The disappearance and fragmentation of habitats due to human activities - deforestation and the draining of wetlands for agriculture, urbanization, and the establishment of industries - poses the greatest threat to animal and plant species.

Other threats include overexploitation (overfishing and excessively intensive hunting) and pollution. Also, non-native species introduced by humans can pose a threat. Furthermore, climate change is playing an increasingly significant role.

The IUCN Red List (International Union for Conservation of Nature) includes 26,197 species of threatened animals and plants, of which more than 8,000 vertebrate species are classified as vulnerable, endangered, or critically endangered (2,386 fish, 2,100 amphibians, 1,469 birds, 1,215 reptiles, and 1,204 mammals).