Human activities, especially habitat destruction, may cause 20% of all present species to be extinct within 30 years.
(Human activities; may cause; 20% of all present species; to be extinct within 30 years) (20% of all present species; to be; extinct; T:within 30 years)
Human activities 20% of all present species
may cause to be
20% of all present species to be extinct within 30 years
extinct T:within 30 years