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 on Tuesday.

 

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.

 

The IUCN said in a report that 34 percent of conifers were at risk of extinction, up from 30 percent in the last assessment in 1998.

 

California's Monterey Pine, the world's most widely planted pine and prized as a fast-growing source of pulp, was moved to a rating of "endangered" from "least concern" because of threats such as a spread of fungal disease.

 

Conifers are the largest and longest-lived species on the planet. The Bristlecone Pine can live 5,000 years and the Coast Redwood can grow as high as 110 meters (360 ft).

 

Diseases are compounding existing threats from logging, pollution and forest clearance caused by a rising human population. And global warming might be making conifers, standing in the same place for hundreds or even thousands of years, vulnerable to new pathogens as temperatures and rainfall patterns changed, he said.

 

The report said there were some successes. Better management and plantings of disease-resistant stock of Lawson's Cypress in California and Oregon had helped a recovery of trees that were once heavily traded as timber.