Diversity-Buffered Allergenic Leverage Analysis of Subtropical Public Gardens in Funchal

Abstract

In urban gardens, shade, culture, recreation, biodiversity and many other positive attributes are provided; yet, in addition to providing these positive traits, plants found in gardens could contribute towards increasing allergies through the release of allergenic pollen. The current paper uses DBALM in the assessment of two urban public gardens located in Funchal, Madeira: Municipal Garden and Santa Catarina Park. In particular, a direct analysis of the Index of Urban Green Zone Allergenicity (\(IUGZA\)), along with the use of threshold position, Shannon-evenness buffering, green-surface normalisation, latent biological activation, contribution concentration and replacement leverage is used. In the first place, \(IUGZA\) is 0.39 for Municipal Garden and 0.16 for Santa Catarina Park, implying that only the former exceeds the concern threshold of 0.30. In addition, the use of diversity buffering helped preserve this differentiation, since \(DBP\) is 0.257 and 0.070, correspondingly. This differentiation could not be explained through the comparison of the gardens’ areas and numbers of plant species, yet differences in trees’ evenness, contribution concentration and pressure in planted surfaces were evident. There are four plants that account for 72.54% of contribution signal, namely Ginkgo biloba, Cinnamomum camphora, Celtis australis and Araucaria columnaris. Their functional replacement would lead to decreasing \(IUGZA\) from 0.39 to 0.107, while their partial replacement would decrease this value to 0.249. Overall, Santa Catarina Park shows less realised pressure, although it has higher latent biological activation, indicating surveillance needs there, rather than broad interventions.