Understanding the drivers of urban plant diversity (UPD) and above ground biomass (AGB) in urbanized areas is critical for urban ecosystem services and biodiversity protection. The relationships between UPD and AGB have been investigated simultaneously. However, the drivers of UPD and AGB have been explored independently in tropical coastal areas at different time points. To fill this gap, we conducted a remote sensing interpretation, field plant plot surveys, and compiled socioeconomic and urban greening management survey data. We conducted spatial analyses to investigate the relationships among UPD and socioeconomic variables across different primary and secondary urban functional units (UFUs) in the tropical urban ecosystems of the coastal city of Haikou, China. The primary UFUs with the highest AGB were the recreation and leisure districts in 2015 and 2021. In 2015, AGB was mainly correlated with the number of herb species in undeveloped land and the districts of industry, business, recreation, and leisure. In 2021, AGB was affected primarily by the frequency of fertilizing, maintenance, and watering. Our study found that the relationship between UPD and AGB varied across time and space in Haikou. The plant diversity and AGB’s response to human activities and socioeconomics appear to have a time-lag effect. These results provide new insights in understanding how management decisions affect urban vegetation and could be used to guide future urban green space planning in Haikou.

In recent decades, the phenomenon of rapid urbanization in various parts of the world has led to a signi cant increase in PM 2.5 concentration, which has emerged as a growing social concern. In order to achieve the objective of sustainable development, the United Nations Global Sustainable Development Goals (SDGs) have established the goal of creating inclusive, safe, resilient, and sustainable cities and human habitats (SDG 11). Goal 11.6 aims to decrease the negative environmental impact per capita in cities, with an emphasis on urban air quality and waste management. However, the global distribution of PM 2.5 pollution varies due to disparities in urbanization development in different regions. The purpose of this paper is to explore the global spatial distribution and temporal variation of PM 2.5 in cities with populations greater than 300,000 from 2000 to 2020, to gain insight into the issue. The ndings indicate that PM 2.5 concentrations are expected to continue increasing as urbanization progresses, but the rate of evolution of PM 2.5 concentration varies depending on the continent, country, and city. From 2000 to 2020, PM 2.5 concentration increased signi cantly in Asia and Africa, with the majority of the increased concentrations located in Asian countries and some African countries. On the other hand, most European and American countries had lower PM 2.5 concentrations. The results of this study have the potential to inform urbanization policy formulation by providing knowledge about the spatial distribution of PM 2.5 pollution during global urbanization. Addressing the issue of PM 2.5 pollution is critical in achieving SDG 11.6 and promoting sustainable and coordinated development in cities worldwide.

Habitat fragmentation engenders a reduction in the geographic distribution of species, thereby rendering diminutive populations susceptible to extinction due to environmental, demographic, and genetic factors. Chieniodendron hainanense (henceforth C. hainanense) exemplifies a wild plant with extremely small populations (WPESP) and faces endangerment, necessitating urgent national conservation efforts. Elucidating the genetic diversity of C. hainanense is crucial for uncovering underlying mechanisms and devising protective strategies. In the present study, 35 specimens from six distinct cohort groups were genotyped utilizing genotyping-by-sequencing (GBS) and single nucleotide polymorphism (SNP) methodologies. The results indicated that C. hainanense exhibits limited genetic diversity. Observed heterozygosity within C. hainanense populations spanned from 10.79% to 14.55%, with an average value of 13.15%. The six C. hainanense populations can be categorized into two distinct groups: (1) Diaoluoshan and Baishaling, and (2) Wuzhishan, Huishan, Bawangling, and Jianfengling. The degree of genetic differentiation among C. hainanense populations is relatively weak. The observed loss of diversity can be attributed to the effects of natural selection.

Sustainable green space is essential in urban areas to maintain and improve human well-being. However, to better understand the impact of environmental and socioeconomic changes on the sustainability of tropical urban green space landscapes, work is needed to explore the patterns of plant diversity and its drivers in urban green spaces. We explore urban floristic diversity patterns based on samples from 826 urban functional units located in five cities in the tropical coastal region of China. Field surveys were conducted to obtain data on plant diversity, land use types, socioeconomic characteristics, and environmental characteristics within these units. Plant diversity within the cities varied significantly among land use types, with high-rise housing, parks and universities exhibiting higher diversity. The diversity of cultivated plants and regional economy showed significant positive correlation, while an increase in the diversity of spontaneous plants and native species was linked to building age. Management also affected plant diversity, with watering frequency being positively associated and maintenance frequency. Urban plant diversity patterns result from a combination of multiple factors. Socio-economic factors are the primary driver of the patterns of urban plant diversity, as space management and maintenance determine what can grow in different areas. The implications of the study have important practical significance for policymakers and managers in the development and management of urban green spaces more sustainably.