On Carbon Storage In China's Coastal Wetland

Coastal wetlands are characterized with high net primary production and slow rates of organic matter decomposition,which play an essential role in mitigating climate change in coastal area.Due to the rapid population growth and urbanization in coastal area,coastal area are exposed to intensive reclamation activities,which leads to serious degradation in China's coastal wetland.It is of great practical and academic value to evaluate reclamation impacts on carbon storage in coastal wetland,which may contribute to optimize reclamation activities management,as well as formulate wetland conservation action plan and climate mitigation strategies.In this study,the carbon density values were collected from the literatures.We estimated the carbon storage of different land use types in China's reclamation area for 2015 using In VEST model.In addition,we analyzed reclamation impacts on land use pattern and carbon storage in coastal wetland,as well as in coastal nature protected area from 1990 to 2015.The critical findings include:(1)Carbon density value collection:carbon density of different land use types in various coastal areas was collected from a large number of literatures.The carbon density in three different study areas(northern,middle and southern coastal areas)are ranged from 1.22 to 27.71 kg/m2.(2)Assessment of land use pattern and carbon storage distribution in reclamation areas:land use types in China's reclamation area were dominated by artificial wetlands(salt pan and aquatic agriculture),followed by unused land(such as salina land,bared land,new water,etc.)and construction land.The area of reclamation showed a continuous growth trend from 1990 to 2015,which reflects that China's coastal areas have experienced high-intensity reclamation in recent years.The total carbon storage in the reclamation area was 38.24 Tg(average 40.37 Mg/ha).At a regional scale,the order of carbon storage per unit area is:middle coastal area>northern coastal area>southern coastal area,Yangtze River Delta>Bohai Bay>Pearl River Delta.(3)Estimation of reclamation impact on land use pattern and carbon storage in coastal wetland:More than 380,000 hectares coastal wetland was under influences of reclamation,accounting for 6.67%of the total area of China's coastal wetland.There were 36.65 Tg and 15.96 Tg carbon stored in the coastal wetland located in reclamation area in 1990 and 2015 respectively,with 20.69 Tg carbon storage loss.The land use transfer matrix of coastal wetland showed that the decrease of natural wetland was the main reason for carbon storage loss.The carbon storage of natural wetland decreased greatly within last 25 years,however,a small increase of carbon storage in the artificial wetland was observed due to land use changes.This thesis also estimated the carbon emissions of energy consumption in China's reclamation area in 2014.The results show that the average annual carbon emissions generated by land use change(reclamation)was approximately accounting for 6.18%carbon emissions of the energy consumption in China's coastal reclamation area in 2014.(4)Impacts of reclamation activities on coastal nature protected area:About 103,100 hectares coastal nature protected area was under influences of reclamation,accounting for 5.73%of the total area.The land use type was dominated by artificial wetlands,followed by natural wetlands,cultivated land,construction land and unused land.The natural wetland loss mostly appeared in Yancheng Rare Birds,Shuangtai Estuary,Dalian National Spotted Seal(Phoca vitulina)Nature Reserve and other National Nature Reserves.From 1990 to 2015,58.9%of carbon storage of coastal wetland lost in coastal nature protected area(2.45 Tg),mainly due to the transformation of a large number of natural wetlands into artificial wetlands(salt pan and aquatic agriculture).The decreases of carbon storage mainly occurred in Yancheng Rare Birds,Shuangtai Estuary and Changli Gold Coast National Nature Reserve,carbon storage loss was 1.61 Tg,0.37 Tg and 0.18 Tg,respectively.This work provides a theoretical basis for rational development and protection of coastal wetlands,enhanced coastal carbon sinks and mitigating global climate change.Ultimately,some potential strategies are provided to mitigate the negative effects of land use change on carbon storage in coastal areas.