The ecological role and potential impact of an alien tree highly attractive to native nectar-feeding birds in urban areas

Alien plants may provide considerable benefits to biodiversity in urban areas while showing low to moderate risk of negative impacts. Here, we evaluated the ecological role of the alien tree Bombax ceiba when interacting with nectar-feeding birds, including its potential for negative impacts as an invasive plant in an urban area in Brazil. At the community level, network analysis of 70 bird species interacting with flowers from 73 plant species showed B. ceiba to be one of the few hub plant species, indicating its importance as a nectar resource for urban birds. Specifically, B. ceiba flowers attracted 38 bird species with different habits (feeding guilds and habitat requirements), most of which fed on nectar, while some also consumed floral parts. On the other hand, the semiquantitative risk assessment for B. ceiba regarding potential negative impacts on native species and ecosystems indicated only a moderate risk, suggesting an overall benefit of keeping this tree species in the urban landscape. In this context, we highlight that the function, not only the origin of a species, may be used to plan biophilic cities through urban greening. Moreover, possible suppression of alien plants should consider the ecological role these species play in urban areas. Given that proper assessment of risk factors is carried out, urban afforestation with some alien plant species can promote biodiversity and ecosystem services by providing key resources during food scarcity for the fauna.

Automated summary

Alien plants can have considerable benefits to biodiversity in urban areas with low to moderate risk of negative impacts. A study in an urban area in Brazil evaluated the ecological role of the alien tree Bombax ceiba in interacting with nectar-feeding birds and found it to be an important nectar resource for urban birds. Although there is a moderate risk of negative impacts on native species and ecosystems, keeping this tree species in the urban landscape can provide overall benefits.