When a large number of species is lost over a relatively short time span,such as a few centuries,this situation is described as: 

A)  an eco-catastrophe 
B)  an extinction spasm 
C)  a major death sequence 
D)  an extinction sink

Extinction Spasm

Extinction Spasm is a rapid increase in the rate of extinction experienced by species within a relatively short geological period, often due to human activities.

Eco-Catastrophe

A major ecological disaster or event that causes significant harm to the environment and living organisms.