LIGHTNING CAN STRIKE DOWN AND SET A TREE ON FIRE
SPARKS FROM ROCKFALLS CAN CAUSE IT ASWELL
SOME FOREST FIRES ARE FROM SPONTANEOUS COMBUSTION, THIS OCCURS WHEN THE TREES START TO PRODUCE HEAT AND DRY OUT ENOUGH TO CATCH FIRE, THIS HAPPENS WITH HAY, CHARCOAL AND COAL MOSTLY.
VOLCANO AND SPARKS FROM IT CAN CAUSE FIRE THE SAME WAY IT WOULD BURN THE GROUND AND HOMES.
Arson is one of the biggest human factors to cause, Arson is basically the fancy term for lighting stuff on fire, like a campfire and I think you know how that can start a Wildfire
Some Dead Cigarettes may still contain sparks that can light dried leaves or grass that will then spread into something even worst
Now yes this photo is fake but it helps show what Electric Arcs are. Electric Arcs are caused when an electrical discharge occurs usually between power lines and then a glow of electricity connects the two, like the finger and thumb in the photo. Now this can cause fires the same way lightning does. If the discharge attracts to a branch then it will set the branch on fire
Another way is from sparks from equipment, this sorta falls into the arson category because flint and steel is a tool made to make sparks to set stuff aflame. But during construction or mining sparks can be caused when hitting a rock sometimes or if friction occurs between two objects.
Heat waves, droughts, and Climate change like El Nino can occur, this also is a cause of global warming.
Plants tend to grow faster and sprout quickly after a wildfire, only a about a year it isn't instant but it is pretty fast for what used to be up in flames. Mostly because the ashes turn into fertilizer
Like green house gases the burning of the tree's cause the same effect heating the world
And obviously smoke in the air that isn't that great to inhale and it can spread to homes and buildings burning them and injuring or possible killing the people inside