Some species live everywhere. Others live in one place and nowhere else. Those are endemic species, found naturally in only one specific region. The region can be large, like a continent, or tiny, like a single mountain top or cave. Endemism is common on islands, in isolated lakes, and on mountaintops where populations have been separated long enough to evolve into distinct forms. Madagascar is a classic example. Around 90 percent of its wildlife is found nowhere else on Earth, including all lemurs and most of its orchids.

Endemic species are often vulnerable. Their limited range means a single threat, like a hurricane, a fire, or an invasive predator, can wipe them out. Island species evolved without many mainland predators and often lack defenses. The dodo, a flightless bird endemic to Mauritius, went extinct within a century of human arrival. Habitat loss, climate change, and introduced species continue to threaten endemics today. Protecting them usually means protecting the specific place they live, which makes conservation a local matter as much as a global one.

Where endemism is high

• Islands: Madagascar, Hawaii, Galápagos.
• Ancient lakes: Lake Baikal, Lake Malawi.
• Mountaintops: sky islands in the Rockies and Andes.
• Caves and isolated springs.

Endemic species are irreplaceable. Once they are gone, they are gone everywhere, not just locally.