Ecosystem Health Assessment Of Urban Agglomeration Based On Hidden Markov Model

As a highly mature spatial organization form in the process of urbanization development,urban agglomerations are areas with more prominent ecological and environmental problems.To evaluate the state of ecosystems in urban agglomerations,a comprehensive and scientific concept called ecosystem health is commonly introduced.The evaluation and analysis of ecosystem health in urban agglomeration,especially from a multi-temporal perspective,is crucial for local ecological construction and sustainable development.In this study,a typical highly urbanized area in China-Shanghai and Hangzhou Bay(SHB)urban agglomeration was selected as the study area.With the advance of quickness and efficiency of remote sensing technology in acquiring spatial data and the theoretical basis of landscape ecology,the ecosystem health of the SHB urban agglomeration was assessed and analyzed at multiple administrative scale(city and county)using vigor-organization-resilience(VOR)framework.Moreover,the hidden markov model(HMM)was also introduced to assist in determining explicit and implicit states in ecosystem health assessment.The evaluation system constructed in this study included model selection,indicator calculation and precision validation,exploring the feasibility of HMM in the field of ecosystem health assessment and simulation.Finally,the urbanization process and evolution of ecosystem health of urban agglomeration were discussed.Overall,the major work of this study were as follows:1)The landscape pattern evolution of SHB urban agglomeration was analyzed at the multi-cities,city and county scales.The results show that forest and farmland,which belong to the landscape matrix,were the main land use types in the study area,and water,grassland and construction land were mosaic among them in the form of patches or corridors.As for the urban agglomeration as a whole,the landscape diversity tended to increase with time,while the contagion index and cohesion index decreased.But at city and county scales,the changes of landscape index among cities showed strong spatial heterogeneity.2)The ecosystem health evolution of study area was analyzed using VOR framework.Under different scales,the eastern part of Huzhou,the northeastern part of Hangzhou,the northern part of Shaoxing and the northern coastal area of Ningbo were appeared to be the transition zones.Bordered by them,the health level in the southwest was better than that in the northeast.Furthermore,regardless of the analytical scale,the proportion of grids at well level tended to decrease with time,which reflected that the health level of regional ecosystem showed a downward trend.3)A specific scheme of introducing HMM into ecosystem health simulation of urban agglomeration was designed,and the results of traditional VOR framework were used as reference group to verify the feasibility of the scheme and to determine a suitable scale for research.In addition,two kinds of parameter learning schemes were proposed.The results showed that,firstly,for this study area,8 km grid scale is optimal.Secondly,during the study period,the decoding results of HMM based on mathematical statistics were similar to the calculation results of traditional VOR model.The simulation accuracy of each time node was above 0.8,which indicated that it was feasible to introduce HMM into ecosystem health simulation of urban agglomeration.At last,the HMM parameters obtained by extensible sequence method were used to decode under the constraints of explicit state of ecosystem.4)The FLUS model was introduced to simulate the land use in the study area,and an ecosystem health prediction scheme was constructed based on VOR-Naive Bayes algorithm and decoding results under constraints.The simulation results showed that,for both schemes,the ecosystem health level in the study area was not well in 2019.The ecosystem health of Shanghai was still at the lowest level,and the ecosystem health levels of Ningbo and Huzhou were characterized by staggered distribution.In order to better improve the health level of regional ecosystem,the cities of urban agglomeration should strengthen the linkage mechanism of ecological environment protection,delimit the "three zones and three lines",adhere to the principle of "joint efforts to protect and not to develop",strengthen environmental supervision of the areas along Hangzhou Bay and Huangpu River,and promote the regional ecological construction and green sustainable development.