| With rapid urbanization and industrialization,the conflict among living land,producing land and ecological land is intensifying.How to coordinate the contradiction between urban construction space and ecological space has become one of the major topics in the field of land and space planning in China.Establishing a regional ecological security pattern is an important way to alleviate the contradiction between urbanization development and ecological protection.It is also important for rationally allocating resources and ensuring sustainable development of national land space.Ecological sources and ecological corridors are two important components of the ecological security pattern,and how to identify them is critical.Landscape ecological risk assessment is a significant step for land and space planning and critical for regional ecological security pattern optimization.However,current studies ignored future land use and ecological risk change scenarios during landscape ecological risk assessment,and thus lacked the proactive or predictive prevention from future ecological risks when optimizing the ecological securing pattern.In this thesis,taking Guangdong-Hong Kong-Macao Greater Bay Area as an example,we identified the ecological security pattern based on the paradigm of"ecological source-ecological resistance surface-ecological corridor"and evaluated the regional landscape ecological risk by integrated future land use under different climate scenarios and regional security pattern of 2018.Afterwards,we revised the ecological resistance surface based on the results of landscape ecological risk and extracted potential corridors for preventing future ecological risks to realize the ecological security pattern optimization.Main findings are as follows.(1)The total area of extremely important regions in the study area was 32552.6 km~2,and mainly located in the coastal areas of Hong Kong,Shenzhen,eastern Huizhou,northeastern Guangzhou,northwestern Zhaoqing,western Foshan and southwestern Jiangmen,with the characteristics of high around while low in the middle of the region.The total area of extremely sensitive regions in the study area was 33826.6 km~2,mainly distributed in the peripheral mountain forest areas,as well as the Xijiang River,Beijiang River and Pearl River in the central region.(2)The total area of ecological source in the study area was 20370.8 km~2,accounting for36.7%of the total area and mainly located in mountainous and hilly areas with extensive woodlands in the north part as well as nature reserves and country parks in Hong Kong and Macao.Cities in the central part of study area such as Dongguan,Foshan and Guangzhou,had no ecological sources due to rapid land urbanization,high pollution levels and low ecological services supply.(3)There were 36 ecological corridors in the study area with a total length of 2300.4 km and were peripherally distributed around the east and west part of the region.Corridor priority grading results showed that the number of high importance and weak connectivity corridors were the highest(22),low importance and weak connectively and low importance and strong connectively corridors followed by(6/5),and high importance and strong connectivity corridors were the lowest(3).For different types of corridors,targeted protection and management measures should be adopted according to their local conditions.(4)In 2050 and 2100,the landscape ecological risk of the study area was overall at low or medium risk level.The areas of the low and medium risk regions accounted for 41.9%–77.7%and 11.3%–41.9%of the study area,respectively.The landscape ecological risk was high in the middle while low in the surrounding areas of the region,and the high risk regions gradually spread to the periphery with time.(5)The low and medium greenhouse gas emission scenarios(RCP2.6 and RCP4.5)limited the expansion of construction land.Under RCP2.6 and RCP4.5 scenarios,future land use change was mainly manifested in the increase of cultivated land by occupying the forest land and construction land.Under the high greenhouse gas emission scenarios(RCP6.0 and RCP8.5),construction land expanded significantly by mainly occupying cultivated land although with a few forests converted into cultivated land.In the late stage of RCP8.5 scenario,a few forests were degraded into grassland due to the greenhouse effect.(6)Under different climate scenarios,urban expansion encroaches on multiple ecosystem services at the same time.In 2050 and 2100,urban expansion encroached on 650.8 km~2–2305.3km~2extremely important regions with two or more extremely important ecosystem services,accounting for 85.3%–86.3%of the study area,respectively.Urban expansion mainly encroached on a single type of extremely sensitive regions.In 2050 and 2100,urban expansion encroached on 350.5–1836.0 km~2(35.2%–49.0%),308.9–690.4 km~2(18.5%–31.0%)and109.8–421.4 km~2(11.0%–12.7%)of extremely sensitive regions of habitat,water,and atmosphere,respectively.(7)Under low and medium greenhouse gas emission scenarios(RCP2.6 and RCP4.5),the ecological source of the study area was mainly occupied by cultivated land especially in Zhaoqing,Huizhou,Jiangmen and Guangzhou.Under high greenhouse gas emission scenarios(RCP6.0 and RCP8.5),the ecological source was mainly occupied by construction land especially in Zhaoqing,Hong Kong,Shenzhen and Huizhou.he ecological breakpoints in the corridors were more under high greenhouse gas emission scenario.Furthermore,with the expansion of construction land,the ecological corridor breakpoint increased under different climate scenarios from 2050 to 2100.(8)Considering the increase of ecological breakpoints and landscape ecological risks in the study area and in order to maintain a good ecological security pattern,the number of corridors should be increased by 37–47 during 2050-2100,with the increase of 37–45,38–41,39–44 and 43–47 under RCP2.6,RCP4.5,RCP6.0 and RCP8.0 climate scenarios,respectively. |
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