A grass fire travels at speeds of over 14 mph or 1232 feet per minute (ft/min). Although wood mulch is also flammable, it has many benefits that may make it a viable option in the overall big picture.
Flame height and temperature values for wood chips, at a 2– to 3–inch depth produce relatively low flame heights and rates of fire spread. Composted wood chips demonstrate the slowest fire spread rate of all wood mulch treatments at less than 0.3 ft/min. Fire rate of spread values are an approximation. Wood chips also produced the shortest average maximum flame height (note: flaming combustion was rare).
Although, wood mulch is flammable, take the time to evaluate the long term benefits and decide if it is right for your application.
Benefits of mulch:
Retains soil moisture by 80%
Reduces soil temperature by 25%
Suppresses weed growth
Study conducted by University of Reno Nevada.