Spatiotemporal ecological quality assessment of metropolitan cities: a case study of central Iran

Lake shrinkage-induced terrestrial ecological environmental quality degradation in a semiarid lake basin

Lake water environmental problems caused by lake shrinkage in semiarid zones have attracted widespread attention, but few studies have quantified the impact of lake shrinkage on the terrestrial ecological environmental quality of watersheds. In this study, remote sensing image inversion, digital elevation modeling, and statistical analysis were applied to explore the impact of Lake Daihai shrinkage on the terrestrial ecological environmental quality of its receding water areas from 1986 to 2019. The results showed that the area of Lake Daihai shrank from 170.7 km2 in 1961 to 50.67 km2 in 2019, a shrinkage of 70.32%. The average annual shrinkage was 2.07 km2 during the period of 1986-2019 (r = -0.99, p < 0.01). The main conclusions of this study are as follows: The mean remote sensing ecological index values decreased significantly from 0.628 in 1986 to 0.441 in 2019 (r = -0.78, p < 0.05), which means that the terrestrial ecological environmental quality of the water receding area degraded from a good grade to a moderate grade. The increase in water use by residents in the basin was an important reason for the shrinkage of Lake Dahai. Approximately 90% of the wetlands in the receding water areas formed after the shrinkage of Lake Daihai were converted to farmland by local residents, which significantly degraded the terrestrial ecological environmental quality of these areas from good to moderate grade over the 34-year period (r = -0.83, p < 0.05). Correlation analysis indicated that the remote sensing ecological index was positively correlated with lake area (r = 0.85, p < 0.01). The results indicate that steps should be taken to decrease the impact of human activities on the terrestrial ecological environmental quality of lake basins in semiarid zones.

Measuring the extent and impact of urban expansion in an agricultural-urbanized landscape in Central Iran

The unplanned urban expansion is a major environmental challenge in Iran resulting in vast degradation of agricultural lands. Focusing on an agricultural-urbanized landscape in Central Iran, the spatial pattern of built-up expansion was assessed from Landsat data processed in 1992 (TM), 2002 (ETM+), 2012 (TM), and 2022 (OLI). Multi-year crop NDVI was also used as a proxy for cropland suitability to assess the intensity of the urban growth impact. Results showed that (1) the area of built-up surfaces increased almost up to double than that of 1992 and passed 36% (413.42 km2) by 2022, (2) the region experienced a coalescence-diffusion transition phase with decreasing spatial connectivity of newly developed patches with old ones, (3) the most suitable croplands were lost in the middle period (2002-2012) when urban patches started to diffuse, and (4) a significantly positive spatial (Spearman's) relationship (r (22100) = 0.181, p = 0.000) was found between the area and quality of croplands which further highlights the high importance of cropland protection in the region.

Spatiotemporal changes of ecological environment quality and climate drivers in Zoige Plateau

Ecological environment is the essential material basis of human survival and connects regional economy with socially sustainable development. However, climate changes characterized by global climate warming have caused a series of ecological environmental problems in recent years. Few studies have discussed various climate factors affecting the ecological environment, and the spatial non-stationary effects of different climate factors on the ecological environment are still unclear. Dynamically monitoring ecological environment changes in fragile areas and identifying its climate-driving mechanism are essential for ecological protection and environmental repair. Taking Zoige Plateau as a case, this paper simulated the eco-environmental quality during 1987-2020 using remote sensing data, utilized Geodetector method to identify the contributions of various climate drivers to ecological environment quality, and then adopted the Geographically Weighted Regression model to explore the spatial non-stationary impacts of climate factors on ecological environment quality. The results showed that the ecological quality in the middle regions of the Zoige Plateau was slightly better than in the surrounding marginal areas. For the whole area of Zoige Plateau, the average ecological environment quality index was 54.92, 53.99, 56.17, 57.88, 63.44, 56.93, 59.43, and 59.76 in 1987, 1992, 1997, 2001, 2006, 2013, 2016 and 2020, respectively, which indicated that eco-environmental quality witnessed several fluctuations during the study period but showed a generally increasing trend. Among five climate factors, the temperature was the dominant climate factor affecting the ecological environment quality (q value: 0.11-0.19), sunshine duration (0.03-0.17), wind speed (0.03-0.11), and precipitation (0.03-0.08) were the main climate drivers, while the explanatory power of relative humidity to ecological environment quality was relatively small. Such various climate factors impacting the ecological environment quality demonstrated distinct spatial non-stationary and the range of driving impact varied with time. Temperature, sunshine duration, wind speed, and relative humidity promoted ecological environment quality in most regions (regression coefficients > 0), while precipitation mainly had a negative inhibitory impact (regression coefficients < 0). Meanwhile, the greater impacts of these five climate factors were concentrated in high-elevation regions of the south and west or the northern areas. The appropriate enhancement of climate warming and air humidity was beneficial to the improvement of the ecological environment, but the excessive precipitation would result in landslides and exhibit inhibition of vegetation growth. Therefore, selecting cold-tolerant herbs and shrubs, and strengthening climate monitoring and early warning systems (such as drought and excessive precipitation) are essential for ecological restoration.

Spatiotemporal Change of Eco-Environmental Quality in the Oasis City and Its Correlation with Urbanization Based on RSEI: A Case Study of Urumqi, China

As an important node city of “The Belt and Road” strategy, Urumqi has a non-negligible impact on the ecological environment in the process of rapid development. It is of great significance to understand the coupling and coordination between urbanization and the ecological environment for regional sustainable development. However, previous studies on the coupling coordination degree (CCD) model of urbanization and ecological environment are limited, and they ignore the endogenous relationship between the two. Therefore, this study aims to introduce an econometric model, the panel vector autoregression model (PVAR), to further explore the relationship between them and the influencing mechanism. Firstly, urbanization and ecological environment were evaluated objectively by the comprehensive nighttime light index (CNLI) and remote sensing ecological index (RSEI), respectively. Then, the coupling coordination degree of urbanization and the ecological environment were evaluated comprehensively by a typical coupling coordination degree model. Finally, the PVAR model is used to analyze the interaction between the two systems and the mechanism of action. The results showed that: (1) in the recent 25 years, the mean value of RSEI in Urumqi decreased gradually, and the overall ecological environment deteriorated, but the differences among districts and counties were still significant; (2) the urbanization level of Urumqi is on the rise, while UC, DBC(B), and MD have the highest increase in CNLI although they are at a low level; and (3) in the interactive relationship between urbanization and the ecological environment, the development of Urumqi’s ecological environment is mainly affected by its development inertia, and the development of urbanization is limited by the ecological environment. This study fills the gap in the study of the interaction mechanism between urbanization and the ecological environment and provides a new perspective for the study of sustainable urban development worldwide.

A Remote-Sensing Ecological Index Approach for Restoration Assessment of Rare-Earth Elements Mining

In order to meet the requirements for comprehensive and multidimensional generalization of ecological management effectiveness evaluation indexes in the context of ecological restoration advocating comprehensive management by multiple means, this paper explores the rationality of using RSEI as an ecological management effectiveness evaluation index to adapt to the systematic transformation of the management goal of abandoned mine restoration from ecological restoration to regional socioeconomic sustainable development. Based on Landsat-8 image data, the remote sensing ecological index (RSEI) was used to evaluate the dynamic changes and spatial and temporal differences of the ecological environment in the study area under the long-term multimeans comprehensive management. The RSEI is suitable for evaluating the effectiveness of comprehensive ecological management in mining areas with a large amount of bare soil. The regional RSEI mean value increased by 0.029 in the early stage and 0.051 in the later stage by fragmentation management, indicating a better effect of multimeans comprehensive management. The remote sensing ecological index can objectively reflect the difference of spatial distribution characteristics of ecological environment in the four “Ecological+” governance regions. It can both objectively reflect the ecological status of the study area and reflect the differentiated spatial distribution characteristics of the ecological environment in different treatment areas, which is of long-term practical significance to the ecological construction of the study area. This study provides a theoretical reference for ecological assessment of complex situation under difficult site conditions.

RSEI-Based Modeling of Ecological Security and Its Spatial Impacts on Soil Quality: A Case Study of Dayu, China

Rapid urbanization and industrialization have brought serious threats to urban ecological security, which refers to the health and integrity of urban ecosystems. By collecting multi-source data in the modeling of the ecological security pattern, we used the remote sensing ecological index (RSEI) to identify the ecological sources (ESOs), and applied five indicators to construct the resistance surface, including land-use type, normalized vegetation index (NDVI), normalized building index (NDBI), slope, and digital elevation model (DEM). Based on the ESOs and ecological resistance surface, we calculated the cost distance of each pixel to the nearest ESO using the minimum cumulative resistance model. With the natural breakpoint method, we classified the cost distance into five levels, and constructed the ecological security pattern of Dayu. In Dayu, there were areas of at least 40% with stable ecological security. We identified 39, 31, and 43 ESOs of Dayu in 2012, 2016, and 2020, respectively. During 2012 to 2016, the number of medium ESOs decreased from 16 to 5, and the number of small ESOs increased from 13 to 26. From 2016 to 2020, the number of medium-sized ESOs increased from 5 to 18, and the number of small-sized ESOs decreased from 26 to 20. The percentage of the Level-5 (the worst) ecological security was 5.84% in 2012, 6.80% in 2016, and 4.42% in 2020. The ecological security was negatively correlated with the intensity of the human activities and varied significantly in different towns. The soil quality was positively consistent with the ecological security, and the urbanization caused damage to the soil security. A few suggestions were finally provided for decision-makers to improve the ecological environments and the soil quality.