Humans are the largest contributor to the start of wildfires. Human causes of wildfire include equipment malfunction, discarded cigarettes, unattended campfires, burning debris, vehicles, prescribed burns, and arson.
Wildfire smoke, exacerbated by climate change, is undoing decades of progress in improving air quality in the United States, posing significant health risks, and highlighting the need for comprehensive solutions.
Research shows that changes in climate create warmer, drier conditions, leading to longer and more active fire seasons. Increases in temperatures and the thirst of the atmosphere due to human--caused climate change have increased aridity of forest fuels during the fire season.
Fires tend to spread in the same direction as the ambient wind – usually uphill. Therefore, wildfire spreads more quickly uphill. This is also because the rising smoke and heat dry out the fuel further up the slope. Conversely, fires spread slower downhill because it cannot preheat the downhill fuel as effectively.
However, this can vary hugely depending on a number of factors, such as weather conditions, fuel type, and terrain.As a fire spreads over brush and trees, it may take on a life of its own -- finding ways to keep itself alive, even spawning smaller fires by throwing embers miles away.