An ecologist with a long-time interest in biodiversity and biogeography from local to global scales, particularly in marine and freshwater ecosystems, with applications in climate change, conservation and aquaculture.

Supervised over 60 graduate students. Published over 240 peer-reviewed papers cited over 15,000 times (H-index 60).

Played leading roles in Biodiversity Informatics through developing world databases that list and map biodiversity across land and sea, including the World Register of Marine Species (WoRMS), Ocean Biodiversity Information System (OBIS), Global Biodiversity Information Facility (GBIF), Species 2000's Catalogue of Life, and the World Register on Introduced Marine Species (WRiMS). He has been involved in the Group on Earth Observations Biodiversity Observation Network (GEO BON) since it began, co-chaired its Marine BON until 2021, and is a Lead Author in the current IPCC 6th Assessment Report.