Missouri's natural communities have been shaped by humans and wildland fires for thousands of years. In many ways, the history of fire in Missouri also is a history of human population, culture and migration. Fires caused by natural ignition, like lightning, are rare. Despite as many as 50 to 70 thunderstorm days per year, Conservation Department studies indicate that less than 1 percent of modern day fires are started naturally. Humans have been, and continue to be, the primary cause of most wildland fires in Missouri.