In conjunction with Earth Day and World Biodiversity Day 2008, NParks is holding a series of biodiversity talks on natural habitats in Singapore. All are free and most are at the Botanic Gardens Botany Centre (near the entrance opposite Gleneagles Hospital):
(Click here to see full event list)
Also, budak pointed me to this book: The World Without Us. Am going to try to get my hands on a copy.