Sacred sites as refuges for native plant diversity in an urbanized tropical landscape

In fragmented and intensively managed remnant urban green spaces, enabling natural regeneration is crucial to sustain ecosystem functioning and associated services. Natural regeneration therefore offers an important lens into ecological resilience in human-modified landscapes. Here we present one of the most comprehensive field-based assessments of urban plant diversity in the Afrotropics, comprising over 25,000 naturally regenerating woody plant individuals of 206 species (39% native) across 329 vegetation patches in Antananarivo, Madagascar. Landscape-level native species diversity declined with greater building complexity, density and socio-economic development, whereas exotic species showed no consistent associations with determinants of urban characteristics. Native species richness was highest in ‘sacred’ forest fragments, many of which contain historic remains dating back to pre-colonial times. Notably, seven of the ten most species-rich patches were located in such sites. Our findings highlight the potentially important role of these sites in sustaining native species diversity and indicate how socio-cultural factors can present both opportunities and barriers for tropical urban conservation and restoration.