Over 500 firefighters battle wildfire to protect trees in US Yosemite National Park

Authorities have said that more than 500 firefighters are battling a fast-moving wildfire to protect some of the world's oldest and largest trees in Yosemite National Park, one of the most visited national parks in the US.

The Washburn Fire, reported on Thursday afternoon, has grown to more than 2,340 acre (around 9.47 square km) and is only 25 per cent contained, threatening the Mariposa Grove of Giant Sequoias, the largest sequoia grove in the park.

Located in the southern portion of Yosemite, the historic tree grove is home to more than 500 mature giant sequoias, including the 3,000-year-old Grizzly Giant tree.

"A full initial attack response was dispatched, including Yosemite National Park Fire resources and state and local cooperators," said an incident update released by the InciWeb, an interagency all-risk incident information management system in the US.

A total of 545 firefighters are working at the scene, an increase of 185 personnel compared to Monday, Xinhua news agency reported.

The fire was active on Sunday evening and with the current warming trend, increased fire activity is expected for Monday as well, officials added.

While structure wrap is not currently being used on the giant sequoias, firefighters are proactively protecting the Mariposa Grove through the use of a ground-based sprinkler system.

This increases the humidity in the area around the trees and combined with the removal of ground fuel, the ground fire risk is greatly reduced, according to the update, adding that Yosemite's fire management programme has for many years utilised a wide variety of methods to reduce the fuel and minimise the risk of fire to more than 500 mature giant sequoias as well as the entire national park.