Habitat loss and urbanisation in the tropics have been recognised as major drivers of species extinctions. Concurrently, novel habitats such as urban parks have been shown to be important as habitats and stepping stones in urban ecosystems around the world. However, few studies have assessed long-term patterns of species extinctions and discoveries in response to these drivers in the tropics. We know little about long-term persistence and utility of novel habitats in tropical urban ecosystems. In this study, we produced an updated and exhaustive butterfly checklist of species recorded from Singapore till December 2017 to investigate trends in butterfly extirpations (local extinctions), discoveries (new country records) and rediscoveries and how these relate to land use change in 28 years (1990–2017) in Singapore. Up to 144 butterfly species were identified to be extirpated in Singapore by 1990. From 1990–2017, an additional nine butterfly extirpations have potentially occurred, which suggests a maximum of 153 butterfly extirpations to date. The rate of extirpations between 1990 to 2017 (< 0.33 extirpations per year) was much lower than the rate of extirpations between 1926 to 1989 (> 1.52 extirpations per year). The majority of potentially extirpated butterflies between 1990 to 2017 were species restricted to mature forests. Over this period, 51 new species were discovered, while 65 species were rediscovered, which collectively represent 24% of the total and 35% of the extant butterfly fauna of Singapore. Interestingly, 33% of discovered species were only observed in degraded secondary forests or urban parks in Singapore, the former maturing with age and the latter having increased in area during the same time period. We hypothesise that the current slowdown in butterfly extirpations may be representative of habitat recovery and/or improved habitat connectivity, lower undetected extirpations, and/or lengthening of extinction debts. A slowdown in extirpations and an increased utilisation of novel habitats by discovered species present a window of conservation opportunity to restore native habitats and increase habitat connectivity among existing patches of managed vegetation.

Habitat loss and urbanisation in the tropics have been recognised as major drivers of species extinctions. Concurrently, novel habitats such as urban parks have been shown to be important as habitats and stepping stones in urban ecosystems around the world. However, few studies have assessed long-term patterns of species extinctions and discoveries in response to these drivers in the tropics. We know little about long-term persistence and utility of novel habitats in tropical urban ecosystems. In this study, we produced an updated and exhaustive butterfly checklist of species recorded from Singapore till December 2017 to investigate trends in butterfly extirpations (local extinctions), discoveries (new country records) and rediscoveries and how these relate to land use change in 28 years (1990–2017) in Singapore. Up to 144 butterfly species were identified to be extirpated in Singapore by 1990. From 1990–2017, an additional nine butterfly extirpations have potentially occurred, which suggests a maximum of 153 butterfly extirpations to date. The rate of extirpations between 1990 to 2017 (< 0.33 extirpations per year) was much lower than the rate of extirpations between 1926 to 1989 (> 1.52 extirpations per year). The majority of potentially extirpated butterflies between 1990 to 2017 were species restricted to mature forests. Over this period, 51 new species were discovered, while 65 species were rediscovered, which collectively represent 24% of the total and 35% of the extant butterfly fauna of Singapore. Interestingly, 33% of discovered species were only observed in degraded secondary forests or urban parks in Singapore, the former maturing with age and the latter having increased in area during the same time period. We hypothesise that the current slowdown in butterfly extirpations may be representative of habitat recovery and/or improved habitat connectivity, lower undetected extirpations, and/or lengthening of extinction debts. A slowdown in extirpations and an increased utilisation of novel habitats by discovered species present a window of conservation opportunity to restore native habitats and increase habitat connectivity among existing patches of managed vegetation

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