Maintenance-Weighted Biodiversity Return in Singapore Urban Green Spaces: Evidence from Parks and Streetscapes

Abstract

Singapore’s urban green spaces should promote biodiversity and yet be safe, legible, and cheap to maintain. Rapid vegetation growth and regular pruning are likely to reduce insect and bird faunas through reduced flowering, litter, understory, and nesting structures within humid tropical urban green spaces. This paper assesses 13 Singapore urban green spaces comprising 7 parks and 6 streetscapes and determines whether sites having high faunal capacity also generate high biodiversity return when subject to light maintenance activities. Assessment was based on data regarding vegetation density, maintenance class, planted vs. spontaneous vegetation, species richness, Shannon diversity, probable species numbers, and cross-taxon performance for aculeate hymenoptera, butterflies, and birds. Four calculated metrics were considered: composite faunal capacity, low-input biodiversity return, unfulfilled species numbers, and cross-taxon performance. While parks recorded high average composite faunal capacity values (0.765), streetscapes recorded high values of spontaneous vegetation (0.602). Sites maintained under low maintenance conditions produced the greatest biodiversity return, at 0.577, against medium maintenance levels (0.274) and high maintenance conditions (0.152). Current return was greatest for Tampines Eco-Green (0.429), Chuan Lane Park (0.368), NUS Ventus (0.291), and Admiralty Road West (0.241), while those showing low current return included West Coast Park, Jurong Central Park, and Sembawang Hot Spring Park, all of which exhibited greater maintenance release priority. Results indicate that biodiversity amounts and biodiversity returns give contrasting planning signals for tropical urban green spaces.