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Quantitatively predicting the impacts of climate change on water demands of various crops is essential for developing measures to ensure food security, sustainable agriculture, and water resources management, especially in arid regions. This study explored the water footprints (WFs) of nine major crops in the middle and downstream areas of Shule River Basin, Northwest China, from 1989 to 2020 using the WF theory and CROPWAT model and predicted the future WFs of these crops under four emission and socio-economic pathway (SSPs-RCPs) scenarios, which provides scientific support for actively responding to the negative impacts of climate change in arid regions. Results indicated: (1) an increasing trend of the overall crop WF, with blue WF accounting for 80.31-99.33% of the total WF in the last 30 years. Owing to differences of planting structure, water-conservation technologies, and other factors, the multi-year average WF per unit area of crops was 0.75 × 104 m3 hm-2 in downstream area, which was higher than that in midstream area (0.57 × 104 m3 hm-2) in the last 30 years; therefore agricultural water use efficiency in the downstream area was lower than that in the midstream area, implying that the midstream area has more efficient agricultural water utilization. (2) an initial increase and then decrease of crop WFs in the study area under SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios by the end of the century, reaching their peak in 2030s which was higher than that from 1989 to 2020; with the maximum growth rates in the midstream area ranging from -0.85% in SSP5-8.5 to 5.33% in SSP2-4.5 and 29.74% in SSP5-8.5 to 34.71% in SSP2-4.5 in the downstream area. The local agricultural water demand would continue to increase and water scarcity issues would be more severe in the next 10-20 years, affecting downstream areas more. Under the SSP3-7.0 scenario, crop WF values of the midstream and downstream regions will be 2.63 × 108 m3 and 4.22 × 108 m3 in 2030, respectively, which is significantly higher than those of other scenarios and show a long-term growth trend. The growth rate of the midstream and downstream regions will reach 44.71% and 81.12%, respectively, by the end of this century, so the local agricultural water use would be facing more strain if this scenario materializes in the future. Therefore, the Shule River Basin should encourage development of water-saving irrigation technologies, adjust the planting ratio of high water consuming crops, and identify other measures to improve water resource utilization efficiency to cope with future water resource pressures.

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Agricultural irrigation and resettlement have significant impacts on carbon storage in arid inland river basins. With the background of "Comprehensive development measures for agricultural irrigation and resettlement in Shule River Basin (SRB)", this paper uses land use data to estimate regional carbon storage through InVEST model and revises the result by using net ecosystem productivity (NEP). The influence of land use change on carbon storage and the driving factors of carbon storage spatial differentiation were analyzed by using the optimal parameters geographical detector (OPGD). It can be inferred from the results that: (1) During 2000-2020, the increase of cropland and grassland area is the main type of land use change in the central oasis area of Yumen City and Guazhou County. Cumulative carbon storage increased by 1.75 × 107 t. (2) NEP in the central oasis area of Yumen City and Guazhou County showed a fluctuating upward trend, and it generally behaves as a carbon sink. The average annual NEP was 1.78 × 105 t, and the carbon sink increased by 0.95 × 105 t. (3) The main factors responsible for driving are vegetation, elevation, potential evapotranspiration, and precipitation. The explanatory power of each factor in carbon storage spatial differentiation was enhanced by the interaction between natural and anthropogenic factors. The interaction between vegetation and the human factor is more significant than that of the human single factor. (4) Agricultural irrigation and resettlement measures did not cause a decline in ecosystem carbon storage in Yumen City and Guazhou County in the central part of SRB. Conversely, the region's ecosystems have seen an increase in carbon storage as a result of the increase in cropland. (5) The introduction of the NEP modification method and the OPGD model improves the accuracy of carbon storage estimation and obtains better driving results in spatial differentiation. The study idea provides a new perspective for the estimation of carbon storage as a whole, and provides a reference basis for the formulation of ecological protection policies.

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Construction and optimization of ecological security network is an efficient way to ensure regional ecological security and achieve sustainable development. Based on the morphological spatial pattern analysis method, circuit theory and other methods, we constructed the ecological security network of the Shule River Basin. The PLUS model was used to predict the land use change in 2030, with the aim to explore the current ecological protection direction and propose reasonable optimization strategies. The results showed that there were 20 ecological sources in the Shule River Basin, with a total area of 15774.08 km2, accounting for 12.3% of the total area of study area. The ecological sources were mainly distributed in the south part of the study area. A total of 37 potential ecological corridors were extracted, including 22 important ecological corridors, which showed the overall spatial characteristics of vertical distribution. Meanwhile, 19 ecological pinch points and 17 ecological obstacle points were identified. We predicted that the expansion of construction land would continue to squeeze the ecological space by 2030, and identified 6 warning areas of ecological protection space to effectively avoid conflicts between ecological protection and economic development. After optimization, 14 new ecological sources and 17 stepping stones were added, and the circuitry, ratio of line to node and connectivity index of the ecological security network increased by 18.3%, 15.5%, and 8.2% respectively compared with those before optimization, forming a structurally stable ecological security network. The results could provide scientific basis for ecological security network optimization and ecological restoration.

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RESUMEN

Landscape pattern evolution leads to changes of landscape spatial structure, which are intuitively reflected in the changes of ecosystem structure and composition and finally affect ecological security. In this paper, we assessed the spatiotemporal variation of the ecological security and landscape pattern of the middle and lower reaches of Shule River Basin in 1987-2015. Further, we analyzed the correlation between the ecological security and landscape pattern of the study region and correlation coefficients were calculated. On this basis, the key landscape pattern indices influencing the ecological security of the study region were identified. This may provide useful information for ecological regulation and design. The results show that: (1) From 1987 to 2015, the ecological security in the middle and lower reaches of the Shule River Basin was of medium or low level, showing periodic "U" shaped fluctuations, and the fluctuation period was gradually shortened. In addition, there was an overall spatial pattern of "high ecological security in the west, middle and south and low ecological security in the east". (2) The landscape pattern showed clear stage characteristics. The complexity of landscape pattern increased from 1987 to 1996 and decreased after 1996. (3) Landscape size, shape, quantity, type and spatial configuration had important impacts on ecological security and showed significant temporal variation. In a period when the influence of human activities was weak, ecological security was mainly related to landscape area indices. With increase in human activities, landscape shape, fragmentation and connectivity changed greatly, which led to changes in the structure and composition of ecosystem, thus finally affecting ecological security.

RESUMEN

Shule River Basin is a typical arid inland river basin and ecoenvironment-fragile region. Comprehensive evaluation of ecosystem quality in the Shule River basin is of great significance. The ecosystem productivity index (EPI), the ecosystem stability index (ESI) and the ecosystem bea-ring capacity index (EBCI) were proposed to build a remote sensing comprehensive evaluation mo-del to evaluate the ecosystem quality of Shule River basin during 2001-2010. The results showed that the mean ecosystem quality value in the Shule River basin was 43.21, which was at a relatively low level. The values of EPI, ESI, EBCI were 47.16, 58.09 and 28.52, respectively, indicating that ecosystem carrying capacity in the Shule River basin was poor in the period from 2001 to 2010. However, EPI and EBCI rose by 18.9％ and 20.1％, respectively, but ESI decreased slightly by 9.4%. The ecosystem quality showed a trend of increasing first and then decreasing from 2001 to 2010. The average ecosystem quality values in 2001, 2005 and 2010 were 43.71, 44.80 and 41.13, respectively. The farmland ecosystem quality was better than that of the other ecosystem types, and the water area ecosystem quality was the lowest. Overall, the comprehensive evaluation value of the artificial ecosystem quality was 46.43, which was significantly higher than that of the natural ecosystems.

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