The total number of species is not known. More than one half of the world's species live in tropical forests. About 10 million species have been identified by scientists. The Earth has many more species than it needs. More species are of no direct benefit to humans.
Some habitats have more species than others.
Biodiversity includes genetic diversity, species diversity and ecosystem diversity. Biological diversity is more threatened now than at any time in the past 65 million years. The loss of forest, wetlands, grasslands, and other habitats contributes to loss of biodiversity. Many species become extinct without ever being identified. Large plants, birds and mammals make up about half the world's species.