A third of the world’s conifers, the biggest and longest-lived organisms on the planet, are at risk of extinction, with logging and disease the main threats, scientists said.

The study of more than 600 types of conifers – trees and shrubs including cedars, cypresses and firs – updates a “Red List” on which almost 21,000 of 70,000 species of animals and plants assessed in recent years are under threat.