The diversity of life on Earth—which provides vital services to humanity (1)—stems from the difference between rates of evolutionary diversification and extinction. Human activities have shifted the balance (2): Species extinction rates are an estimated 1000 times the “background” rate (3) and could increase to 10,000 times the background rate should species threatened with extinction succumb to pressures they face (4). Reversing these trends is a focus of the Convention on Biological Diversity's 2020 Strategic Plan for Biodiversity and its 20 Aichi Targets and is explicitly incorporated into the United Nations' 2030 Agenda for Sustainable Development and its 17 Sustainable Development Goals (SDGs). We identify major gaps in data available for assessing global biodiversity threats and suggest mechanisms for closing them.