Washington, May 19: Over the last decade, an average of over 61,000 wildfires have burnt 7.2 million acres per year in the United States. When a wildfire begins to expand, the firefighting work is complicated by challenges such as spot fires, which occur when winds lift lofted sparks and start new fires outside of the original fire perimeter. The greater the possible spot fire distance, the more difficult it is to monitor, control, and extinguish wildfires.