The National Parks Board's Floral and Fauna Web is the definitive place to search for biodiversity in Singapore. Go to: https://florafaunaweb.nparks.gov.sg/
Listed below are a selection of government agencies/related information in Singapore. To explore a full list of other ministries/agencies, click here. For research on government related/ historical information (government records, building plans, maps, speeches etc) in Singapore, you may also wish to look at the National Archives of Singapore's Archives Online database.
Other than the various international NGOs with offices here, there are also several Singapore/homegrown NGOs involved in environmental issues etc. Below are links to a few selected groups.