Research Article |
Corresponding author: Haiguang Hao ( haohg@craes.org.cn ) Academic editor: Francisco Javier Bonet García
© 2023 Ding Wang, Haiguang Hao, Hao Liu, Lihui Sun, Yuyang Li.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Wang D, Hao H, Liu H, Sun L, Li Y (2023) Dynamic change of habitat quality and its key driving factors in Ningxia Hui Autonomous Region, China. Nature Conservation 53: 125-155. https://doi.org/10.3897/natureconservation.53.102810
|
Habitat quality reflects the level of biodiversity, and habitat maintenance functions are related to human well-being and ecosystem stability. Ningxia Hui Autonomous Region is a typical ecologically fragile region in Western China with complex human-nature relationships. Maintaining good habitat is not only a fundamental requirement for biodiversity conservation but also a necessary path for sustainable regional development. In this study, we assessed and analysed the spatial and temporal patterns and changes in habitat quality in Ningxia from 2000 to 2020, and explored the driving factors of habitat quality using a geographically weighted regression (GWR) model. The results indicated: (1) The overall habitat quality level in Ningxia was low to intermediate, with an upwards and then downwards trend during the past 20 years, showing a small change in overall magnitude. (2) The high- and higher-level habitat quality patches in Ningxia were mainly distributed in areas with high vegetation cover, such as the Helan Mountain and Liupan Mountain. The patches of moderate-level habitat quality mainly included cultivated land, while the low- and lower-level patches were mainly distributed in areas subjected to more frequent human activities, such as cultivated land and construction land. (3) The spatial and temporal distribution patterns and changes in habitat quality in Ningxia from 2000 to 2020 were mainly influenced by fractional vegetation cover (FVC), soil moisture content (SMC), proportion of construction land area (PCL), and proportion of cultivated land area (CLP). Among them, FVC and SMC were positive driving factors, and PCL and CLP were negative driving factors. The results support that increasing vegetation cover and reducing anthropogenic disturbance to natural habitats are important measures to maintain fragile habitats and that key ecological function areas such as nature reserves are crucial for habitat quality protection in ecologically fragile areas.
Driving factors, geographically weighted regression (GWR), habitat quality, Ningxia Hui Autonomous Region, spatiotemporal pattern
Habitat quality refers to the ability of an ecological environment to provide suitable conditions for the sustainable survival and development of individuals, populations or communities, reflecting the richness of biodiversity in a region, and it is related to human well-being (
A favourable habitat condition means that various ecological factors in the ecosystem meet the needs of population survival and reproduction, and the orderly differentiation of biological ecological niches will achieve a balanced and stable ecosystem function. Additionally, habitat maintenance is an ecosystem service that is of great concern to humans (
Habitat quality assessments include both ecological and geographic perspectives. Early studies focused on the substantial impacts of human activities on plant and animal habitats, and the research methods and contents were more biased towards natural and ecological properties (
As land use/land cover (LULC) change has become the focus of global change research (
Currently, humans are facing a serious biodiversity crisis, and habitat destruction is one of the most serious challenges threatening biodiversity conservation (
The current methods used to investigate the factors affecting habitat quality mainly include spatial exploratory analysis, spatial econometric analysis, multiple regression analysis, grey correlation analysis, and Moran’s I spatial autocorrelation index (
In summary, this study selected the Ningxia Hui Autonomous Region (hereinafter referred to as Ningxia), a typical ecologically fragile region in Western China, as the study area, collected raw data on land use, NDVI, and temperature from 2000 to 2020, and analysed the spatial and temporal patterns of habitat quality and their changes in the past 20 years based on remote sensing and GIS analysis. Based on the objective fact that the distribution of habitat quality in Ningxia is spatially heterogeneous, the GWR model with optimal fitting parameters was finally used to investigate the key factors driving the distribution and changes in habitat quality in Ningxia.
Ningxia (35°14'–39°23'N, 104°17'–107°39'E) (Fig.
In this study, the habitat quality module of the InVEST model was used to assess habitat quality in Ningxia, and the habitat quality index was calculated as follows:
(2.1.1)
where Qxj is the habitat quality of raster x in land use type j; k is the half-saturation parameter, whose value is half of the resolution of the raster data in the study area and is generally 1/2 of the maximum value of habitat degradation; Hj is the habitat suitability of land use type j, whose value is usually 0~1; z is the normalization constant, which is usually set to 2.5; and Dxj is the level of stress to which raster x of land use type j is subjected, i.e., the degree of habitat degradation. The degree of habitat degradation is the intensity of habitat disturbance by threat sources and is calculated as follows:
(2.1.2)
(Linear decay) (2.1.3)
(Exponential decay) (2.1.4)
where Dxj is the degree of habitat degradation; R is the number of stressors; y is the number of grids in the raster layer of stressor r; yr is the number of grids occupied by stressors; wr is the stressor weight; ry is the stressor value of raster y; βx is the accessibility level of raster x, which is not considered in this study; sjr is the sensitivity of habitat type j to stressor r; irxy is the stress factor value ry of raster y on the stress level of habitat raster x; dxy is the linear distance between raster x and raster y; and drmax is the maximum stress distance of threat source r. The higher the calculated score is, the greater the threat level caused by the threat factor to the habitat and the higher the degree of habitat degradation.
Based on the InVEST model manual and with reference to previous research results on habitat quality in Ningxia and the arid and semiarid regions of Northwest China (
Ecological threat factors and their maximum impact distances and weights.
Threat Factor | Impact Distance/km | Weight | Spatial Decline Type |
---|---|---|---|
Paddy Field | 4 | 0.15 | Linear Decline |
Dryland | 3 | 0.2 | Linear Decline |
Urban Land | 5 | 0.3 | Exponential Decline |
Rural Settlements | 4 | 0.3 | Exponential Decline |
Other Construction Land | 8 | 0.2 | Linear Decline |
Type | Habitat suitability | Paddy field | Dryland | Rural settlement | Urban land | Other construction land |
---|---|---|---|---|---|---|
Paddy Field | 0.6 | 0.3 | 0.2 | 0.35 | 0.5 | 0.45 |
Dryland | 0.4 | 0.3 | 0.2 | 0.35 | 0.5 | 0.4 |
Forested Land | 1 | 0.8 | 0.7 | 0.85 | 1 | 0.6 |
Shrubland | 1 | 0.4 | 0.3 | 0.45 | 0.6 | 0.4 |
Sparse Woodland | 1 | 0.85 | 0.75 | 0.9 | 1 | 0.65 |
Other Forest Land | 1 | 0.9 | 0.8 | 0.95 | 1 | 0.7 |
High Coverage Grassland | 0.85 | 0.4 | 0.3 | 0.45 | 0.6 | 0.6 |
Medium Coverage Grassland | 0.8 | 0.45 | 0.35 | 0.5 | 0.65 | 0.7 |
Low Coverage Grassland | 0.75 | 0.5 | 0.4 | 0.55 | 0.7 | 0.8 |
Canal | 1 | 0.7 | 0.6 | 0.75 | 0.9 | 0.5 |
Lake | 1 | 0.7 | 0.6 | 0.75 | 0.9 | 0.5 |
Reservoir Pit | 1 | 0.7 | 0.6 | 0.75 | 0.9 | 0.5 |
Beach Land | 0.6 | 0.75 | 0.65 | 0.75 | 0.95 | 0.55 |
Urban Land | 0 | 0 | 0 | 0.8 | 0 | 0 |
Rural Settlements | 0 | 0 | 0 | 0 | 0 | 0 |
Other Construction Land | 0 | 0 | 0 | 0 | 0 | 0 |
Unused Land | 0 | 0 | 0 | 0 | 0 | 0 |
The rate of change in habitat quality was calculated using the terminal habitat quality minus the initial habitat quality with the following equation:
(2.2)
where KT is the rate of change in habitat quality over time T. This study had a 5-year cycle; HQo is the size of habitat quality at the beginning of the study, HQi is the size of habitat quality at the end of the study, and the raster resolution is 30 m.
In this study, the global Moran’s I index was used to describe whether habitat quality in the study area had a clustering effect on a global scale, and the local Moran’s I index was used to reflect the spatial autocorrelation of habitat quality in the subregion. The spatial autocorrelation analysis was performed in ArcGIS 10.7 software.
(2.3.1)
(2.3.2)
where xi and xj are the values of variable x taken on neighbouring cells, x is the attribute value of the n location variables, x̄ is the mean of the attribute values of the spatial variables, ωij is the spatial weight matrix of raster i and raster j, and n is the total number of rasters.
Pearson correlation regression, the least squares model (OLS), and geographically weighted regression models were used to explore the characteristics of driving factors acting on habitat quality in Ningxia. The GWR model is a local regression model that embeds the geographic location of the data into the regression parameters, allowing for local parameter estimation. In this study, the geographically weighted regression weight function was chosen as a Gaussian function (Adaptive Gaussian), and its calibration was performed using an adaptive approach (Adaptive).
(2.4)
where yi is the dependent variable at sample point i, xik is the observed value of the kth variable at the ith point, (µi, vi)is the location coordinate of the ith point, βo(µi, vi) is the intercept, βk(µi, vi) is the regression coefficient of the ith, and εi is the error term.
Based on the results of previous studies on the driving factors of habitat quality in the Loess Plateau and Western China and the actual characteristics of the ecological environment in Ningxia (
Indicators | Abbreviation | Unit |
---|---|---|
Net Primary Productivity | NPP | gC/(m²*a) |
Fractional Vegetation Cover | FVC | % |
Mean Annual Precipitation | MAP | mm |
Drainage Density | DRA | km/km2 |
Elevation | ELE | m |
Slope | SLP | ° |
Degree of Relief | DRF | m |
Soil Moisture Content | SMC | m3/m3 |
Average Annual Temperature | AAT | °C |
Proportion of Cultivated Land | PCL | % |
The Proportion of Construction Land | CLP | % |
Population Density | POP | person/km2 |
Road Network Density | RND | km/km2 |
Nighttime Light Index | NLI | DN |
Regional GDP | GDP | 104 Yuan (¥) /km2 |
Closest Distance to Road Network | DRN | m |
The data in this study included habitat quality assessment data and driving regression data, and the InVEST model habitat quality assessment mainly used five periods of land use dataset from 2000 to 2020. The dataset were obtained from the Resource and Environmental Science and Data Center of the Chinese Academy of Sciences (https://www.resdc.cn/) at a resolution of 30 m. NDVI data were obtained from the 30 m annual maximum NDVI dataset of China at the National Ecological Science Data Center of China (http://www.nesdc.org.cn/). Net primary productivity data were obtained from the MOD17A3HGF Version 6.0 product (https://www.earthdata.nasa.gov/). Geospatial information data included the 2021 version of 1:1 million public geographic basic information dataset (https://www.webmap.cn/commres.do?method=result100W) and ALOS 12.5 m DEM data (https://www.gscloud.cn/). GDP and Population data were obtained from the 1 km-grid GDP dataset of China (https://www.resdc.cn/) and the 1 km-grid population dataset of China (https://www.resdc.cn/). Soil water content data were obtained from the Soil Moisture in China dataset (2002–2018) (http://data.tpdc.ac.cn/zh-hans/). A 1-km monthly mean temperature dataset for China (1901–2021), a 1-km monthly precipitation dataset for China (1901–2022), and the Prolonged Artificial Nighttime-light Dataset of China (1984–2020) were obtained from the National Tibetan Plateau Scientific Data Center (http://www.tpdc.ac.cn/).
Тhe original spatial raster data of river network density, road density, distance to the nearest road, elevation, slope, topographic relief, GDP, population density, nighttime lighting index, proportion of construction land area, and proportion of cultivated land area for the whole Ningxia region in 2000, 2005, 2010, 2015 and 2020 were obtained by processing the above datasets. Based on the zoning of Ningxia and the accuracy of the data, a suitable 5 km × 5 km fishing grid was built, excluding the grid with null values, to obtain the final 2290 grids. The raw data were partitioned in tabular form to obtain the final data results for each impact factor as well as the raw data results for habitat quality for the period 2000–2020, with 17 categories and 85 datasets in five periods.
The habitat quality of Ningxia was classified into five levels: low level (0–0.25), lower level (0.25–0.4), moderate level (0.4–0.6), higher level (0.6–0.75), and high level (0.75–1.0) (Fig.
In terms of spatial distribution (Fig.
The results of spatial autocorrelation analysis showed (Fig.
Spatial autocorrelation global Moran’s I values of habitat quality in Ningxia from 2000–2020.
The results of spatial autocorrelation analysis of habitat quality in Ningxia from 2000 to 2020.
Combining the distribution of patches with the different habitat quality levels in Ningxia, we found that habitat quality in Ningxia was closely related to patch type and was influenced by both natural conditions and human activities. Our study found that habitat quality levels were highest in primary forest reserves that were not disturbed by human activities, where precipitation, temperature, topography and elevation were suitable for the survival and reproduction of organisms. In contrast, habitat quality was significantly lowest in construction sites strongly disturbed by human activities, where the climate is arid, vegetation is sparse, and land use changes are frequent, i.e., they lacked the basic conditions needed to meet biological survival. In addition, although cultivated land is used as an artificial landscape, it possesses a moderate level of habitat maintenance function, and the habitat quality was generally categorised at the moderate level. Nature reserves concentrate the most fully functional ecosystems, which are crucial for protecting habitat quality and improving biodiversity levels. By identifying key areas and delineating priority protection areas, it will further contribute to the stability and improvement of regional biodiversity levels.
In terms of different levels of habitat quality (Fig.
Dynamic changes in the area proportion of patches with different levels of habitat quality in different periods in Ningxia from 2000 to 2020.
The spatial variation in habitat quality in Ningxia was divided into five classes: significantly decreasing (-1– -0.5), slightly decreasing (-0.5–-0.25), remaining stable (-0.25–0.25), slightly increasing (0.25–0.5), and significantly increasing (0.5–1) (Fig.
Spatial distribution of habitat quality and land use change in Ningxia in different periods from 2000 to 2020.
The analysis of habitat quality in Ningxia showed (Fig.
First, the analysis of 16 driving factors using Pearson’s method found that the R2 values for 2000–2020 (Fig.
Relative sum of coefficients of Pearson correlation analysis of driving factors from 2000–2020.
A comparative analysis (Table
Year | AIC | AICc | R2 | Adj R2 | ||||
---|---|---|---|---|---|---|---|---|
OLS | GWR | OLS | GWR | OLS | GWR | OLS | GWR | |
2000 | -2,818.34 | -4,365.10 | -2,818.02 | -3,060.87 | 0.327 | 0.735 | 0.322 | 0.692 |
2005 | -2,754.45 | -4,436.45 | -2,754.14 | -2,542.82 | 0.312 | 0.779 | 0.307 | 0.721 |
2010 | -2,829.25 | -4,302.96 | -2,828.93 | -2,402.95 | 0.325 | 0.762 | 0.320 | 0.700 |
2015 | -2,832.13 | -4,425.03 | -2,831.81 | -2,525.42 | 0.333 | 0.777 | 0.328 | 0.719 |
2020 | -2,198.45 | -2,263.94 | -2,198.14 | -1,769.53 | 0.121 | 0.202 | 0.114 | 0.158 |
Results of spatial autocorrelation analysis of OLS regression residuals for habitat quality in Ningxia, 2000–2020.
The results of GWR analysis showed (Table
GWR regression coefficient values of habitat quality in Ningxia from 2000 to 2020.
Variable | 2000 | 2005 | 2010 | 2015 | 2020 | Relative sum of coefficients |
---|---|---|---|---|---|---|
Intercept | 0.041 | 0.025 | 0.121 | 0.163 | 0.498 | 0.849 |
DRA | 0.007 | 0.002 | 0.007 | 0.005 | 0.002 | 0.023 |
DRN | 0.003 | 0.002 | 0.002 | 0.002 | 0.004 | 0.014 |
FVC | 0.431 | 0.392 | 0.419 | 0.256 | 0.267 | 1.765 |
GDP | 0.002 | -0.001 | 0.000 | -0.002 | 0.000 | -0.001 |
PCL | -0.687 | -0.733 | -0.687 | -0.674 | -0.479 | -3.260 |
MPA | 0.002 | 0.002 | 0.001 | 0.001 | 0.002 | 0.009 |
NLI | -0.061 | -0.054 | -0.059 | -0.010 | 0.000 | -0.184 |
CLP | -0.269 | -0.356 | -0.322 | -0.327 | -0.139 | -1.413 |
POP | 0.001 | 0.004 | 0.001 | 0.010 | 0.000 | 0.016 |
RND | -0.002 | -0.002 | -0.001 | 0.000 | 0.004 | 0.000 |
SMC | 0.324 | 0.097 | 0.116 | 0.089 | -0.008 | 0.619 |
GWR regression coefficients of the main driving factors of habitat quality in Ningxia, 2000–2020.
From the local R2 distribution map of Ningxia (Fig.
Local R2 distribution of GWR regressions of the driving factors of habitat quality in Ningxia from 2000 to 2020.
Selecting the spatial distribution of the GWR regression coefficients of the main driving factors of habitat quality in 2020 as an example, spatially (Fig.
We conclude that the distribution and evolution of habitat quality in Ningxia were mainly driven by fractional vegetation cover, soil moisture content, cultivated land expansion, and construction land expansion, where high vegetation cover and soil moisture content were suitable for biological habitats; in contrast, cultivated land and construction land expansion reduced habitat suitability. The habitat quality of forestland, grassland, water area and some cultivated land in Ningxia was high, and these patches were in good condition as ecological source land and were far from human activity areas, so they were less disturbed by resource development and utilization. The habitat quality of areas such as urban land, which had a high intensity of human activities, was obviously extremely low. The relationships between soil moisture content, some cultivated land, pasture land and habitat quality were more specific. On the one hand, higher soil water content in the natural state means lush vegetation, and the expansion of cultivated land is not conducive to habitat maintenance. However, on the other hand, due to the construction of artificial cultivated land and artificial wetland, the investment of human and material resources, green funds and ecological technology can maintain the fragile habitat to a certain extent. Therefore, there is uncertainty regarding the role of factors such as cultivated land and soil water content on habitat quality. In response to the weak natural foundation, from 2000 to 2020, Ningxia continuously improved its vegetation cover through the project of returning farmland to forest and grass, and the level of habitat quality in nature reserves such as Liupanshan and Luoshan increased significantly. Due to frequent industrial and agricultural activities such as food production and mineral extraction, the habitat quality fluctuated in some areas of Ningxia over the course of 20 years, and the results showed a decrease in habitat function. In conclusion, urban and cultivated land expansion are the most critical factors reducing habitat suitability in Ningxia, and protecting and utilizing grassland, vegetation, wetland and other ecosystems can effectively improve habitat suitability in Ningxia.
In addition, although other factors, such as topographic relief, had insufficient explanatory power for habitat quality in Ningxia, related studies have shown that rainfall, slope, elevation, and temperature are important conditions that influence the distribution and ecological niche of organisms within small-scale habitats (
GWR modelling can fully reflect the spatial non-smoothness of the region and select the optimal spatial weights in combination with spatial heterogeneity; the results have higher accuracy and credibility than Pearson correlation analysis and OLS regression for exploring the role of driving factors at large spatial and temporal scales. Although, the results are consistent with the trend of habitat quality changes in Ningxia over the past 20 years. However, some studies have shown that GWR is essentially a one-dimensional linear regression with parameters that fail to consider multivariate and correlational settings (
Ningxia is a typical ecologically fragile area with relatively poor natural foundations, and the habitat quality is at an intermediate level with a wide scope for improvement. This study explored the driving effects of habitat quality in Ningxia based on 16 physical geographic, economic and social factors and found that habitat quality tended to be higher in areas with higher vegetation cover and lower in patches with a high proportion of construction land and cultivated land. The results demonstrate that for ecologically fragile areas with similar characteristics to Ningxia’s ecological environment, enhancing vegetation cover can effectively improve habitat structure and function. For ecologically fragile areas, poor conditions such as low precipitation, loose soils, and low biodiversity, coupled with the frequent use of natural resources due to economic development, have led to further anthropogenic damage to the already fragile habitats. Ecologically fragile areas often lack biologically beneficial ecological factors, and due to the harsh natural conditions and prominent human-land conflicts, humans must sacrifice habitat quality in exchange for improved well-being, thus leading to a vicious circle of economic and social development and ecosystem decline in ecologically fragile areas (
In this study, we considered 16 factors that are critical for influencing biodiversity levels in ecologically fragile areas, and these factors fully reflected the natural climatic conditions and human activity disturbances in ecologically fragile areas. The results can be used as a reference for the conservation of ecosystems in other ecologically fragile areas internationally. In the future, studies on biodiversity conservation and habitat quality in ecologically fragile areas should combine model simulations and biodiversity field surveys to summarize the distribution and change characteristics of habitat quality over a long time series. It is also important to understand the habitats of specific species from the key areas of habitat quality maintenance, such as nature reserves and ecological functional areas, which will give more full play to the natural stability (resistance and resilience) and human maintenance of the habitat systems in ecologically fragile areas (
Global changes such as climate change and cultivated land expansion have increased the instability of ecosystems in ecologically fragile areas (
This study evaluated the habitat quality of Ningxia from 2000 to 2020 based on the InVEST model, analysed the spatial and temporal patterns and changes during the 20-year period, and explored the role of driving factors on habitat quality using correlation analysis, the OLS model, and the GWR model in combination with 16 physical-geo-socioeconomic factors. The main results of this study are as follows:
We appreciate the constructive comments and suggestions from the reviewers that helped improve the quality of this manuscript.
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
No ethical statement was reported.
This research was funded by the National Natural Science Foundation of China (Grant Number 41871196).
H.H. constructed the concept and overall framework of the research and provided the necessary funding sources and other funding for the research; D.W. collected and sorted out the research data and designed and visualized the charting of the research results; L.S. and H.L. helped D.W., to skillfully use relevant software and charts; D.W., has written and reviewed the first draft, and Y.L. has given great creativity in polishing and improving the article; H.H., L.S., H.L., and Y.L. have all made great contributions to the writing, revision, editing of articles and the management, investigation and implementation of projects. All authors have read and agreed to the published version of the manuscript.
Ding Wang https://orcid.org/0000-0003-1748-8383
Haiguang Hao https://orcid.org/0000-0003-3726-7254
Hao Liu https://orcid.org/0000-0002-1495-2120
Lihui Sun https://orcid.org/0000-0001-6380-8232
Yuyang Li https://orcid.org/0000-0001-6352-271X
Not applicable.