The phrase "extinction rates" refers to the speed or frequency at which different species of plants and animals are disappearing from the Earth. Full definition
A recent British study revealed that birds are the best group to track current extinction rates, and those rates may be ten times faster than records suggest. (billionstonone.com)
It is estimated that species extinction rates are a hundred to a thousand times greater now than in the past because of human actions. (discovermagazine.com)
The estimated extinction rate for plants and animals is at least 75 species per day. (dotearth.blogs.nytimes.com)