Sayonara?

According to the World Wildlife Foundation, the following 16 species are critically endangered:

Amur Leopard

Black Rhino

Cross River Gorilla

Hawksbill Turtle

Javan Rhino

Leatherback Turtle

Mountain Gorilla

Saola

South China Tiger

Sumatran Elephant

Sumatran Orangutan

Sumatran Rhino

Sumatran Tiger

Vaquita

Western Lowland Gorilla

Yangtze Finless Porpoise

What reasons may be given to explain why efforts should be made to preserve a species?

How are these reasons different from those used to explain why efforts should be made to preserve a critically endangered language?