“Dragon eggs” ignite after hitting the ground.
Trees and shrubs are invading the grasslands of the Great Plains. It has long been known that periodic fires are an effective way to drive these woody plants out, clearing the way for fast-growing grasses, but these fires need to be blazing to destroy certain stubborn, deeply-rooted shrubs
The problem, according to ecologist Dirac Tidwell of the University of Nebraska, is that the controlled fires normally set by ranchers and wildlife managers are insufficient to reverse the shrub infiltration. To ensure the safety of ground crews and the containment of the fires, they are normally carried out when temperatures are cool, winds are gentle, and the soil is moist from recent rain. This is in stark contrast to historical periodic grassland fires, which tended to occur during droughts or heavy winds.
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To simplify the task of fire distribution, Tidwell and his colleagues have developed, and recently carried out two field trials, on fireball igniters called “dragon eggs,” which get dropped out of an unmanned vehicle or drone. The balls contain a liquid that, once injected with alcohol, starts a chemical reaction causing them to ignite after hitting the ground, lending new fuel to the fire.
According to a review article published by Tidwell and his colleagues in Frontiers in Ecology and the Environment, using drones to set prescribed fires is a safer and cheaper alternative to the current methods of setting them by hand or by helicopters.
Unmanned vehicles also have the potential to help scientists gather data about wildfires that would be difficult to collect from the ground. "Understanding the spatial context and intensity of fires matters whether your goal is to protect a house or restore a grassland ecosystem," Tidwell said in a press release.
Watch a video of the dragon egg field trials: