Response of vegetation phenology to urbanization in urban agglomeration areas: A dynamic urban-rural gradient perspective

Urbanization weakens vegetation resilience in the Pearl River Delta, China

Rapid urbanization has introduced increasingly complex social-ecological processes, intensifying the impacts on vegetation growth. Assessing urban vegetation resilience is critical to understanding urban vegetation growth. However, the current understanding of vegetation resilience in highly urbanized areas, especially regarding the influence of human activities, remains limited, constraining efforts toward sustainable urban vegetation management. In this study, we identified the spatiotemporal heterogeneity of urban vegetation resilience in the Pearl River Delta (PRD) using the lag-one autocorrelation coefficient (AC1) of the enhanced vegetation index (EVI) derived from Landsat imagery. Referring to the general conceptual framework for quantifying the impacts of urbanization on vegetation growth, we assessed the impacts of urbanization on vegetation resilience in the PRD urban agglomeration from 1998 to 2022. Results revealed that 21% of the urban area experienced one to five vegetation loss events, primarily lasting 1-2 years. Although vegetation growth was enhanced along the urbanization intensity gradient, a significant (p < 0.05) downward trend in vegetation resilience was observed, indicating that urbanization restricted the stability and sustainability of urban vegetation. By distinguishing between direct and indirect impacts, we found that the indirect impacts of urbanization on vegetation resilience gradually outweighed the direct impacts over time. Our findings further demonstrate that while intensive management can promote regreening in urban settings, maintaining the prevalent stability of urban vegetation remains challenging. These findings contribute to a better understanding of the human impact on vegetation resilience and offer significant implications for seeking directions to improve urban vegetation resilience.

Urban abiotic stressors drive changes in the foraging activity and colony growth of the black garden ant Lasius niger

Changes in habitat characteristics are known to have profound effects on biotic communities and their functional traits. In the context of an urban-rural gradient, urbanisation drastically alters abiotic characteristics, e.g., by increasing environmental temperatures and through light pollution. These abiotic changes significantly impact the functional traits of organisms, particularly insects. Furthermore, changes in habitat characteristics also drive changes in the behavioural traits of animals, allowing them to adapt and thrive in new environments. In our study, we focused on the synanthropic ant species Lasius niger as a model organism. We conducted nocturnal field observations and complemented them with laboratory experiments to investigate the influence of night warming (NW) associated with Urban Heat Islands (UHI), light pollution (ALAN), and habitat type on ant foraging behaviour. In addition, we investigated the influence of elevated temperatures on brood development and worker mortality. Our findings revealed that urban populations of L. niger were generally more active during the night compared to their rural counterparts, although the magnitude of this difference varied with specific city characteristics. In laboratory settings, higher temperatures and continuous illumination were associated with increased activity level in ants, again differing between urban and rural populations. Rural ants exhibited more locomotion compared to their urban counterparts when maintained under identical conditions, which might enable them to forage more effectively in a potentially more challenging environment. High temperatures decreased the developmental time of brood from both habitat types and increased worker mortality, although rural colonies were more strongly affected. Overall, our study provides novel insights into the influence of urban environmental stressors on the foraging activity pattern and colony development of ants. Such stressors can be important for the establishment and spread of synanthropic ant species, including invasive ones, and the biotic homogenization of anthropogenic ecosystems.

How financial clustering influences China's green development: Mechanism investigation and empirical discussion

Understanding the significance of financial clustering in the context of green development holds immense importance for China as it strives towards achieving high-quality green development. Using a balanced panel dataset encompassing China's 283 cities from 2009 to 2020, we aim to explore the impact of financial clustering on green development from both linear and nonlinear perspectives. Empirical evidence suggests that when the level of financial clustering increases by 1%, the city-level green development increases by 0.1012%. A mediation effect model certifies that there are three essential channels through which financial clustering robustly boosts green development: technical, structural and scale effects. Subsequently, a novel program handling endogeneity is designed and verifies the nonlinear nexus between financial clustering and green development. Moreover, the spatial Durbin model demonstrates that financial clustering significantly sustains local green development, despite its relatively weak spill over effects. Heterogeneity analysis presents that the promoting effect is particularly predominant in Central China, as well as in cities characterized by high levels of financial clustering and large population sizes.

Water-energy-vegetation nexus explain global geographical variation in surface urban heat island intensity

Surface urban heat island (SUHI) is a key climate risk associated with urbanization. Previous case studies have suggested that precipitation (water), radiation (energy), and vegetation have important effects on urban warming, but there is a lack of research that combines these factors to explain the global geographic variation in SUHI intensity (SUHII). Here, we utilize remotely sensed and gridded datasets to propose a new water-energy-vegetation nexus concept that explains the global geographic variation of SUHII across four climate zones and seven major regions. We found that SUHII and its frequency increase from arid zones (0.36 ± 0.15 °C) to humid zones (2.28 ± 0.10 °C), but become weaker in the extreme humid zones (2.18 ± 0.15 °C). We revealed that from semi-arid/humid to humid zones, high precipitation is often coupled with high incoming solar radiation. The increased solar radiation can directly enhance the energy in the area, leading to higher SUHII and its frequency. Although solar radiation is high in arid zones (mainly in West, Central, and South Asia), water limitation leads to sparse natural vegetation, suppressing the cooling effect in rural areas and resulting in lower SUHII. In extreme humid regions (mainly in tropical areas), incoming solar radiation tends to flatten out, which, coupled with increased vegetation as hydrothermal conditions become more favorable, leads to more latent heat and reduces the intensity of SUHI. Overall, this study offers empirical evidence that the water-energy-vegetation nexus highly explains the global geographic variation of SUHII. The results can be used by urban planners seeking optimal SUHI mitigation strategies and for climate change modeling work.