According to the International Union for Conservation of Nature (IUCN) 2004 report, the total number of plant and animal species that have been successfully described and documented on Earth is slightly more than 1.5 million. While global biodiversity is estimated by scientists to be much higher-with conservative estimates like those of Robert May placing the total number of species at approximately 7 million-the officially recorded count in 2004 was capped near this 1.5 million mark