Evaluation Of Wetland Damage And Simulation Of Wetland Future Changes In The Guangdong-Hong Kong-Macao Greater Bay Area

As one of the three major ecosystems on earth,formed by the interaction of land and water,wetlands have ecological,economic,and social benefits and play an important role in global environmental change.Wetland damage evaluation runs through the whole process of wetland survival and evolution,involving wetland pattern evolution,function performance,conservation,utilization,etc.It is significant in wetland research and has many application needs.The existing wetland damage evaluation faces the problems of not considering the factors of human activities disturbing wetlands thoroughly enough,and the results are not easy to compare;it is difficult to directly answer the questions of where wetlands should be protected and how to protect them,and the results are not effectively applied;the results do not accurately represent the spatial changes of wetland risks;the means of applying the analysis of the results are relatively limited,etc.Therefore,it is necessary to construct a new method for wetland damage evaluation to enhance the practicability of wetland damage evaluation.This study aims to construct a wetland damage index(WDI)to assess wetland damage in the Guangdong-Hong Kong-Macao Greater Bay Area(GBA)and to simulate future changes in wetlands under different scenarios.Firstly,the WDI is constructed to assess the damage status of wetlands by considering three aspects:wetland area change,ecological environment conditions,and human activity disturbance.Secondly,the relationship between WDI and wetland landscape pattern,wetland type,and wetland location is analyzed to study the wetland damage characteristics.The impact of wetland damage on the subsequent wetland evolution is studied,and an example analysis is combined to observe the indicative role of WDI on wetland evolution.Finally,future wetland changes for different scenarios are simulated and compared with current wetland damage to provide a reference for wetland conservation applications.This study draws the following conclusions:(1)The wetland area in the GBA declined from 2000 to 2020,and the distribution pattern was unchanged,with large differences in wetland area between different wetland types and different cities,and the decline of ponds was the main factor in the decline of wetland area.In the past 20 years,the wetland area in the GBA decreased from 6704.19 km~2 to 5872.03 km~2,a decrease of 12.40%,with large differences in wetland area between the west and east bank areas of the Pearl River and between cities.There are more wetlands in the west bank area,and rivers and ponds are widely distributed;the wetlands in the east bank area are less,mainly composed of rivers and reservoirs.Ponds and rivers are the main components of wetlands in the GBA.From 2000 to 2020,the area of ponds decreased by 17.1%,and the area of pond disappearance area accounted for 90.2%of the wetland disappearance area.(2)Wetland damage in the GBA from 2010 to 2020 has been mitigated,and the variation in wetland damage within the region is widening,with wetland damage characterized by wetland landscape fragmentation,variation by wetland type,and variation by wetland proximity to cities.From 2010 to 2020,the WDI of the GBA decreases from 0.291 to 0.285,but its standard deviation is increasing.The areas with more severe wetland damage are clustered and distributed in the urban built-up area in the middle of the GBA,and the areas with less damage are clustered in the ecological land around the GBA.The complex shape and fragmented distribution of wetland patches are the characteristics of wetland impairment in terms of landscape pattern.Wetland damage in rivers and ponds is higher in general.The closer to the city,the higher the degree of wetland damage,and it usually shows an increasing trend in the last decade.(3)Wetland damage is constrained by two factors:ecological conditions and human activity disturbance.While the ecological condition of the GBA improves in general from 2010to 2020,the disturbance faced by human activity rises.In the past 20 years,areas with the poorer ecological environment have expanded,but to a lesser extent than areas with a better ecological environment;the aggregation range of areas with stronger or weaker human activity disturbance is expanding,and the internal differences have increased.The intensification of anthropogenic disturbances,combined with the improvement of ecological conditions,have contributed to the reduction of wetland damage and the expansion of spatial differences in wetland damage as urbanization continues.(4)The drivers of the evolution of each type of wetland contribute differently,and the changes of each type of wetland in the GBA from 2020 to 2030 are limited by the expansion of construction land,with the greatest demand for wetland area in ecological protection or sustainable development scenarios.Rivers and reservoirs are driven more by natural factors;lakes and ponds are driven more by socio-economic factors.The area of each type of wetland varies for different future scenarios,and changes in wetland area are limited by the extent of expansion of built-up land for different scenarios.Among the four scenarios,the variation of rivers,reservoirs,and lakes is not significant,and the demand for wetland area is low in the baseline or economic development scenarios and high in the ecological protection or sustainable development scenarios.The change in future wetland demand is mainly reflected in ponds.The area of ponds in the sustainable development scenario is between the economic development and ecological protection scenarios,reflecting the balance of economic and ecological benefits.(5)The WDI is indicative of the subsequent wetland evolution and is applicable to different scenarios of future land change,and its application can be further extended according to practical needs.In general,as the WDI of the wetland grid becomes larger,the greater the probability that the wetland share will show a decrease;the lower the WDI,the greater the probability that the wetland share will fluctuate or increase within a smaller range.WDI is indicative of future wetland evolution except for the ecological protection scenario,but it is not an absolute predictor of wetland evolution,which is also influenced by planning,environmental protection,and other factors.The calculation of WDI is based on the land area,and the analysis of WDI from nearshore to offshore can be achieved by considering the decreasing diffusion of coastal WDI outward.