Population Decline

Species extinction is the most visible metric but understates the crisis. Population decline within surviving species is equally alarming. The 2024 Living Planet Index tracks almost 35,000 vertebrate populations and found an average decline of seventy-three percent between 1970 and 2020.

Functional extinction occurs when a species still exists but in such small numbers that it no longer performs its ecological role. The functionally extinct species is a ghost — present in census counts but absent from the ecosystem's actual operations.