Ecological risk assessment and ecological security pattern optimization in the middle reaches of the Yellow River based on ERI+MCR model

The middle reaches of the Yellow River represent an important area for the protection and development of the Yellow River Basin.Most of the area of the river basin is within the Loess Plateau,which establishes it as a fragile ecological environment.Firstly,using high-resolution data of land use in the watershed from the past 30 years,landscape ecological risk(LER)sample units are defined and an ecological risk index(ERI)model is constructed.Kriging interpolation is used to display the LER spatial patterns,and the temporal and spatial evolution of risk is examined.Secondly,the spatial evolution of land use landscape change(LULC)is analyzed,and the correlation between land use landscape and ecological risk is discussed.Finally,Based on the LER model,a risk-based minimum cumulative resistance(MCR)model is established,and a comprehensive protection and management network system for the ecological source-corridor-node system designed.The results suggest that in the past 30 years,LER has a high spatial correlation and areas with extremely high ecological risks are concentrated in northwest and southeast areas of the region,of which the northwest area accounts for the highest proportion.Risk intensity is closely related to the spatial pattern of land use landscape.ERI values of forestland,grasslands,and unused land and farmland are low,medium,and high,respectively.The trend of risk evolution is“overall improvement and partial deterioration”.Man-made construction and exploitation is the most direct reason for the increase of local ecological risks.The high ecological-risk areas in the northwest are dominated by deserts which reduce excessive interference by human activities on the natural landscape.Recommendations are:high-quality farmland should be protected;forestland should be restored and rebuilt;repair and adjust the existing ecosystem to assist in landscape regeneration and reconstruction;utilize the overall planning vision of“mountain,water,forest,field,lake,grass,sand”to design a management project at the basin scale;adhere to problem-oriented and precise policy implementation.

Regional ecosystem services relationships and their potential driving factors in the Yellow River Basin,China

The Yellow River Basin(YRB)occupies an important position in China’s socioeconomic development and ecological conservation efforts.Understanding the spatiotemporal characteristics of the relationships among multiple ecosystem services(ESs)and their drivers is crucial for regional sustainable development and human-earth system coordination.This study simulated food production(FP),water yield(WY),net primary production(NPP),soil conservation(SC),and habitat quality(HQ)in the YRB from 2000 to 2020,and evaluated the spatial evolution and the relationship of ESs at the raster scale.Redundancy analysis was used to identify the impact of natural,socioeconomic,and landscape patterns on the relationship between ESs.The results demonstrated that the average HQ per unit area decreased by 18.10%,while SC,NPP,WY,and FP increased by 42.68%,47.63%,30.82%,and 67.10%,respectively,from 2000 to 2020.The relationship between ESs in the YRB was dominated by weak trade-offs and weak synergies at a temporal scale,with the trade-offs strengthened in the Upper Yellow River Basin(UYRB)and the Middle Yellow River Basin(MYRB),and synergies strengthened in the Lower Yellow River Basin(LYRB).At the spatial scale,the relationships between HQ and WY,HQ and SC,HQ and NPP,FP and SC,and FP and HQ were all dominated by trade-offs,while other ES pairs were mostly based on synergistic relationships.In the YRB,the relationships among ESs were mainly influenced by human disturbance,precipitation,and land-use and exploitation intensity.Specifically,the trade-offs among ESs in the UYRB were primarily affected by precipitation,and those in the MYRB and LYRB by human disturbance.The heterogeneity of the landscape could also effectively promote synergies among ESs.This study could provide insights into trade-offs and synergies among ESs and their driving forces and lay a foundation for ecological restoration and sustainable development of ESs in the YRB.

Spatiotemporal Trends and Ecological Determinants in Population by Elevation in China Since 1990

It is very important to understand the ecological and socio-economic factors in population distribution and their changes over time for the compilation of regional development planning and the guidance of rational population flow.Using surface-based population data for China from 1990 to 2015,the national distribution and dynamics of the human population by elevation are quantified based on 1-km cell-size gridded distribution datasets and 1-km cell-size DEM(digital elevation model).A geographical detector model is used to quantitatively analyze the dominant role of natural geographical factors,such as topography and climate,on the spatial distribution of population.Results show that:1)the population size and density decrease rapidly with elevation below 1000 m above the sea level,and the gap in population density between low-altitude areas and high-altitude areas increases with time because of the continuous growth of population density in low-altitude areas;2)the distribution of the population can be divided into five steps according to integrated population density(IPD),in proportions of 43∶35∶21∶1∶0,and that these proportions have remained stable over the last 25 yr;3)the basic pattern of population spatial distribution is determined by natural geographical environment factors,such as topography,climate,geomorphology,and their interactions;and 4)the development of society and the economy are the driving forces for the dynamic change in the population distribution during the study period,with the distribution pattern and dynamics of population by altitude in China providing a comprehensive reflection of various geographical elements on different spatial scales.