Why fire crews are using different tactics to stop flames from reaching California's ancient sequoias

Mariposa Grove in Yosemite National Park, where the biggest sequoia trees in the world grow, has been protected by the government for more than 150 years. 

That protection is now in the hands of firefighters who have been working around the clock to contain a wildfire in Yosemite National Park that is threatening the giant trees there. They are using different tactics that include using smaller fires to stop the Washburn Fire—which has burned more than four square miles of historic parkland and is now 22% contained. 

Thick plumes of dark smoke that triggered air quality alerts over the entire region was reportedly seen as far north as Oregon. Despite flames being attacked from all angles, the Washburn Fire continues to expand.