Objective Allergic diseases are immune-related diseases, and their incidence rate is increasing. The decrease in the contact between natural environment and biodiversity caused by the decline of global ecological environment quality is an important factorfor their high incidence. As an important part of the ecosystem, green space is an important carrier facilitating contact between natural environment and biodiversity, and its impact on allergic diseases is increasingly concerned. A deep understanding of the relationship between green space biodiversity and allergic diseases can not only provide a theoretical basis for exploring the relationship between cities, ecology, and health in the process of rapid urbanization, but also provide a practical approach for improving the ecological environment quality of national land and improving health service functions.
Methods Based on literature retrieved from Web of Science and PubMed up to 2025, this review selected empirical studies examining the relationship between green space, its biodiversity, and allergic diseases. A systematic synthesis was conducted to summarize research methods, findings, and underlying mechanisms concerning the impact of green space and its biodiversity on allergic diseases.
Results Firstly, in terms of research methods, a total of 16 studies used cohort analysis, 12 studies used cross-sectional analysis, and 2 studies used case-control designs. The research subjects were mainly children (26 studies). The spatial scale of research mainly focuses on urban and residential areas. In addition, two studies were conducted on townships. Spatial units included family or school buffer zones (26 items), census areas (2 items), and administrative units (2 items). Green space and biodiversity data mainly came from remote sensing satellites or departmental data. The research areas are concentrated in Europe (14 items), the Americas (9 items), Oceania (2 items) and Asia (5 items), including 2 studies in Mainland China and 2 items in Taiwan, China. These documents reveal a correlation between green space biodiversity and the risk of allergic diseases. Cohort studies, using long-term time-series data, can reveal the cumulative effects of biodiversity on allergic diseases to some extent. However, such studies mainly focus on the macro-level supply characteristics of green spaces, and the measurement of biodiversity is still relatively coarse. Moreover, there is limited empirical evidence on the impact of microbial diversity as the mediating factor. Cross-sectional studies can reveal the differential effects of different indicators on allergic diseases and analyze the comprehensive impacts of demographic, socioeconomic, and material environmental factors on allergic diseases by incorporating more refined green space biodiversity indicators and more comprehensive control variables. However, they cannot distinguish causal temporal relationships, resulting in cumulative or lagged effects of green spaces on health that cannot be verified through data from a single time point. Case-control studies have time and economic cost advantages compared to cohort studies. However, current case-control studies have included only availability and accessibility indicators that reflect the overall characteristics of green spaces, and have not provided clear or specific measurements of green space biodiversity. Secondly, the analysis of the impact results shows that there are certain differences in the results obtained from existing studies. Indicators related to plant diversity and tree species composition are associated with a reduced risk of allergic diseases, while indicators related to grasslands, coniferous trees, and non-native plants are associated with an increased risk of allergic diseases. However, there are significant differences in the research conclusions of indicators reflecting overall supply characteristics. The inconsistency of research conclusions may mainly be caused by differences in research design, exposure assessment, control variables, and geographical regions. Thirdly, in terms of influencing mechanisms, the impact mechanism of green space biodiversity on allergic diseases may stem from its key role in maintaining ecological community stability and preventing species imbalance. The existing theoretical hypothesis has jointly revealed the basic relationship between green space biodiversity and allergic diseases: under the background of urbanization, the environmental and lifestyle changes, the reduction of macro-biodiversity and of human contact with green space and other natural environments and biodiversity, which led to the reduction of microbial diversity contact level, hinders immune regulation circuits, and leads to a sharp rise in the incidence rate of allergic diseases; Appropriate environmental microbial exposure can be achieved by restoring urban green spaces, potentially reducing the incidence of allergic diseases may be reduced. However, existing theoretical hypotheses and related empirical research on the measurement, impact pathways, and mechanisms of green space biodiversity on allergic diseases are still relatively broad. The role of green space biodiversity in maintaining community species balance, preventing microbial dysbiosis, and inhibiting single species dominance, as well as the empirical verification of the mediating role of microbial diversity between macro biodiversity and allergic diseases, are not sufficient. Further empirical research is needed to verify and improve the existing theoretical system.
Conclusion The existing research on the impact of green space biodiversity on allergic diseases still has limitations such as coarse characterization of green space biodiversity, lack of consistency in quantitative methods, insufficient exploration of the regulatory effects of green space biodiversity on species balance, and insufficient exploration of the impact mechanism mediated by microbial diversity. Future research needs to focus on the differential impact of fine-grained green space biodiversity indicators on allergic diseases based on a unified element indicator measurement method; 2) Combining experimental research to explore in depth the regulatory effects of green space biodiversity on species balance; 2) focusing on the intrinsic mechanisms of microbial diversity; 3) exploring how environmental microorganisms (e.g., air and soil microorganisms) and human microorganisms (such as skin and respiratory microorganisms) mediate the impact of green space biodiversity on allergic diseases, and revealing the transmission pathways from macro-biodiversity to microbial communities, thereby providing scientific basis for green space biodiversity management and ecological quality improvement.
DownLoad: