Simulation Research On City-scale Urban Growth Boundary Based On SSPs Scenario Prediction

As the country puts forward new requirements for land and space planning,in view of the problems of excessive urban space expansion and shortage of land resources in the process of urbanization,scientifically controlling urban growth boundaries is the key to solving the current disorderly urban expansion.This paper takes Kaifeng city as the research object,based on shared socioeconomic pathways(SSPs),predicts the future urban population,and then predicts the total urban land demand in the future.Using the constrained Logistic-CA method,comprehensively considering urban land use and ecological protection,and simulating the future development of the city with water as the constraint condition,the urban growth boundary is delineated from the perspective of multiple scenarios in the principle of ecological protection,and the reasonable expansion of urban space is realized.Identify reasonable spatial distribution patterns of urban growth boundaries and assess changes in ecological service value due to urban expansion.research shows:(1)By around 2050,the total population,age structure,working population and other demographic characteristics under the SSPs path will be quite different from those in 2010,and the population will show an obvious trend of aging.The estimated total future population of Kaifeng City under the SSPs path is quite different.By around 2050,the total population of the SSP5 path will be the largest,and the population of the SSP4 path will be the least.The difference between the two paths is 1,017,500.The SSP1,SSP3 and SSP4 pathways are relatively close in population.From the perspective of age structure,compared with2010,the proportion of the elderly population under the SSP1-5 pathway has increased.The population structure under the SSP1,SSP4 and SSP5 pathways presents an "inverted pyramid" and is in a period of population decline.SSP2 and SSP3 The path is in a stable population period.From the perspective of gender structure,the trend of female elderly population is higher than that of male elderly population in the elderly population over 65 years old.From the perspective of the main body of the population,the age group with the largest population under different paths is 40-64 years old,accounting for 47.6% of the total population,and the population shows an obvious trend of aging.From the perspective of labor force,under the next five SSP paths,the youth population and labor force population will decrease to varying degrees,and the proportion of the elderly population in the total population will increase greatly.The problem of population aging may be more serious under the SSP1,SSP4 and SSP5 pathways.(2)By about 2050,the urbanization level of Kaifeng City under the SSP scenario will show a convergence trend from fast growth to slow growth.Based on the setting that there will be no reverse urbanization rate in Kaifeng City in 2050,the future urbanization level is estimated,and the results show that because the development of urbanization is constrained by total population,economic conditions,agricultural production and other resource endowments,the urbanization level under different SSP scenarios shows a convergence trend from fast growth to slow growth.By 2050,the level of urbanization under the SSP1,SSP4 and SSP5 paths can reach 77.3%,with an average annual growth rate of 0.83%,;under the SSP2 and SSP3 paths,it can reach 74.4% and 67.6%,respectively,with an average annual growth rate of 0.73% and 0.53%,respectively.(3)Under the SSPs scenario,the urban expansion of Kaifeng City in the future has great commonalities.In addition to the connotative development,the urban expansion speed of Kaifeng City is relatively rapid.In the future,while the main urban area of Kaifeng City will expand to the surrounding areas,the western expansion will be the most rapid in the past.Significantly,the expansion trend of the remaining four counties along the traffic line is more obvious,and there is a point-axis development trend between the main urban area of Kaifeng,Lankao County and Qi County.Lankao County has an obvious trend of developing to the northeast.Weishi County and Qi County also expanded significantly in the south.The urban development of Tongxu County is relatively slow.The central area of Kaifeng,Lankao County and Xiangfu District are more closely linked,forming the growth center of Kaifeng City and promoting the overall development of Kaifeng City.The planning and development of future construction land will mainly focus on the west of the main urban area,and the centralized construction of Bianxi New District will become a new development space for Kaifeng City.Cities,counties and cities will absorb rural population through the development of manufacturing industries,and characteristic townships will develop private economy to attract farmers into small towns,and the permanent population of cities and towns will continue to increase.By continuously enhancing the attractiveness,carrying capacity and sustainable development capacity of cities and towns,scientifically organizing and planning urban functions,and forming regional emerging growth poles,the urbanization development of Kaifeng City will enter an important period of strategic opportunities.(4)The ecosystem service value of each land use type in Kaifeng City is mainly arable land and water area,and the encroachment of a large number of farmland by the city is the main reason for the reduction of ecological value.In 2015,the total value of ecosystem services in Kaifeng City was 9.347 billion yuan.From the perspective of land use types,the ecosystem service value of cultivated land was7.705 billion yuan,accounting for about 82.4% of the total value;the ecosystem service value of waters ranked second.1.476 billion yuan;the ecosystem service value of forest land is 142 million yuan;the ecosystem service value of grassland is only 24 million yuan,the smallest proportion.Under the two urban expansion scenarios focusing on urban development and ecological protection,the ecosystem service value of the SSP1-5 scenarios in 2030 and 2050 decreased,mainly due to the encroachment of a large amount of farmland by urban expansion.