Habitat destruction: The destruction of natural habitats is a major cause of extinction. When animals' homes are destroyed, they may not be able to find food, shelter, or mates, and their population can decline.
Climate change: Climate change can cause changes in temperature, precipitation, and sea level that can make it difficult for animals to survive. For example, rising temperatures can cause polar bears to lose their sea ice habitat, and changes in precipitation can affect the availability of food for desert animals.
Disease: Disease can spread quickly through animal populations and cause widespread death. For example, the bubonic plague killed millions of people in Europe during the Middle Ages, and the chestnut blight killed billions of chestnut trees in North America in the early 1900s.
Invasive species: Invasive species are non-native species that have been introduced to an area and have become a threat to native species. Invasive species can compete with native species for food and habitat, and they can also carry diseases that can harm native species. For example, the introduction of the cane toad to Australia has had a devastating impact on native frog species.
Predation: Predation is a natural process, but when human activities alter the balance of predator-prey relationships, it can lead to extinction. For example, the introduction of predators such as cats and dogs to islands can decimate native bird populations.