Effects Of Anthropogenic Activity On Mangrove Species Distribution In China

Mangroves are shrubs or small trees grow in the marine-terrestrial ecotone,they provide important ecosystem services.The mangroves in China are acknowledged as the northern boundary of global mangrove extent and are under relatively more fragile and sensitive ecosystem.Several mangrove species in China are prone to regional extinction under the impact of climate change and human disturbance.Differentiated from other ecotypes,the mangrove ecosystem is functionally characterized by its extremely low plant diversity in supporting its high animal diversity,thereby,the extinction of a single plant species may lead to a serious degradation of the whole community.This study documented the mangrove species distribution and numbers in China through surveys covering 107 administrative regions in the south of Wenling,Taizhou,Zhejiang Province.Those regions including Zhejiang(4 cities and 7 regions),Fujian(7 cities and 16 regions),Guangdong(13 cities and 39 regions),Guangxi(3 cities and 10 regions),Hainan(7 cities and 5 counties and 19 regions),Hong Kong(1 region),Macao(1 region)and Taiwan(14 regions,including Lantau Island,Ryukyu Island and Penghu Islands).The surveys were conducted through historical data collecting and supplementary field visiting,the historical data were collected from the experts’investigation started at 1999,and the supplementary surveys were carried out begin at 2018 among 27 regions over 90 days.This paper clarified several traits of mangrove communities,including the main characteristics,distribution extent,filed survival status and potential risking factors.The mangrove extent was visualized through cartography tools,and each mangrove species was mapped to show spatial extent variance among species.Based on the changes of species abundance distribution of mangrove plants in each survey area,mangrove plants were grouped into native true mangrove/mangrove associate plants,non-native true mangrove/mangrove associate plants,and extinct true mangrove/mangrove associate plants,and the species abundance of mangrove communities were mapped over these groups.Derived from the temporal changes of the mangrove communities composition,human activity to the mangrove communities in the Modern Chinese history were firstly confirmed,and were roughly divided into "no human activity","negative human activity" and "positive+negative human activity",corresponding to the community species abundance groups of "native mangrove+extinct mangrove","native mangrove" and "native mangrove+non-native mangrove",respectively.And,within these paired groups,analysis has been made on impacts of different types of human activity on the species abundance along the latitudinal gradient.Finally,the continuous changing trend of biodiversity and the hot spot of the mangrove communities were mapped at high precision under the scenarios of different types of human activity along China southeastern coastline,using the inverse distance weight interpolation method.The main conclusion are as follows:1.There are four species of mangrove plants in Zhejiang;and 19 species in Fujian,among which four are rare and endangered plants(REPs)(accounting for 21.05%);27 species in Guangdong,with seven REPs(25.93%);21 species in Guangxi,with three REPs(14.29%);39 species in Hainan,with eighteen REPs(46.15%);18 species in Hong Kong,with one REPs(46.15%);18 species in Taiwan,with four REPs(22.22%);and there are 13 species in Macao.2.Based on the significant historical evidences,the types of human activity were break down into three groups,mainly "positive human activity" and "negative human activity",and were related to the mangrove distribution data.It emerged that the negative correlation between species richness and latitude remains unchanged under the impact of negative or positive human activity.The negative human activity has led to the regional extinction of certain mangrove species,which has narrowed the latitudinal range of these species’ distribution.Whilst,the natural north distribution boundary was seen moving south,and concurrently going with the decline of the biodiversity of mangrove communities.The positive human activity has widened the latitudinal range of the distribution of certain mangrove species and has broken the biogeographical limitation of the natural distribution of these species.Furthermore,it has also extended the boundary of mangrove biological diffusion,and even offsets the negative impact of negative human activity on the species richness of the community.For example,the northern boundary of the natural distribution of Rhizophora stylosa was earlily recorded as Shanwei,Guangdong Province,while up to now,the wild natural R.stylosa in the north of Yangxi,Guangdong Province has basically been reported as extinct.And after the artificial introduction,the northernmost region of the distribution of R.stylosa has northward to Xiamen,Fujian Province.3.In this paper,the biodiversity hotspots of mangrove communities in China have been positioned:Quanzhou Bay,Jiulong Estuary and Zhang Estuary in Fujian Province;Daya Bay in Guangdong Province,Futian,Baguang in Shenzhen City,Qi’ao Island in Zhuhai City,Hailing Island in Yangjiang City,Shaba Bay and Leizhou Peninsula;Mai Po Nature Reserve in Hong Kong City;Pearl Bay in Guangxi Province;Dongzhai Port,Xinying Bay and Qinglan Port,Shimei Bay,Tielu Port,Qingmei Port in Hainan Province.