Luxury and legacy effects on urban biodiversity, vegetation cover and ecosystem services

Urban green spaces (UGS) are crucial for urban residents' well-being, providing various ecosystem services (ES) like climate regulation, air purification, and recreational opportunities. Traditional ecological research often focuses on climate and natural factors, but socio-economic factors are increasingly recognized as key drivers of urban biodiversity patterns. Higher socio-economic status residents have more resources to invest in vegetation and influence urban planning decisions, leading to a "luxury effect" where wealthier areas tend to have higher biodiversity. However, the spatial distribution of vegetation and biodiversity is also influenced by the "legacy effect" – historical land use policies and management practices. Older neighborhoods often exhibit higher plant diversity due to longer successional times and varied management strategies. This study examines how luxury and legacy effects influence the spatial distribution of vegetation cover, biodiversity, and regulating ES in Vitoria-Gasteiz, a mid-sized European city with a history of greening initiatives. The research aims to test the luxury and legacy hypotheses by analyzing the relationship between high educational attainment (proxy for wealth), neighborhood age, biodiversity, vegetation cover, and regulating ES, while considering other factors like population density and habitat quality.

Existing literature highlights the significant role of socio-economic factors in shaping urban biodiversity. The "luxury effect" is well-documented, showing a positive correlation between wealth (often proxied by income) and biodiversity. Studies have observed this pattern across various taxa, including plants, birds, and mammals. However, the use of income as a sole indicator of socio-economic status is debated, with some suggesting that education may be a more comprehensive proxy, capturing a broader range of socioeconomic variation. Additionally, the "legacy effect" emphasizes the lasting influence of past land-use policies and management practices on current vegetation and biodiversity patterns. Older neighborhoods, due to longer development times and historical management choices, might exhibit higher diversity. Studies on urban green cover inequalities using remote sensing data further support the influence of socio-economic factors on vegetation distribution. The interaction between luxury and legacy effects is complex and requires further investigation, particularly concerning the provision of ES in urban landscapes. There's a need for studies that integrate multiple factors and their interactions for a more holistic understanding of urban socio-ecological systems.

This study utilized a mixed-methods approach combining remote sensing, biodiversity datasets, and socio-demographic variables at the neighborhood level (n=28) in Vitoria-Gasteiz. Biodiversity was assessed using tree and bird species richness data from city council inventories and a bird census. Vegetation cover was determined using a Google Earth Engine (GEE) Random Forest classifier on Sentinel-2 imagery, differentiating between herbaceous and canopy cover. Socio-economic status was proxied by the percentage of residents with high educational attainment. A neighborhood development age index was created using historical construction data. Regulating ecosystem services (ES) were quantified using the i-Tree Eco software, focusing on transpiration, avoided runoff, pollution removal, and carbon sequestration. Generalized linear models (GLMs) were employed to analyze the relationships between the variables, testing for direct and interactive effects. Spatial autocorrelation was assessed using Moran's I. Data analysis was performed using R, and land cover classification using Google Earth Engine. i-Tree Eco was used to quantify ecosystem services.

The study found strong evidence supporting the luxury effect, with higher educational attainment positively correlated with urban biodiversity (R² = 0.25, p < 0.01). This effect was amplified in neighborhoods with higher habitat quality. Conversely, an inverse legacy effect was observed, with biodiversity negatively associated with neighborhood age (R² = 0.22, p < 0.01), likely due to more recent management strategies prioritizing biodiversity in green spaces. Vegetation cover showed no significant relationship with educational attainment but was positively correlated with habitat quality and negatively correlated with population density. A legacy effect was observed, with older neighborhoods exhibiting lower vegetation cover, particularly in denser areas. Regulating ecosystem services (ES), aggregated into a single index, were not directly correlated with educational attainment or neighborhood age alone. However, a legacy effect mediated by vegetation cover was evident; older neighborhoods with higher vegetation cover provided more regulating ES (R² = 0.57, p < 0.001). Population density negatively affected biodiversity and amplified the negative legacy effects on biodiversity and vegetation cover.

The findings confirm the influence of socio-economic factors (luxury effect) on urban biodiversity, while highlighting the significant role of historical management practices and population density (legacy effects) on vegetation cover and ecosystem service provision. The lack of a direct relationship between educational attainment and vegetation cover suggests that wealthier neighborhoods don't necessarily have more vegetation, but rather different types of vegetation that support higher biodiversity. The negative impact of population density on biodiversity emphasizes the importance of considering spatial constraints when planning green infrastructure. The interaction between legacy effects and vegetation cover in regulating ES provision highlights the long-term consequences of past management decisions. These findings underscore the complex interplay between socio-economic and biophysical factors in shaping urban ecosystems and the need to consider both luxury and legacy effects in urban planning for a more equitable distribution of UGS and their associated benefits.

This study provides crucial insights into the luxury and legacy effects on urban biodiversity, vegetation, and ecosystem services. The results emphasize the importance of considering socio-economic factors, historical management practices, and population density in urban planning. Future research could focus on exploring the specific mechanisms driving the observed patterns, investigating the role of different tree species in ES provision, and examining the effectiveness of various green infrastructure strategies in addressing environmental justice concerns. Understanding these complex interactions is essential for developing sustainable and equitable urban greening strategies that enhance both biodiversity and human well-being.

The study is limited by its focus on a single city, potentially limiting the generalizability of the findings. The use of educational attainment as a proxy for socio-economic status might not fully capture the complexities of wealth distribution. The analysis is correlative and cannot establish direct causal relationships between variables. Data on private green spaces and their management were not included, which might affect the interpretation of luxury effects on vegetation cover. Future studies should address these limitations to provide a more complete understanding of the complex factors shaping urban ecosystems.